Including Command Reference for
Firmware Version 1.1.8
Tucson Amateur Packet Radio TNC 2 System Manual
Copyright (c) 1985, 1990, 1991, 1992
Tucson Amateur Packet Radio Corporation
P.O. Box 12925
Tucson, AZ 85732-2925
(602) 749-9479
FAX (602) 749-5636
All rights reserved.
Reproduction or translation of any part of this work beyond that
permitted by Sections 107 or 108 of the 1976 United States
Copyright Act (or its legal successor) without the express
permission of the copyright owner is unlawful except as noted
below. Requests for permission to copy or for further
information should be addressed to Tucson Amateur Packet Radio
Corporation.
Except as noted above, permission is hereby granted to any
non-profit group or individual to reproduce any portion of this
document provided that: the reproduction is not sold for profit;
the intent of the reproduction is to further disseminate
information on packet radio; the reproduction is not used for
advertising or otherwise promoting any specific commercial
product; and full credit is given to Tucson Amateur Packet Radio
Corporation (including address) as the original source of
information.
August 1985
TNC 2 SOFTWARE SOURCE CODE and TNC FIRMWARE
Copyright (c) 1985
Systek
All rights reserved.
Reproduction or translation of any part of this work beyond that
permitted by Sections 107 or 108 of the 1976 United States
Copyright Act (or its legal successor) without the express
permission of the copyright owner is unlawful except as noted
below. Requests for permission to copy or for further
information should be addressed to Tucson Amateur Packet Radio
Corporation.
ii
Tucson Amateur Packet Radio TNC 2 System Manual
FOURTH EDITION
1992
The information contained in this document has been carefully
checked and is believed to be entirely reliable. However, no
responsibility is assumed for inaccuracies. Tucson Amateur
Packet Radio Corporation (TAPR) reserves the right to make
changes to any products to improve reliability, function or
design without obligation to purchasers of previous equipment.
TAPR does not assume any liability arising out of the application
or use of any product or circuit described herein; neither does
it convey any license under its patent rights or the rights of
others.
The Tucson Amateur Packet Radio Terminal Node Controller Model 2
project was made possible through the selfless dedication of many
individuals. These people represent the highest ideals of
volunteerism and public service, giving of themselves for the
benefit of the Amateur Radio community worldwide. It is on this
basis that TAPR exists, and it is on this basis that Amateur
packet radio has flourished during the past few years.
It is not possible to document the specific contributions of
every participant in TNC 2's development, nor even to list
everyone who made a contribution. However, the following list
includes those without whose efforts the project would not have
been possible.
Peter Eaton, WB9FLW Circuit board layout
Howard Goldstein, N2WX Software design
Steven Goode, K9NG Modem
Charles Green, N0ADI Documentation
Lyle Johnson, WA7GXD Documentation
Daniel Morrison, KV7B Testing
Margaret Morrison, KV7D Documentation
Paul Newland, AD7I Hardware design
Harold Price, NK6K Protocol
To the above list must be added those who were involved in the
Beta Test of the TNC 2 design: Paul Barnett, N0CRN; Jon Bloom,
KE3Z; Mike Brock, WB6HHV; Tom Clark, W3IWI; John Conner, WB0FHG;
Terry Fox, WB4JFI; Andy Freeborn, N0CCZ; Eric Gustafson, N7CL;
Skip Hansen, WB6YMH; Phil Karn, KA9Q; Scott Loftessness, W3VS;
Hank Magnuski, KA6M; Bill Reed, WD0ETZ; Gwyn Reedy, W1BEL;
Russell Reiss, K1HOP; Jeff Ward, K8KA.
The TNC 2 project would never have taken place without the
success of the TNC 1 project. In addition to many of those
listed above, the following people contributed to making TNC 1 a
recognized standard of Amateur packet radio: Mark Baker; Marc
Chamberlin, WA7PXW; Den Connors, KD2S; David Henderson, KD4NL;
Heather Johnson, N7DZU.
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Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 1 INTRODUCTION
Welcome to the exciting world of Amateur packet radio. You will
soon be joining the ranks of the fastest growing mode in Amateur
Radio since 2-meter FM.
The purpose of the Tucson Amateur Packet Radio (TAPR) Terminal
Node Controller (TNC) is to act as an interface between your
ordinary voice radio, such as a 2-meter FM transceiver or HF SSB
transceiver, and your computer. The TNC will perform all of the
"magic" of establishing error-free communications between your
station and another packet-radio equipped station. You will be
able to have a "private channel" while sharing a frequency with
other packet stations, "read the mail" or other QSOs, operate
remote computer "bulletin board" or "mailbox" stations, handle
message traffic -- in short, be able to enjoy all the advantages
of digital communication techniques in your ham shack.
Your TAPR TNC 2 is the key to your packet station. It is based
on the original TAPR TNC and inherits many of the advanced
features of that design, coupled with the experience gained by
thousands of TAPR-equipped Amateur packet stations worldwide.
This manual will be your guide into the realm of Amateur packet
radio. The Assembly Manual will take you step by step through
the construction and testing of your TNC. You will then be ready
to start with Chapter 2, which explains how to connect your TNC
to your station computer. Chapter 3 will instruct you on
interfacing the TNC to your radio and Chapters 4 and 5 will guide
you through packet radio operation. Chapter 6 is a detailed
breakdown of the various commands the TNC will accept and
messages it may report. A description of the hardware design of
TNC 2 and troubleshooting hints follow in Chapters 7 and 8. The
manual concludes with Chapter 9, an overview of packet radio
protocol. The Bibliography lists sources of further information
on packet radio.
What is TAPR?
Tucson Amateur Packet Radio is a non-profit research and
development group dedicated to the advancement of Amateur digital
communications. Its technical "staff" consists solely of
volunteers who donate their time in pursuit of TAPR's goals. TNC
2 was designed by such volunteers. TAPR is a membership
organization with members spread around the globe. The quarterly
Packet Status Register carries technical and operational
information on packet radio, Further, it is the means by which
TAPR provides support for your TNC 2. We encourage you to join
1
Tucson Amateur Packet Radio TNC 2 System Manual
TAPR and share with us in the development of this exciting mode.
Join the Packet Radio Revolution!
First Steps
Refer to the Assembly Manual included with your TNC 2 board and
follow the directions given. When you have completed
construction, continue with Chapter 2, Computer Interfacing.
Build your TNC 2 carefully and...
... happy packeting!
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Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 2 COMPUTER INTERFACING
Before beginning this chapter, you should have assembled your TNC
2 and verified that the power supply is functioning and that
various of the LEDs function properly. You will now attach, or
interface, your TNC 2 to your station computer or terminal.
Throughout this manual we will use the term "computer" to refer
to the computer or terminal you use to communicate with your TNC.
TNC 2 communicates with your computer through a serial port using
signals corresponding to a standard called RS-232C. Why an
RS-232C interface? Nearly every computer in production today
either incorporates an RS-232C style serial port as a standard
feature, or has one available as an optional accessory, either
from the computer manufacturer or from a manufacturer of computer
accessories.
In order to use the TNC with your computer, the computer must
have an RS-232C serial port and a program to support the serial
port. The program will typically be called a modem, terminal
emulator, or communications program.
Since there are so many computers on the market today, it is
impractical for this chapter to provide detailed instructions for
each computer. Detailed information is given for some of the
popular models available in the United States. Also provided is
general computer interfacing information.
Serial Port Signals
The serial port connector on your TNC is on the rear panel and is
marked "SERIAL." There are several signals available at this
connector. You won't need all of them for standard packet
operation. For some special applications, such as binary file
transfer or some Bulletin Board operations, you may want to use
more of them. In that case, see TNC 2 Serial Port Pin Functions
at the end of this chapter.
The pins on the serial port connector of TNC 2 that must be
connected are shown in Table 2-1. Note that the TNC connects to
a computer exactly as if the TNC were a standard RS-232C modem.
If you have successfully used your computer with a telephone
modem, hook it up to TNC 2 in the same way. Use whatever program
you ordinarily use to communicate with the modem and proceed to
the section, Verifying Serial Port Operation.
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Tucson Amateur Packet Radio TNC 2 System Manual
Table 2-1. Serial port signals required by TNC 2.
Pin Signal Name Description
2 Transmit Data Serial data from your computer
to the TNC.
3 Receive Data Serial data from the TNC to
your computer.
7 Signal Ground The common ground for both
data lines.
If your computer is listed in Table 2-2, refer to the specific
information in the following sections to connect your TNC to your
computer.
Table 2-2. Computers with specific serial interfacing
instructions.
Manufacturer Model
Apple Macintosh (tm)
Commodore VIC-20 (tm)
64 (tm)
IBM PCjr (tm)
Radio Shack Color Computer (tm)
Color Computer 2 (tm)
Model 100
NEC 8201
Many computers require a serial port adapter card. These cards
incorporate the circuitry necessary to add an RS-232C port to the
computer. Some popular models in this category are the Apple II
series, the IBM Personal Computer, many Radio Shack computers,
and the Sanyo MBC-55X series. If you have one of these computers
with an "add-in" serial port, or if you have another computer we
haven't mentioned, you should skip to one of the sections on
"other computers." If your computer has a 25-pin RS-232C serial
port, refer to the section Other Computers with 25-pin RS-232C
Ports. Otherwise refer to the section Other Computers with
Nonstandard Serial Ports.
Some computers have no serial port and no adapter is commercially
available. Such computers are not suitable for use with TNC 2.
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Tucson Amateur Packet Radio TNC 2 System Manual
Apple Macintosh
The Macintosh serial port is an RS-422 compatible port, but it
will work fine with the RS-232C serial port on your TNC. You will
need a cable wired as shown in Fig. 2-1.
Note that pin 1 is not connected inside the Macintosh or the TNC.
If you use a shielded serial cable, which we recommend, connect
both pin 1s to the shield and connect pin 1 of the TNC 2 serial
connector to digital ground on the TNC circuit board. A printed
circuit board pad is provided for this purpose near pin 1 of the
serial connector.
Commodore 64 or VIC-20
Commodore (as well as other manufacturers such as Jameco) sells a
voltage converter device that installs in the User port connector
on the rear of a VIC-20 or Commodore 64 computer. This adapter
converts the internal TTL-level voltages of the computer to the
proper RS-232C levels and polarities. Unless you are very
familiar with the inner workings of your computer, you should
purchase such an adapter rather than trying to "do it yourself."
IBM PCjr
The PCjr uses standard RS-232C voltage levels for its serial
interface; however, the connector used is non-standard and not
readily available from electronic supply dealers. Pinout
information for this connector is given in the IBM PCjr Technical
Reference Manual.
IBM dealers sell the "IBM PCjr Adapter Cable for Serial Devices"
for converting the connector on PCjr to a standard RS-232C
terminal connector. This cable attaches directly between the TNC
and the PCjr. It is only about 3 inches long, however, so you
5
Tucson Amateur Packet Radio TNC 2 System Manual
may want to obtain a male-to-female RS-232C extension cable,
which should be readily available.
Radio Shack Color Computer
The Color Computer series (except for the Micro Color Computer)
uses a 4-pin DIN-style connector for its serial interface. Wire
a cable as shown in Fig. 2-2 to interface your TNC to a Color
Computer. All necessary parts should be available from Radio
Shack dealers.
Fig. 2-2. Serial port wiring for Radio Shack
Color Computers.
Radio Shack Model 100 and NEC 8201
These computers have built-in standard RS-232C serial ports that
are compatible with the TNC. You will need a standard
male-to-male RS-232C extension cable to connect the computer to
the TNC.
Other Computers with 25-pin RS-232C Ports
If your computer has a 25-pin RS-232C port, you should consult
your computer manual or accessory manual to see which pins it
uses to send and receive data on, as well as which pin is used
for signal common. Follow the computer manufacturer's
recommendations for connecting the serial port to a modem. You
may also find the technical information in this section useful.
Your TNC is configured as Data Communications Equipment (DCE),
the technical term for an RS-232C modem. Most computers are
configured as Data Terminal Equipment (DTE). If this is the case
for your computer, you will probably be able to simply wire pin 2
of the TNC connector to pin 2 of your computer's RS-232C port,
pin 3 to pin 3 and pin 7 to pin 7. You can provide these
connections with a standard 3- wire male-to-female or
male-to-male RS-232C extension cable, depending on whether your
computer has a DB25S or DB25P connector.
6
Tucson Amateur Packet Radio TNC 2 System Manual
If your computer is configured as DCE, you will have to wire pin
2 of your TNC to pin 3 of the computer connector, and pin 2 of
the computer connector to pin 3 of your TNC. Pin 7 of the
computer connector will still connect to pin 7 of your TNC serial
port.
Some computers may require that pin 5 of the computer serial port
connector be connected to an appropriate signal. Others may
require connections for pin 8 and pin 20. You can use the
computer's output signals on pins 4 and 6 as shown in Fig. 2-3.
Fig. 2-3. Serial port wiring with jumpers for
auxiliary signals.
Other Computers with Nonstandard Serial Ports
Computers with nonstandard serial ports must meet the following
conditions.
First, the signal levels should be RS-232C compatible. The TNC
requires that the voltage levels sent from the computer be
greater than about +3 volts in one state and less than about +1
volt in the other state.
Second, the polarity of the signals must conform to the RS- 232C
standard. This means that the low voltage state must correspond
to a logical "1" and the high voltage state to a logical "0".
Third, the computer must be able to correctly receive a signal
which meets the RS-232C specification. The TNC supplies signals
that meet this specification.
Make or buy a cable that provides the following connections. The
computer serial port common pin must be tied to the TNC serial
port connector pin 7. The data line that sends data from the
computer must be tied to the TNC connector pin 2. The pin on
which your computer receives data on must be tied to the TNC
connector pin 3.
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Tucson Amateur Packet Radio TNC 2 System Manual
If your computer requires any other signals, you must arrange to
provide them. The documentation provided with your computer or
its accessory serial port should clarify any special requirements
of your port.
Software Requirements
Any software package that enables your computer to act as an
ASCII terminal with an ordinary telephone modem should work with
your TNC. If you have a program that you have used successfully
with telephone a modem and that you are familiar with, use that
program to communicate with your TNC.
Apple Macintosh
Apple dealers sell a program called MacTerm for the Macintosh
that works with the TNC. Load this program and set the options
according to Table 2-3. In addition, set the TNC for 1200 baud
as described in Verifying Serial Port Operation, below.
Table 2-3. MacTerm option settings for operation
with TNC 2.
Compatibility Terminal
1200 baud VT100
7 bits/character ANSI
even parity UNDERLINE
Handshake Xon/Xoff US
modem connection 80 Columns
"telephone" port ON LINE
AUTOREPEAT
Commodore 64 or VIC-20
A BASIC communications program is given in the Programmer's
Reference Guide published by Commodore. Use the program listing
for "true ASCII," as these computers use a modified ASCII format
internally. You will probably want to run your TNC at 300 baud
on the serial port with these computers. Setting the TNC serial
port baud rate is discussed in the next section, Verifying Serial
Port Operation.
IBM PCjr
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Tucson Amateur Packet Radio TNC 2 System Manual
The IBM PCjr has a built-in terminal program in the BASIC
cartridge. Start this program by typing TERM. Refer to your
PCjr BASIC manual for details on this program. For best results
with PCjr, do not run the TNC serial port faster than 1200 baud.
Setting the TNC serial port baud rate is discussed in the next
section, Verifying Serial Port Operation.
Radio Shack Color Computer
There are several terminal programs available for the Color
Computer. You will probably want to use a commercial program
(rather than writing your own) since the Color Computer has a
"software UART" that is difficult to program in BASIC.
Radio Shack Model 100 and NEC 8201
These computers have built-in terminal programs in ROM. Consult
your computer's documentation for instructions in their use.
Verifying Serial Port Operation
Turn off the power to your computer and to your TNC. Connect the
computer and TNC with a properly configured serial cable. Set
the DIP switch on the rear panel of the TNC to the desired baud
rate as shown in Table 2-4. The power must be OFF when these
switches are set.
NOTE: The serial port baud rate used between the TNC and the
computer has no relationship to the baud rate used over the
radio. The serial port baud rate you set on your TNC must match
the baud rate used by your computer serial port.
Table 2-4. DIP switch settings for serial port
baud rates.
Baud Rate Switch 1 2 3 4 5
300 ON OFF OFF OFF OFF
1200 OFF ON OFF OFF OFF
2400 OFF OFF ON OFF OFF
4800 OFF OFF OFF ON OFF
9600 OFF OFF OFF OFF ON
CAUTION: Only one of these switches may be ON at any time.
Turn on your computer and start the terminal program. Follow the
directions for the program you are using to match the computer's
9
Tucson Amateur Packet Radio TNC 2 System Manual
baud rate with that selected on the TNC, and to set other
options. Set your computer's port options to 7 bits even parity
and select either 1 or 2 stop bits.
Turn on your TNC. You should see a sign-on message, which should
be a readable text message, printed on your computer screen.
This demonstrates the ability of your computer to accept data
from your TNC. If you see nothing, switch off your TNC for a few
seconds, then on again. If you still see nothing, verify your
wiring and restart your terminal program. If you see gibberish
on your screen you should verify that you have set the same baud
rate for the TNC and the computer.
When you have successfully read the sign-on message from your
TNC, type
DISPLAY
followed by a carriage return. You should see a lengthy list of
items on your screen. This verifies the ability of your TNC to
accept and respond to input from your computer.
Your serial interface is now working. If you are completing
construction of your TNC, return to the assembly manual and
continue from where you were directed to this manual.
TNC 2 Serial Port Pin Functions
This section describes the pins used on the TNC's RS-232C serial
port connector. It is intended for packet operators with special
applications requiring hardware handshaking. This information
should not be needed by most users.
Table 2-5. RS-232C Pin Designations
Pin Mnemonic Name
1 FG Frame Ground
2 TXD Transmit Data
3 RXD Receive Data
5 CTS Clear To Send
6 DSR Data Set Ready
7 SG Signal Ground
8 DCD Data Carrier Detect
9 --- + 12V unregulated reference
10 --- - 12V unregulated reference
20 DTR Data Terminal Ready
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Tucson Amateur Packet Radio TNC 2 System Manual
Frame Ground is provided for attachment to the chassis of the TNC
and the chassis of the attached device (computer or terminal).
This pin is brought out to a feedthrough on the TNC 2 PC board
near pin 1 of the serial connector. It is not electrically
connected anywhere else on the TNC circuit board.
Transmit Data is an input line to the TNC on which the attached
device sends data.
Receive Data is an output line from the TNC on which the attached
device receives data.
Clear To Send is an output from the TNC signaling the attached
device to send or refrain from sending data to the TNC. This
line is used for hardware flow control.
Data Set Ready is an output from the TNC telling the attached
device that the TNC is operational.
Signal Ground is the common, or return, path for all signals
between the TNC and the attached device.
Data Carrier Detect is an output from the TNC. As normally
configured, DCD reflects the status of the CON LED: It is true
when an AX.25 connection exists between your TNC and another
station; it is false when no connection exists. This
configuration is useful when the TNC is used with a telephone
style Bulletin Board system, since the AX.25 connection, analo-
gous to a modem signal on the telephone, indicates the presence
of a user. Shorting JMP1 on the TNC 2 PC board will cause this
output to always be true.
Pins 9 and 10 provide access to the TNC's unregulated +/-12 volt
supplies for use by an external device. These are not intended
to power an accessory, and should not be used to source or sink
more than a couple of milliamperes!
11
Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 3 RADIO INTERFACING
Computer interfacing, covered in the previous chapter, is only
half the interfacing task. The other half is connecting your TNC
to a radio.
Before you interface the TNC to your radio you should calibrate
your modem frequencies. If you have just assembled your TNC, you
should have done this as part of the assembly procedure. The
complete modem calibration procedure is described in Chapter 5.
Interfacing the TNC to your radio involves connecting the
following signals at J2.
Pin 1 Microphone audio, from the TNC to your transmitter.
Pin 2 Ground, audio and PTT common.
Pin 3 Push-to-talk, to allow the TNC to key your transmitter.
Pin 4 Receive audio, from your receiver to the TNC.
Pin 5 Squelch input (optional) to allow the TNC to detect
activity on a shared-mode channel.
This chapter describes how to connect these signals between your
TNC and your radio and how to adjust the receive and transmit
audio levels appropriately. The interconnection should be
planned so as to minimize pickup of stray audio and RF noise by
the lines. If possible, you should set up your packet station
with a monitor speaker and be able to operate on voice without
disconnecting the TNC.
This chapter assumes that you are using an FM radio. If you are
operating on another mode, such as SSB, most of the information
is still applicable.
Two interfacing methods are presented. You will have to use the
second method if you can't adjust the audio levels properly with
the first method. They require no special test equipment for
adjusting the audio levels. If FM test equipment is available,
however, it should be used as described. You will need a second
receiver in your shack that you can use to listen to your own
signal. Read the remainder of this chapter carefully before
starting to interface your TNC to your radio.
12
Tucson Amateur Packet Radio TNC 2 System Manual
Method 1: Direct Connection to Microphone and Speaker
TNC 2 was designed to allow hookup and initial testing to be done
without any modifications to the radio or any signal level
balancing devices in the cables.
For Method 1, the TNC's audio will be fed directly into the
microphone connector or similarly connected auxiliary jack, and
the output of the TNC will be adjusted to give a proper
modulation level. The receiver audio will be taken from an
earphone plug or speaker jack and fed directly to the TNC.
This method is expedient but, unless you have an auxiliary
speaker/mike jack, it doesn't allow you to monitor the channel or
to conveniently use the rig on voice. The connection may also be
susceptible to RFI from nearby Amateur and commercial trans-
mitters. For these reasons you may want to use the second
interface method for your permanent station interface, after the
initial testing phase.
Connect your TNC to your radio. Turn on your TNC and computer and
start your terminal program. Connect the radio to a dummy load
and listen to the transmission with another nearby radio.
1. Enter the modem calibration procedure by typing
CALIBRA
and a carriage return. Press the K key on your keyboard to key
the transmitter, then tap the space bar until the higher of the
two tones is heard. Pressing the K key again will unkey the
transmitter. After the transmitter has been keyed for a few
seconds, it will be shut off automatically by the transmit
watch-dog circuit. As you perform the adjustments below, you
will have to periodically unkey then re-key the transmitter by
typing the K key. If you wish to defeat the watch-dog timer,
place JMP4.
2. With the TNC keying the transmitter and transmitting the
higher of the two tones, adjust the transmit audio level as
follows. With a small screwdriver, adjust trimpot R76 while you
listen to the monitoring receiver. Turn the adjustment screw on
R76 clockwise (CW) until no increase in output level is heard at
the monitoring receiver.
3. Rotate the adjustment screw of R76 counterclockwise until
the audio signal on the monitoring receiver is slightly, but
noticeably, reduced from the maximum level.
13
Tucson Amateur Packet Radio TNC 2 System Manual
4. Press the K key to return to receive mode and type Q to exit
the calibration routine. Be sure to remove JMP4 if you placed it
to defeat the watch-dog timer. You have now set your transmitter
deviation to approximately the correct level.
5. With your radio in the receive mode, open the squelch con-
trol so that a steady hiss would be heard on a speaker. Set the
volume control so the DCD LED on your TNC flickers occasionally
with no received signal. This is approximately the proper level
for best receive performance from your TNC's modem.
If you notice a significant hum level in the monitored audio in
Step 3, take measures to remove it. This may require shielded
wire (recommended in any event) in your microphone audio circuit.
If your transmitter has an adjustable microphone gain control,
try reducing the sensitivity of the transmitter microphone
circuit and increasing the signal level from your TNC to minimize
hum or other noise problems.
Method 2: Accessory Jack or Interface Box Connection
If your radio has an accessory jack with PTT, transmit audio, and
receive audio signals, the interface can be done through this
jack with the addition of only a single resistor inside the
radio. This resistor should be placed in series with the TNC
audio output where it is connected to the microphone audio to
provide isolation. The method of determining the value required
will depend on the radio used, and is described below..
If your radio does not have an accessory jack and you don't wish
to add a connector to your radio, you should construct a separate
external interface box. This box will permit simultaneous
connection of your TNC and a microphone. Again, a series
resistor should be placed in series with the TNC audio output.
It will either have its own speaker or pass the speaker signal
through to a connector so that you can monitor the receive audio
while your TNC is hooked up.
Regardless of whether you use an accessory jack or an external
interface box, you should use shielded wire for all
signal-carrying leads. The connector types and pinouts will be
determined by the connector jacks on your radio.
When all required cables have been assembled and the TNC is
connected to the radio, you are ready to set the levels according
to the following procedure.
1. Remove the shunt attenuator element, R57 in the microphone
audio section of your TNC.
14
Tucson Amateur Packet Radio TNC 2 System Manual
2. Temporarily solder a variable resistor in place of R(S) in
Fig. 3-3 or Fig. 3-4. The maximum value of this resistor must be
determined by experiment, but 500K should handle most cases.
3. Connect your TNC to the radio. Connect the microphone to
the radio, or to the interface box if one is being used. Connect
the radio to a dummy load.
4. Turn on your TNC and computer and start your terminal
program. Enter the modem calibration procedure by typing
CALIBRA
Press the K key to key the transmitter, then tap the space bar
until the higher of the two tones is heard. Pressing the K key
again will unkey the transmitter. After the transmitter has been
keyed for a few seconds, it will be shut off automatically by the
transmit watch-dog circuit. As you perform the adjustments be-
low, you will have to periodically unkey then re-key the
transmitter by typing the K key. If you wish to defeat the
watch-dog timer, place JMP4.
5. With the TNC keying the transmitter and transmitting the
higher of the two tones, adjust the transmit audio level as
follows. With a small screwdriver, adjust trimpot R76 and set
the output of your TNC to about 70% of its maximum undistorted
value as observed on an oscilloscope monitoring the transmit
audio at JMP7. This level may be estimated without an
oscilloscope by turning R76 clockwise to maximum (indicated by a
clicking sound inside the trimmer) and then backing off 15 turns.
At this point the signal amplitude at JMP7 should be about 2.5
volts peak-to-peak.
6. Adjust the variable resistor installed in step 2 for proper
modulation level (typically between 3.0 and 4.5 kHz deviation for
Amateur FM). If FM test equipment is not available, adjust R(S)
as described in steps 2 and 3 of Method 1 above, using R(S)
instead of R76.
7. Press the K key to return to receive mode and type Q to exit
the calibration routine. You have now set your transmitter
deviation to approximately the correct level. Remove JMP4 if you
placed it in Step 4.
8. Carefully remove the variable resistor and measure its
value. This is the proper value of R(S) for your particular
radio.
15
Tucson Amateur Packet Radio TNC 2 System Manual
9. Select the nearest standard value fixed resistor (1/4 watt
is fine) and permanently install this resistor as R(S) in the
interface circuit.
10. If you have access to FM test equipment, check to see that
the modulation level is still within the limits of 3 to 4.5 kHz
deviation. If it is not, make a final adjustment with the TNC
transmit audio level control, R76.
11. Open the squelch control on your radio so that a steady hiss
is heard. Set the volume control so the DCD LED on your TNC
flickers occasionally. This is approximately the proper level
for best receive performance from your TNC's modem.
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Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 4 OPERATION I: GETTING STARTED
This chapter will guide you through the basics of packet radio
operation with TNC 2. Packet radio has a great deal of power and
flexibility, and this chapter only scratches the surface of your
packet station's capabilities. However, it contains the basic
information required to get you on the air with packet radio to
begin exploring this new mode.
First Steps
The serial port baud rate switches on the back of the TNC should
be set to the same baud rate as your computer. These settings
are described in Chapter 2, Computer Interfacing. Set the
following switches, with the TNC OFF (be sure only one of these
switches is ON when the TNC is powered up):
Table 4-1. DIP switch settings for 1200 baud
radio data rate.
Switch Setting
6 OFF
7 ON
8 OFF
This sets a radio baud rate of 1200 baud. The radio baud rate is
not related to the computer baud rate.
Turn on your TNC. You should see something like the following
display.
Tucson Amateur Packet Radio TNC 2
AX.25 Level 2 Version 2.0
Release nn
Checksum $xx
cmd:
The first five lines are the sign-on message, which you will
normally see only when you power up the TNC. (See the Software
Release Notes for values of nn and xx.) The Command Mode prompt
cmd: will appear when the TNC is in Command Mode and is ready to
accept your instructions.
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Tucson Amateur Packet Radio TNC 2 System Manual
You may see some anomalies in the appearance of the display,
which will be corrected as you proceed through the next section.
The sign-on message may appear double-spaced, or characters you
type may be displayed twice. You may even see incorrectly
displayed characters.
Entering Commands
In the examples in this chapter, text that you are supposed to
type will appear in boldface. Text typed by the TNC will appear
in normal type:
cmd:RESET
This means that you are supposed to type the text, "RESET",
following the Command Mode prompt which the TNC typed. End the
line with a carriage return. All command entries will end with a
carriage return, abbreviated <CR>. The <CR> at the end of a
command normally won't be mentioned.
You should see the TNC's response to the RESET command:
bbRAM loaded with defaults
Tucson Amateur Packet Radio TNC 2
AX.25 Level 2 Version 2.0
Release nn
Checksum $xx
cmd:
The TNC has reloaded all user-settable parameters normally stored
in the battery backed-up RAM (bbRAM). All parameters are now set
to their default values. The TNC has also re-initialized itself
exactly as it would upon power-up, and typed a sign-on message.
You probably won't use this command often. The TNC will
automatically reload the bbRAM at power up if it finds that the
data is bad.
If you make mistakes while entering commands to the TNC, you can
make corrections. To erase the last character you typed, enter a
<BACKSPACE> character. The TNC will throw away the last
character you typed (unless you are at the beginning of a line)
and try to erase the character from your screen. Input editing
will be discussed in more detail in the section, "Special Input
Characters."
You are now ready to start setting up the parameters you will
use. You may be satisfied with most of the defaults for now, but
a few parameters will have to be changed!
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Tucson Amateur Packet Radio TNC 2 System Manual
cmd:MYCALL WA7QST
was NOCALL
cmd:
Type the text, "MYCALL WA7QST", following the command mode
prompt. Of course, you should substitute your own call sign for
WA7QST. Don't forget the <CR> at the end of the line. Your call
sign will be used by the TNC as its "address." The TNC responds
by telling you the previous value of the MYCALL parameter, and
gives you a new Command Mode prompt.
Now try typing just the command by itself:
cmd:MYCALL
MYCALL WA7QST
You can see the current value of most parameters by typing the
command that sets the parameter followed by just a <CR>. This
verifies that the TNC accepted your call sign.
The next section describes the commands you will use to configure
the TNC for proper text display for your particular computer.
You may not use these commands again unless you change computers
or terminal programs. The following sections, "Basic Operation"
and "Monitoring Channel Activity," describe the commands you will
use for your everyday packet operations. With these commands you
will be ready for the section, "Your First Packet QSO." The last
section of the chapter, "Special Input Characters" contains
information on input editing and other special characters used by
the TNC.
If you intend to use your packet station for "advanced"
applications, such as a computer Bulletin Board or binary file
transfers, you should continue with Chapter 5, Operation II:
Further Details. However, Chapter 4 contains all the information
that is needed for most packet operations. For a full
description of all commands, refer to the appropriate entry in
Chapter 6, TAPR TNC 2 Commands.
Most commands can be abbreviated, and the minimum abbreviations
for each command are given in the listings in Chapter 6. For the
sake of clarity, only the full command names are used in this
chapter.
Serial Port Configuration
This section describes the commands you will use to set up your
TNC to work best with your computer.
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Tucson Amateur Packet Radio TNC 2 System Manual
Parity and Word Length
If messages from your TNC appear garbled, with incorrectly
displayed characters, you may need to change the TNC's serial
port parity and word length. (We assume that you have set the
baud rate correctly. See Chapter 2 if the baud rate needs to be
changed.) The most common parity and word length combinations
are 7 bits, even parity (the TNC default), and 7 bits, space
parity. The TNC default will probably be accepted even if your
computer actually uses the latter setting. If your computer
receives 8 bits as data, you may have to set space parity, since
text may otherwise be interpreted as graphics or other special
characters. To set 7 bits, space parity, use the following
combination:
AWLEN 8 (8-bit words)
PARITY 0 (no parity bit)
To return to 7 bits, even parity, set
AWLEN 7 (7-bit words)
PARITY 3 (even parity)
One of these combinations will satisfy most computers. You are
more likely to require a different setting if you have a terminal
rather than a computer, or if you have configured your terminal
port for some special application.
If your computer requires odd parity, set PARITY 1. If your
computer detects framing errors, try setting
AWLEN 7 (7-bit words)
PARITY 0 (no parity bit)
for shorter characters. For longer characters, set:
AWLEN 8 (8-bit words)
PARITY 1 or PARITY 3
Echos
You may see two characters on your screen for every character you
type, for example:
cmd:RREESSEETT
Your computer is echoing the characters you type, and the TNC is
also echoing them. In this case, set ECHO OFF to stop the TNC's
echos. If you later use your TNC with a different computer, or
20
Tucson Amateur Packet Radio TNC 2 System Manual
with a different terminal program, you may see nothing displayed
when you type. In that case, set ECHO ON.
New Lines and Line Wrapping
If everything displayed appears to be double-spaced, your
computer is adding an extra linefeed (<LF>) whenever it displays
a carriage return (<CR>). Set AUTOLF OFF to keep the TNC from
also adding an <LF>. If you change equipment you may have to set
AUTOLF ON to restore the TNC's automatic linefeeds.
The screen-width parameter is set by default to 80, the width of
many CRT displays. The TNC will send an extra <CR> (or <CR> <LF>
if AUTOLF is ON) when 80 characters have been displayed on a
line. If your computer does not automatically break long lines,
you will need to set the screen width to the width of your
display. For example, for a computer using a TV set for a
display, you would set SCREENLN 40. If your computer does
automatically break long lines, you should set SCREENLN 0 to
disable this feature on the TNC. Otherwise, you will get two
<CR>s when the line wraps around.
A few computers will frequently lose the first characters of a
line when several lines are typed in rapid succession, for
example, in the sign-on message. You can give the computer more
time between lines by setting NUCR ON (delay after <CR>), or NULF
ON (delay after <LF>). The delay is adjusted by NULLS, which
sets a number of character-times for the delay.
Basic Operation
You can learn quite a bit about your TNC's operation without
actually transmitting anything. For your first experiments, your
TNC will be "talking to itself," allowing you to become familiar
with it before you go on the air.
Disconnect your radio from your TNC and turn off the TNC.
Install the digital loopback jumper, JMP10. The analog loopback
jumper, JMP7, should not be installed. Connect your computer to
the TNC with your serial cable. Turn on the computer and start
your terminal program.
A Connecting and Disconnecting Exercise
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Tucson Amateur Packet Radio TNC 2 System Manual
Packet radio QSOs are started by a connect process, which sets up
the "handshaking" between the two stations that insures
error-free communications. QSOs are terminated by a disconnect
process, which leaves both stations free to start new QSOs.
Packet QSOs can also make use of digipeaters, other packet
stations which can automatically relay packets from one station
to the other over a specified route.
To see how this works, you can have your TNC connect to itself.
Since you have set the TNC up for digital loop-back, it will
receive all packets that it sends. Try the following:
cmd:CONNECT WA7QST
*** CONNECTED to WA7QST
replacing WA7QST with your own call sign. The TNC generates
packets initiating and confirming the connection. The packets
aren't actually converted to audio signals and transmitted over
the radio, but they are otherwise just like packets you will be
transmitting later on.
The *** CONNECTED to message tells you that the connection was
successful. You should also notice that the CON LED has lit up
and that you do not see a new cmd: prompt on the next line. You
are now in Converse Mode, ready to start talking. Try it. Type
your message, ending the line with a <CR>.
Hello, there.
Hello, there.
The <CR> causes your message to be put into a packet, or
"packetized," and transmitted. (We explain in the next chapter
how you can use a different character to send packets.) The
underlined text is a message that the TNC received in a packet
and displayed. Whenever you are in Converse Mode anything you
type will be assembled into a packet addressed to the station you
are talking to and transmitted. If there isn't a QSO (con-
nection) in progress, the packet will be sent to the address CQ.
In the example above, your TNC entered Converse Mode automa-
tically after the connect took place. You can also command the
TNC to move back and forth between Command Mode and Converse
Mode.
To return to Command Mode, you must enter a special character,
Control-C (abbreviated <CTRL-C>), or else send a BREAK signal.
"Control" characters are usually entered by holding down a
special control key and then typing another key without releasing
the control key. If your keyboard doesn't have a key marked CTRL
or something similar, consult the documentation for your computer
or terminal program to see how to enter control characters. A
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Tucson Amateur Packet Radio TNC 2 System Manual
BREAK signal is a special transmission (not an ASCII character)
which your computer may be able to produce.
NOTE: If <CTRL-C> will cause your computer to do something
to interfere with packet operations, such as halting the terminal
program, and you can't send BREAK signals, you will have to
change the character that returns you to Command Mode. See the
section on "Special Input Characters," below.
Now type a <CTRL-C>. The TNC doesn't echo the <CTRL-C>, but you
should immediately see a Command Mode prompt. To return to
Converse Mode, enter the command CONVERS:
<CTRL-C>
cmd:CONVERS
Whatever I type in Converse Mode is transmitted.
Whatever I type in Converse Mode is transmitted.
<CTRL-C>
cmd:
To terminate the QSO, you must end the connect by giving the
DISCONNE command. The TNC will transmit packets terminating the
conversation and notify you when the disconnect is complete:
cmd:DISCONNE
*** DISCONNECTED
An actual QSO might be terminated by the other station, of
course. In that case, you would see the *** DISCONNECTED message
without having issued the command.
You have just performed the basic operations of any packet QSO.
You established a connection with the desired station to begin
the QSO, sent and received some messages, and disconnected from
the station at the end of the QSO.
Digipeating
You may wish to have a QSO with another packet station that is
beyond your direct radio range. If a third packet station is on
the air and both you and the station you want to talk to are in
range of this third station, that station can relay your packets.
You set up the packet routing when you initiate the connection.
Your TNC will then automatically include the routing information
in the packets it sends.
The diagram below shows an example situation in which digipeating
is useful.
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Tucson Amateur Packet Radio TNC 2 System Manual
AD7I
/ \
N2WX _________/ \_________ WA7QST
You are station WA7QST, and you want to have a packet QSO with
N2WX. There is a mountain in the way and you are not in simplex
range of each other. However there is a station located on the
ridge, AD7I, which is in range of both you and N2WX.
You direct the TNC to set up a connection to N2WX using AD7I as
an intermediate digipeater as follows:
cmd:CONNECT N2WX VIA AD7I
You can specify a routing list of up to eight intermediate
stations. For example, consider a modification of the example
above:
AD7I has turned off his station, but you can contact N2WX by
going around the mountain through NK6K and KV7D. This time you
issue the connect command like this:
cmd:CONNECT N2WX VIA NK6K, KV7D
You specify the digipeaters in the order you would encounter them
going from your station to the station to which you wish to
connect.
Your station can also act as a digipeater for other stations.
This doesn't require any special actions on your part -- your TNC
will do everything automatically. If your station is
digipeating, you may occasionally notice your transmitter keying
during lulls in your own conversations.
Unsuccessful Connections
Sometimes you will initiate a connect sequence that can't be
completed. The station may not be on the air, or it may not be
within range of your station. You may have even mis-typed the
other call sign. If the TNC does not get a response to its first
connect packet, it will try again. You can control the number of
attempts the TNC will make with the command RETRY. The default
24
Tucson Amateur Packet Radio TNC 2 System Manual
number of retry attempts is 10. If the TNC doesn't get an answer
after this number of transmissions, it will give up and display
the message
*** retry count exceeded
*** DISCONNECTED
The retry count is also used once the QSO has started. Each
transmission sent to the other station is "acknowledged," or
ACKed by the other station, and vice versa. The ACK means that
the packet was received and that the CRC checksum indicated that
it was received without errors. This is the means by which
packet radio can ensure error-free communications. Sometimes a
packet won't be received correctly by the other station, either
because of accidental interference from another packet station (a
collision), or because of other channel noise. If your TNC
doesn't get an ACK soon enough, it retransmits the packet and
increments the retry count. If the count set by RETRY is
exceeded, the TNC will automatically disconnect and display the
same message:
*** retry count exceeded
*** DISCONNECTED
The automatic disconnect feature keeps a TNC from indefinitely
retransmitting a packet and tying up the channel under hopeless
conditions. For example, an intermediate digipeater might have
been shut down, or the RF channel might have deteriorated to the
point of being unusable. The other operator might have even
turned off his station without disconnecting. If you are
operating under special conditions, such as a marginal HF
channel, you can set RETRY 0 to disable all automatic disconnects
(the retry limit is never reached).
Monitoring Channel Activity
In addition to displaying messages from the station you are
connected to, your TNC can allow you to monitor other packet
activity on the channel. You can "read the mail," displaying
packets between other stations. Your TNC will also keep track of
stations heard during a session. This section will describe some
of the monitor functions.
Monitoring is enabled or disabled by the MONITOR command. You
can try this out in digital loop-back mode while disconnected.
Type:
cmd:MONITOR ON
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Tucson Amateur Packet Radio TNC 2 System Manual
cmd:CONVERS
This is a test packet.
WA7QST>CQ:This is a test packet.
Since you aren't connected to another station your packets are
sent to the address "CQ," i.e., anyone. The packet you sent was
"heard" by the TNC and displayed, along with the sending station
and the destination.
If you also want to see any intermediate digipeater stations
being used, you can set MRPT ON. This feature would be useful if
you later want to connect to one of the stations you are
monitoring and will need a digipeater route in order to reach it.
For example, you might see the following display:
WB6YMH>WD0ETZ,KV7B:Hello, Bill!
This packet was sent from WB6YMH via KV7B to WD0ETZ.
If there are several digipeaters, or if the message lines are
long, the display may be difficult to read. You can put the
address header on a separate line from the text by setting
HEADERLN ON:
WB6YMH>WD0ETZ,KV7B:
Hello, Bill!
Ordinarily, your TNC will stop displaying monitored packets if
you connect to another station, permitting you to converse
without interruption. If you want to monitor activity while
connected to a packet station, set MCON ON.
To display a list of stations heard since the last time your TNC
was powered up, type
cmd:MHEARD
AD7I
WA7GXD
N2WX
NK6K
KV7B*
The last several stations whose packets were heard by your TNC
are displayed. The entry "KV7B*" means that KV7B was heard
digipeating a packet rather than sending one of his own. You can
clear the "heard log" with the command MHCLEAR.
You can see the settings of the monitor parameters described
above, as well as several others, by typing DISPLAY MONITOR.
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Tucson Amateur Packet Radio TNC 2 System Manual
Your First Packet QSO
Although there are still a number of features you should be
familiar with for comfortable packet operation, you are probably
eager to get on the air and try out your TNC. Arrange to have
another packet operator get on the air to help you get started.
Make sure that your friend will be close enough to ensure solid
copy, with no FM "popcorn" noise. It's best if you can get an
experienced packet operator to help you get started. If you are
both beginners, try to have both stations in the same room and
operate on low power or into dummy loads.
Starting the QSO
You are ready to initiate a connect. For the sake of example, we
will continue to use WA7QST in place of your call sign, and we
will use WB0QRP for your friend's call. Make sure you are in
Command Mode, and type
cmd:CONNECT WB0QRP
After a moment you should see the message
*** CONNECTED to WB0QRP
and you will be in Converse Mode. Your friend will see the
message
*** CONNECTED to WA7QST
and he will also be in Converse Mode. You have begun your first
QSO.
If you have trouble connecting, make sure your microphone drive
level is set properly, as described in Chapter 3. It may be
helpful to have an experienced packet operator listen to your
transmissions and monitor with his TNC. You can also try the
following procedure. Both you and your friend should set MONITOR
ON, enter Converse Mode and send some packets. Each station
should display packets sent by the other. If only one station is
"hearing" properly, you can concentrate on the modulator and
transmitter of that station and the demodulator and receiver of
the other station. You can try experimenting with the TXDELAY
timing parameter for the sending TNC. Set TXDELAY 64 for a long
delay. If this solves the problem, you can back off to the
smallest value that works consistently.
27
Tucson Amateur Packet Radio TNC 2 System Manual
Exchange several messages to get a feel for this new mode. If
you monitor the radio transmit indicators and listen to the
speaker audio from the two rigs, you will have a better idea of
what is happening. You radio will be inactive most of the time,
even while you are actually typing. When you get to the end of a
line and type a <CR>, your radio will be keyed briefly and your
friend will hear a "brrrraaaap" on his speaker. As your message
is displayed on his computer, his radio will be keyed for an even
shorter time and you will hear a "brraap" on your speaker. This
is the ACK, or packet acknowledgment coming back. Your TNC takes
note that the packet was received correctly, but nothing is
displayed on your screen.
Digipeating
Now that you are on the air, you and your friend can try out the
TNC's digipeating capabilities. This is actually more
interesting if you have at least three stations participating,
but you can get the feel for it with two stations.
Return to Command Mode and disconnect from the other station:
<CTRL-C>
cmd:DISCONNE
*** DISCONNECTED
Now issue the following command.
cmd:CONNECT WA7QST VIA WB0QRP
As before, substitute your call for WA7QST and your friend's call
for WB0QRP. You are requesting a connect to yourself, as you did
before in digital loop-back mode, but this time you are using a
sort of RF loop-back. You transmit packets to your friend's TNC,
which relays them back to you. When the connection is
established you will see
*** CONNECTED to WA7QST VIA WB0QRP
and you will be in Converse Mode. Your friend won't see anything
displayed on his computer and his TNC's state won't be affected
at all by your QSO. In fact, your friend could issue this
connect request,
cmd:CONNECT WB0QRP VIA WA7QST
and you can carry on two separate conversations completely
independently. Monitor the radio transmit indicators and listen
28
Tucson Amateur Packet Radio TNC 2 System Manual
to the speaker audio. See if you can follow the packets and the
acknowledgments back and forth.
Monitoring on the Air
This is a good time to try out the TNC's monitor functions.
While you and your friend are separately connected, type
<CTRL-C>
cmd:MONITOR ON
cmd:MCON ON
cmd:CONVERS
You will be able to see both your "conversation" and your
friend's conversation. Also try HEADERLN ON and MHEARD.
Special Input Characters
The TNC has a number of special characters that can be used to
control its actions. Many of these special characters can be
used to "edit" commands and packet text as they are entered.
These features can all be customized to suit you and your compu-
ter. Most of the special input characters we will describe are
active in both Command Mode and Converse Mode; the exceptions
will be noted.
The character used to return to Command Mode from Converse Mode
is by default a <CTRL-C>. (Sending a BREAK signal also works.)
This character does nothing in Command Mode, so if you
accidentally enter it twice you won't mess up the next command
line. You can change the Command Mode entry character with the
command COMMAND. This is one of several commands that set
special character functions. You can choose any character for
this function, by entering the ASCII character code for the key.
For example, you can use a <CTRL-E> to enter Command Mode by
setting
cmd:COMMAND 5
was $03
The TNC displays the previous value in hex, and you can also
enter character codes in hex if you prefer. All of the special
characters described below can be changed in the same way as
COMMAND.
We have already mentioned that you can erase mis-typed characters
by typing the <BACKSPACE> character. You can change this
character with the command DELETE. If you set DELETE ON, you can
erase characters by typing the <DELETE> character; setting DELETE
29
Tucson Amateur Packet Radio TNC 2 System Manual
OFF returns to using <BACKSPACE>. You will probably want to use
the same key that your computer normally uses to rub out
characters. <BACKSPACE> is more commonly used than <DELETE> by
personal computers. If you aren't sure whether your rubout key
produces <DELETE> or <BACKSPACE> characters, you can try both
settings of the DELETE command and see which works.
When you rub out a mis-typed character, the TNC will attempt to
correct the screen display. This will work for most computers as
well as display-type terminals. It won't work for hardcopy-type
terminals or possibly with a few computers. If your display
doesn't look right after you rub out a character, try setting
BKONDEL OFF. The TNC will not try to correct the display but
will indicate the rubout with a "\" character (<BACKSLASH>). You
can restore display correction by setting BKONDEL ON.
If you make several mistakes in a line, or if you change your
mind, you may want to cancel the whole line rather than rubbing
out the characters one at a time. You can cancel the line by
typing <CTRL-X>. The TNC will display a <BACKSLASH> followed by
<CR>. If you are in Command Mode, you will see a new prompt:
cmd:Hi, John, how are you?<CTRL-X>\
[You started typing text while in Command Mode.]
cmd:CONVERSE
Hi, John, how are you?
The cancel-line character can be changed to any ASCII character
by the command CANLINE.
If you have changed your input by rubbing out and retyping
characters, you may want to see a "fresh" copy of your input,
especially if you have set BKONDEL OFF. The TNC will retype the
line you are entering when you type <CTRL-R>:
cmd:CONNECT KB7\\\WA7<CTRL-R>\
[You mis-typed the call sign.]
cmd:CONNECT WA7GXD
Here the user mis-typed the first three characters of the call
sign and rubbed them out. The TNC displayed "\" for each
character rubbed out. The user then retyped the characters
correctly and redisplayed the line. He finished typing the call
sign on the new line. The redisplay-line character can be
changed to any ASCII character by the command REDISPLA.
If your TNC displays information faster than you can read it
before it scrolls off the screen, you can halt the display by
typing <CTRL-S>. To resume output from the TNC to your computer,
30
Tucson Amateur Packet Radio TNC 2 System Manual
enter <CTRL-Q>. These characters can be changed to any ASCII
character by the commands STOP and START, respectively.
You may occasionally want to include one of the special input
characters in a packet. For example, to send several lines at
once in the same packet, you would have to include <CR> in the
packet at the end of each line, bypassing its "send-packet"
function except at the actual end of the packet. You can include
any character in a packet including all special characters by
prefixing it with the pass character, <CTRL-V>. For example,
I wasn't at the meeting.<CTRL-V><CR>
What happened?
Ordinarily, this message would be sent as two packets. By
prefixing the first <CR> with <CTRL-V>, the operator sends it all
at once, but maintains the <CR> in the text. The pass character
can be changed to any ASCII character by the command PASS.
QRA or help for My path's fallen, and it can't get up
QRA ("Who are you") pinging is supported in release 1.1.8. A
QRA ping polls all of the TNCs within range. Each TNC hearing
the QRA ping will transmit its identification packet within 1 to
16. This technique provides the names of all reachable TNCs and
digipeaters to the new, roving, and emergency-use packeteer.
Also see "ANSWRQRA" command.
Note that the QRA function will not work if there are any
digipeaters in the UNPROTO path. This somewhat, but not com-
pletely, helps limit a malevolent user's ability to seriously
harm the network.
Sending QRA ping:
1) Set the unprotocol callsign to QRA
cmd: UNPROTO QRA<cr>
3) In 1-16 seconds, if MONITOR is ON you should be receiving
packets empty identification packets from other connectable and
compatible TNCs.
WB9FLW>ID:
AD7I>ID:
W5DID>ID:
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Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 5 OPERATION II: FURTHER DETAILS
This chapter describes some aspects of packet operation that you
don't need to be concerned with for everyday conversational
operation. You will want to consult this chapter if you are
using your station for special applications such as a computer
Bulletin Board, binary file transfers, or a "host" program. You
will also find some of this material useful if you intend to
operate on HF or OSCAR, or if your radio has special timing or
other requirements. Even if you don't have any of these applica-
tions, you may enjoy exploring the capabilities of your TNC.
We will use the term "computer" to refer to computers or
terminals. In the command examples, the TNC's prompts and other
messages are shown in ordinary type, your responses are shown in
bold face, and received packets are shown underlined. Commands
and other special keywords are shown in upper case; other text
entered to the TNC is shown in upper and lower case.
Special Characters
The TNC recognizes a number of special characters for input
editing, flow control, and other control functions. You can
change any of these special characters to customize your TNC to
suit your applications, your computer, or your whim. Most of the
characters are set by commands which specify the ASCII character
code for the desired character. You can disable any special
character feature by setting the character value to 0. Input
editing characters may be disabled with no serious effects. You
should use caution in disabling the flow-control or Command Mode
entry characters. Also be careful not to set two special
characters to the same value.
Special characters are normally set to various control char-
acters. Control characters are entered by holding down a special
control key while typing another key. For example, control-C, or
<CTRL-C> is entered by holding down the control key while typing
C. If your computer doesn't have a special control key, you will
have to consult your computer's documentation to see how to enter
these characters. If you will have difficulty entering control
characters, you can change the special characters to, for
example, seldom-used punctuation.
The action of each special character is described in detail under
the entry in Chapter 6 for the command that sets that character.
You can enter the code for a character in either hex (base 16) or
decimal notation. The TNC displays character codes in hex. A
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Tucson Amateur Packet Radio TNC 2 System Manual
number in hex notation is indicated by beginning the number with
a $. The "digits" of a hex number represent multiples of powers
of 16. The values 10 through 15 are represented by the letters A
through F, which may be upper or lower case. For example,
$1B = 1 x 16 + 11 = 27.
Tables of ASCII character codes are available in most computer
manuals. A table of ASCII codes for control characters follows.
The TNC has three operating modes. We discussed two of these
modes, Command Mode and Converse Mode, in Chapter 4. The third
mode, Transparent Mode, is a data-transfer mode like Converse
Mode but is intended primarily for computer data interchange
rather than human conversation. We describe all three of these
modes below. Additionally, the firmware supports the KISS (keep
it simple, stupid) mode. Limited information is supplied here in
the description of the KISS command. A description of this mode
may be found in the proceedings of the Sixth ARRL Computer
Networking Conference. Effective with firmware version 1.1.8,
the TAPR firmware supports a host mode. At the time of this
writing, this was still somewhat experimental and is not
described herein. Contact TAPR for further information.
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Tucson Amateur Packet Radio TNC 2 System Manual
Command Mode
Command Mode is used to enter commands which alter the TNC's
operating parameters. The other modes are entered from Command
Mode. When the TNC is in Command Mode, the Command Mode prompt,
cmd:
is printed at the beginning of each input line. Note, however,
that if the TNC has received and displayed packets, the prompt
may have scrolled off the screen.
The TNC will be in Command Mode after a reset or power-up. After
a power-off, power-on sequence, all operating parameters of the
TNC are re-initialized to the parameter stored in battery
backed-up RAM (bbRAM) by the resident software. After the RESET
command is issued all operating parameters are reset to the
default values stored in EPROM. The values of most parameters
are stored in a permanent but easily changed form in the bbRAM
memory.
The following commands set special characters which are active in
Command Mode. Refer to the discussions of these commands in
Chapter 6 for details on the operation of the characters in
Command Mode. Also see the section on special input characters
in Chapter 4.
CANLINE Cancel current line
CANPAC Cancel output (Command Mode function only)
DELETE Character deletion
PASS Insert following special character
REDISPLA Re-display current line
START, STOP User's flow control characters (sent to TNC)
XOFF, XON TNC flow control characters (sent to
terminal)
The following commands enable display features which are active
in Command Mode. Refer to the discussions of these commands in
Chapter 6 for details on the operation of these characters in
Command Mode. Also see the section on terminal configuration in
Chapter 4.
AUTOLF Add <LF> after <CR> in data sent to terminal
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Tucson Amateur Packet Radio TNC 2 System Manual
BKONDEL Echo after character deletion
ECHO Automatic echo of serial port input
FLOW Type-in flow control
LCOK Lower case translation
NUCR Nulls after <CR>
NULF Nulls after <LF>
NULLS Null count
SCREENLN Automatic <CR> insertion
Entering Data-Transfer Modes
There are several ways to enter a data-transfer mode from Command
Mode. You can type the command CONVERS to enter Converse Mode or
the command TRANS to enter Transparent Mode, and the TNC will
immediately enter the specified mode. The TNC will automatically
enter a data-transfer mode if you are in Command Mode when a
connection is completed. You can specify the data-transfer mode
for automatic entry with the command CONMODE:
cmd:CONMODE TRANS
will specify Transparent Mode, and
cmd:CONMODE CONVERS
will return to the default choice of Converse Mode.
The timing of the automatic entry into data-transfer mode depends
on whether you or the other station initiated the connection.
If you receive a connect request which your TNC accepts, you will
enter data-transfer mode when the TNC sends the connect
acknowledgment (ACK) and types the message *** CONNECTED TO
<callsign>.
If you initiate the connection with the CONNECT command, you can
control the timing of the mode change with the command NEWMODE.
If NEWMODE is OFF, the mode will change when the connect ACK is
received and the *** CONNECTED TO: <callsign> message is typed.
If NEWMODE is ON, you will enter data-transfer mode immediately,
without waiting for a successful connection. Any text sent to
the TNC at this point will be queued up in packets which will
wait for a successful connection before being sent. If the
connect attempt fails, you will be returned to Command Mode. You
will also be returned automatically to Command Mode when either
station disconnects and ends the QSO.
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Tucson Amateur Packet Radio TNC 2 System Manual
Converse Mode
The data mode used most often for ordinary QSOs is Converse Mode.
In Converse Mode, the information you type is assembled by the
TNC into packets and transmitted over the radio. The send-packet
character causes the input to be packetized for transmission. If
you type a full packet-length of characters without typing the
send-packet character, your input will be packetized and
transmitted anyway.
The default send-packet character is <CR>, but you can specify
any character with the command SENDPAC. You may also choose to
have the send-packet character transmitted in the packet or not.
If the send-packet character is <CR> it is natural to include it
in the packet as part of the text as well as interpreting it as a
command. This is accomplished by setting CR ON. If you use some
other character to force packet transmission, you may want to set
CR OFF and inhibit transmission of the send-packet character. If
you set the send-packet character to something other than <CR>,
you can cancel packets of more than one line with the
cancel-packet character, which is set with the command CANPAC.
Single-line packets can be canceled with either the cancel-line
character or the cancel-packet character.
To return to Command Mode from Converse Mode you must type the
Command Mode entry character, or send a BREAK signal over the
serial port. A BREAK is not a regular ASCII character, but it
can frequently be transmitted by typing a special key on the
keyboard.
A BREAK signal is a continuous mark (or 1) signal on the serial
port Transmit Data line lasting approximately 0.2 second. In
fact, the timing of the signal is not very important, and most
serial ports will recognize a BREAK if the mark signal lasts
significantly longer than the time required for a character
transmission. Because of the simple nature of this signal, it is
easily possible to generate a BREAK with circuitry external to
the computer, thus guaranteeing entry to Command Mode in auto-
matic station operation.
The following commands set special characters which are active in
Converse Mode. Refer to the discussions of these commands for
details on the operation of the characters in Converse Mode.
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Tucson Amateur Packet Radio TNC 2 System Manual
CANLINE cancel current line
CANPAC cancel current packet
COMMAND Command Mode entry
DELETE character deletion
MFILTER characters to be filtered in monitored
packets
PASS insert following special character
REDISPLA re-display current line
SENDPAC send current packet
START, STOP user's flow control characters (sent to TNC)
XOFF, XON TNC flow control characters (sent to
terminal)
The following commands enable display features which are active
in Converse Mode. Refer to the discussions of these commands for
details on the operation of these characters in Converse Mode.
8BITCONV Retain high-order bit from serial port
in converse mode
AUTOLF Add <LF> after <CR>
BKONDEL Echo after character deletion
ECHO Automatic echo of serial input
ESCAPE <ESCAPE> translation
FLOW Type-in flow control
LCOK Lower case translation
NUCR Null characters after <CR>
NULF Null characters after <LF>
NULLS Null count
SCREENLN Automatic <CR> insertion
Transparent Mode
Packet radio is very well suited to transfer of data between
computers. In some cases Converse Mode will work well for
computer data transfer. However, files such as a .CMD file on a
CP/M system, a BASIC program, or even a word-processor text file,
may contain characters which conflict with special characters in
Converse Mode. Some of these files may utilize all eight bits of
each byte rather than the seven bits required by ASCII codes. If
you transfer such files you will have to use Transparent Mode.
Transparent Mode is a data-transfer mode like Converse Mode. In
this mode there are no special characters -- everything you type
(or everything your computer sends to the TNC) is sent over the
radio exactly as it was received by the TNC. There are no input
editing features and there is no send-packet character. Packets
are sent at regular time intervals or when a full packet of
information is ready. The time interval at which data is
packetized is set by the PACTIME command.
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Tucson Amateur Packet Radio TNC 2 System Manual
The display characteristics of the TNC are also modified in
Transparent Mode. Data is sent to the computer exactly as it is
received over the radio, including all 8 bits of each byte
received. Features such as auto-linefeed insertion and screen
wrap are disabled, and echoing of input characters is disabled.
The parameters that control these features in Command Mode and
Converse Mode are not changed by entering Transparent Mode, and
all display features are re-enabled when the TNC is returned to
Command Mode. Most of the link status messages that appear as
the TNC moves between disconnected and connected states are also
disabled in Transparent Mode.
In order to permit the Command Mode entry character to be
transmitted freely in Transparent Mode, the escape to Command
Mode from Transparent Mode has been made a little more
complicated. You can still return to Command mode by trans-
mitting a BREAK signal, just as in Converse Mode. You can also
utilize the Command Mode entry character in the following way.
You must wait for a time period after typing the last character
to be sent. This time is set by the command CMDTIME. Following
this wait, you must type three Command Mode entry characters
(default <CTRL-C>) within an interval CMDTIME of each other.
After a final CMDTIME interval in which no characters are typed,
you will see the
cmd:
prompt. If any characters are typed during this interval (even
Command Mode entry characters) the escape will be aborted and all
the Command Mode entry characters that have been typed will be
sent as packet data. If you set CMDTIME to zero you will not be
able to escape from Transparent Mode using this second
procedure.
Flow Control
Whenever data is transferred to computers (home computers or
TNCs), there is a chance that the data will be received faster
than the computer can handle it. Some programs try to deal with
this by providing data buffers for storing incoming data until
the program is ready for it. However, this merely postpones the
problem, since there is a limited amount of room in any buffer.
In order to prevent loss of data the computer must be able to
make whatever is sending data stop sending, and later tell it to
resume sending. If you are a home computer user, you are probably
already familiar with one type of flow control, which allows you
to stop the output from the computer while you read it and
restart it when you are ready for more.
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Tucson Amateur Packet Radio TNC 2 System Manual
The TNC's input buffer may fill up in Command Mode if you try to
type too long a command. In Converse Mode the buffer may fill up
for any of several reasons: you may be using a faster serial
port baud rate than the radio data rate; radio data transmission
may have slowed down because of noise or other users on the
channel; the person or computer at the other end may have stopped
output from that TNC. The TNC will signal the computer to stop
sending data when there is room remaining for about 80 characters
in the buffer. When the buffer fills up entirely, data will be
lost. When the buffer empties so that there is room for at least
270 characters, the TNC will signal the computer to start sending
data again.
A computer file transfer program may be unable to process data
fast enough to keep up with output from the TNC. In order to be
sure of reading every character, a computer must respond to
interrupts from its I/O devices. Some simple programs may poll
the input register for new data. If the polling is not done
often enough, data may be lost. Some computers disable
interrupts during disk accesses. If the program enters a routine
which will not allow it to check for data or respond to it, it
should signal the TNC to stop sending data.
There are two methods of providing flow control which are
supported by the TNC. XON/XOFF flow control, sometimes called
"software flow control," is accomplished by sending a special
character (usually <CTRL-S>) to request that the output stop and
another special character (usually <CTRL-Q>) to restart output.
Hardware flow control may be used if both computers use the Clear
To Send (CTS) and Data Terminal Ready (DTR) lines of the RS-232C
standard.
Some commonly used terminal programs and file transfer programs
for home computers do not implement flow control in software, and
many serial ports do not support hardware flow control. Although
the DTR and CTS lines appear at the connector, they may not be
used on some computers unless the software reads the state of the
CTS line. If you find that the TNC seems to lose data during
file transfers, you should immediately suspect a flow control
problem.
XON/XOFF Flow Control
If you are using a terminal (rather than a computer) or if your
computer does not support DTR/CTS flow control, you should use
XON/XOFF flow control, which is enabled by setting XFLOW ON. The
special flow control characters are set to <CTRL-S> and <CTRL-Q>
by default, but they may be changed. The commands XON and XOFF
set the characters which will be sent to the terminal by the TNC,
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Tucson Amateur Packet Radio TNC 2 System Manual
and the commands START and STOP set the characters to be sent to
the TNC by the terminal. Your computer may receive as many as 4
characters from the TNC after sending a STOP character, since
some characters may already be "in route" through serial I/O
chips.
If you send a STOP (START) character to the TNC when it is
already stopped (started), the character will be ignored. If the
STOP and START character are the same character, this character
will "toggle" the output, turning it off if it is on, and on if
it is off.
You can disable XON/XOFF flow control in one direction only by
setting the appropriate flow control characters to 0. If you do
this, the TNC will automatically use CTS flow control to stop
input from the terminal. XON/XOFF flow control is normally
disabled in Transparent Mode, since all characters are treated as
data. If you cannot use DTR/CTS flow control, you may enable the
XON and XOFF characters (the commands from the TNC to the
terminal) by setting TXFLOW ON and XFLOW ON. The START and STOP
characters (the commands to the TNC from the terminal) can be
enabled in Transparent Mode by setting TRFLOW ON. Note that the
mode is no longer truly transparent when these features are
enabled.
Hardware Flow Control
Hardware flow control is less likely to depend on the programming
of a particular communications program. DTR and CTS are
normally used for flow control signals in Transparent Mode. The
command XFLOW OFF enables hardware flow control in Converse Mode
and Command Mode. Your computer may receive as many as 2
characters after it signals the TNC to stop sending, since some
characters may already be "in route" through serial I/O chips.
Refer to Chapter 7, Hardware for details on the interface
required for hardware flow control.
Type-in Flow Control
Type-in flow control, enabled with the command FLOW, is really a
display feature. It can keep the TNC from interrupting you with
incoming packets when you are in the middle of typing a command
line or an outgoing packet. As soon as you type the first char-
acter of a line, the TNC will put a "hold" on all output (except
for echoing your input). The "hold" remains in effect until you
type a <CR> to end the command line, or a send-packet character
to mark the end of a packet, or until you erase or re-display the
line you have started.
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Tucson Amateur Packet Radio TNC 2 System Manual
Some computers have difficulty simultaneously sending and
receiving characters over the serial port. This is most commonly
the case for computers with "software UARTs." Type-in flow
control will improve the operation of such computers with the
TNC.
Packet Operation
The previous chapter's discussion of "Basic Operation" contains
enough information for most packet operation. This section
describes a few other aspects of packet operation.
Station Identification
Your station identification (call sign) is set with the command
MYCALL, as described in the previous chapter. If you will have
more than one station on the air operating with the same call
sign, they must be distinguished -- no two stations can have
identical station identifications, or the packet protocol will
fail. You can distinguish additional stations by setting the
"secondary station ID", or SSID. This is a number from 0 to 15,
appended to the call sign with a dash:
cmd:MYCALL W3IWI-3
If you don't specify the SSID extension, it will be 0, and the
TNC won't explicitly show SSIDs that are 0. If you want to
connect to a station with a SSID other than 0, or use such a
station as a digipeater, you must specify the SSID:
cmd:CONNECT AD7I-2
or
cmd:CONNECT WA7GXD VIA N7CL-5
The TNC can send an automatic identification packet every 9-1/2
minutes when your station is operating as a digipeater. You can
enable this feature with the command HID ON. An ID packet is
displayed as follows by a monitoring station:
W3IWI-3>ID:W3IWI/R
You can request a final identification as you take your station
off the air with the command ID. The TNC will only send
identification packets if it has been digipeating.
Automatic Operations
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Tucson Amateur Packet Radio TNC 2 System Manual
Normally, any packet station can be used by other stations for
relaying, or digipeating, packets to a more remote destination.
If you don't want your station digipeating packets, you can give
the command DIGIPEAT OFF. Unless there are special
circumstances, such as a station operating on emergency power,
most packet operators set DIGIPEAT ON in the spirit of Amateur
cooperation.
Your station will normally accept a connect request from another
station if it isn't already connected. You can disable this
capability by setting CONOK OFF. If you receive a connect
request when CONOK is OFF, the TNC will display the message
*** connect request: <callsign>
and send a "busy signal" rejection packet to the other station.
If you receive a rejection packet from a station you try to
connect to, your TNC will display
*** <callsign> busy
*** DISCONNECTED
If you want to have a special message sent automatically to
stations connecting to you, you can specify the message with the
command CTEXT. This message can consist of any text string up to
120 characters, and you may include <CR>s by prefixing them with
the pass character:
cmd:CTEXT Sorry, I can't talk right now.<CTRL-V><CR>
I'll be on the air again after 8 PM.<CTRL-V><CR>
Joe
In order for this message to be sent to stations connecting to
you, you must set CONOK ON so that the connection takes place
(default), and enable the automatic message with CMSG ON.
If you want to leave you station on but inhibit transmitting, you
can set XMITOK OFF. If you do this, you would normally set CONOK
OFF as well.
You can have your station periodically send an automatic message
by enabling "beacons." A beacon can be used to make
general-interest announcements, provide packets for other
stations to use to test their ability to receive, or announce the
presence of a bulletin-board operation. The beacon message is
set with the command BTEXT, which works the same way as the CTEXT
command. You enable beacon transmission and set the frequency at
which beacons are sent with the command BEACON. To transmit the
beacon at 10-second intervals, for example, give the command
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Tucson Amateur Packet Radio TNC 2 System Manual
cmd:BEACON EVERY 1
The beacon function also has a transmit-after mode, enabled by
using the keyword AFTER in place of EVERY, in which a beacon
packet is only transmitted after activity is heard on the
channel. This feature might be used to leave an announcement for
other packet users. If someone transmits on an otherwise idle
channel, a beacon can be sent a short time later. No beacons are
sent in this mode if there is a lot of packet activity on the
channel, since the required period of quiet will not occur.
Packet Formatting
The maximum length of a packet is determined by the command
PACLEN. If you type more than the maximum number of characters
without entering a send-packet character, the TNC will transmit a
maximum-length packet. In Transparent Mode, a packet will be
sent if the maximum number of characters is entered before the
delay conditions set by PACTIME force a packet to be sent. Some
TNCs may not be able to accept packets longer than 128
characters.
If you have set the send-packet character to <CR>, you probably
want the <CR> to be included in the packet for display at the
other end. If you set the send-packet character to a special
non-printing character, you probably want the character to be
treated as a command only. The command CR controls whether the
send-packet character is to be echoed and included in the packet.
You can add a <LF> after each <CR> included in your packets by
setting LFADD ON. If the other station reports that lines are
overprinted on his display, and he can't remedy the situation at
his end, you can enable this function.
Commands Affecting Protocol
This section describes some of the commands that affect the
operation of the packet protocol. Details of the protocol are
given in Chapter 9.
The TNC implements AX.25 Level 2 protocol, a set of rules for
formatting messages to other TNCs. The version of AX.25 Level 2
protocol used by the TNC can be set to Version 2.0 with the
command AX25L2V2 ON, or to Version 1.0 with the command AX25L2V2
OFF. Digipeating may not be successful if some TNCs are running
Version 1.0 and some are running Version 2.0. In addition, the
command CHECK controls a timing function that depends on the
protocol version selected.
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Tucson Amateur Packet Radio TNC 2 System Manual
You can specify the "address" to be used for unconnected packets,
as well as intermediate digipeaters with the UNPROTO command.
The format is similar to that of the CONNECT command:
cmd:UNPROTO QST VIA NK6K
The default address for unconnected packets is CQ.
The following functions may be useful for tracking down protocol
problems. They are seldom useful for ordinary packet operations.
The error-checking function of the protocol is disabled for
monitored packets with the command PASSALL. If you set PASSALL
ON, any "packet" will be displayed if it meets the following
conditions: It must start with a flag sequence; and it must
contain an integral number of 8-bit bytes. The TRACE command
enables the display of the address and control fields of packets,
as well as the text. The trace function displays all bytes in
hex as well as ASCII equivalents.
Packet Timing Functions
Transmit Timing
Amateur radio equipment varies greatly in the time delays
required in switching from receive to transmit and from transmit
to receive. If the TNC starts sending data before the
transmitter is operating or before the receiver has had time to
switch from transmitting and lock up on the incoming signal, the
packet will not be received properly. The delay between trans-
mitter keyup and the beginning of data transmission is controlled
by the command TXDELAY. During the time the TNC is keying the
transmitter but not sending data, it will transmit a
synchronizing signal (flags).
If you are transmitting packets through an audio repeater, you
may require a considerably greater keyup delay than is required
for direct communications. Furthermore, the extra keyup delay is
not required if the repeater has not had time to "drop" since the
last transmission. The command AXDELAY allows you to specify an
additional keyup delay to allow the repeater receiver and
transmitter to lock up. The command AXHANG sets the time the TNC
will assume is required for the repeater to drop. If the TNC has
detected channel activity recently enough that the repeater
transmitter should still be on, it will wait only the TXDELAY
time before sending data, rather than adding an AXDELAY time as
well.
The commands TXDELAY, AXDELAY, and AXHANG all set times in units
of 10 ms. If AXDELAY is in effect the total keyup delay will be
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Tucson Amateur Packet Radio TNC 2 System Manual
Keyup delay = (TXDELAY + AXDELAY) * 10
in milliseconds. If channel activity has been heard more
recently than AXHANG*10 ms ago, the keyup delay will only be
Keyup delay = TXDELAY*10
in milliseconds.
Packet Timing
The AX.25 protocol provides for retransmitting packets if no
acknowledgment is heard from the intended destination station
within a certain period of time. A packet might not be
acknowledged due to channel noise or "collision" with another
packet transmission, and since there may be other stations on the
channel, the receiving station may not be able to acknowledge the
received packet immediately. The time lapse before the
originating station retransmits the packet is set by the command
FRACK (frame acknowledge time). The maximum number of
retransmissions before the originating station terminates the
connection is set by the command RETRY. The maximum number of
transmissions of a packet is RETRY+1, since the initial
transmission does not count as a retransmission. Setting RETRY
to 0 specifies an infinite number of retries.
The frame-acknowledge time is automatically corrected for the
additional time required for digipeating. The time in-terval
before TNC 2 retransmits an unacknowledged packet is
Retry interval = FRACK * (2*n + 1)
in seconds, where n is the number of digipeaters in use for this
connection.
Acknowledgments of digipeated packets are made from end to end,
and digipeaters do not acknowledge the packets they relay. If
there are several intermediate relays, the chance of either the
original packet or the acknowledgment to be lost increases dras-
tically. To reduce this problem, an automatic wait time can be
imposed on any station not transmitting a digipeated packet.
Stations waiting for a clear channel to transmit packets wait for
this time interval after the channel clears before transmitting.
This wait does not apply if the station will be transmitting one
or more digipeated packets. This usually gives the digipeater a
clear chance at the channel.
The wait time is set by the command DWAIT, which specifies 40 ms
intervals. If no digipeating is being done by anyone in the
local area, this parameter can be set to 0, but in any event it
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Tucson Amateur Packet Radio TNC 2 System Manual
should be set to the same value by all members of a local packet
group.
In order to avoid unnecessary packet retries, the TNC implements
a collision-avoidance strategy which applies to all packets
except those being digipeated. On the second and subsequent
transmissions of a particular packet, the TNC waits an additional
random time after detecting a clear channel before beginning
transmission. This prevents repeated collisions of transmissions
by the same two stations. The random time is a multiple (0-15)
of the TXDELAY time.
The interval, in milliseconds, between the TNC detecting
carrier-drop and beginning to transmit is
Wait time = DWAIT * 10
for the first transmission of a packet. For subsequent
transmissions of the same packet the interval is
Wait time = DWAIT * 10 + ( r * TXDELAY ) * 10
where r is a random number from 0 to 15. Thus, if your TNC is
forced to re-transmit packets, you will occasionally hear a
fairly long delay before transmission begins.
Multiple packets may be transmitted before waiting for an
acknowledgment. This permits more efficient channel use when
large amounts of data are being transferred. The maximum number
of packets which the TNC will send before waiting for
acknowledgment is specified by the command MAXFRAME. This does
not mean that the TNC will wait until several packets have been
entered before transmitting. MAXFRAME in combination with the
command PACLEN, which sets the maximum number of characters in a
packet, determines how much information can be sent in a single
transmission. The best combination for efficient data transfer
is determined partly by the channel quality and partly by the
rate at which the terminal can process data. For a 1200 baud
terminal data rate, you should start with a combination that
produces about 300 characters outstanding at one time.
Radio Baud Rate
The radio data transmission rate is set by switches 6, 7 and 8 of
DIP switch SW2 (Do not change these switches while power is on,
and make sure only one of these three switches is ON at any time
while the TNC is powered). The rates available are:
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Tucson Amateur Packet Radio TNC 2 System Manual
Table 5-2. DIP switch settings for
radio baud rates.
Radio Data Rate SW2 Switch Setting
(baud) 6 7 8
300 ON OFF OFF
1200 OFF ON OFF
9600 OFF OFF ON
Note that there is no relationship between terminal baud rate and
radio baud rate. In order to communicate with another packet
station you must use the same radio baud rates. The length of
time required to send a given amount of information increases as
the baud rate decreases. For example, it takes four times as
long to send data at 300 baud as at 1200 baud. If you use slow
radio baud rates, you should limit the length of transmissions by
setting MAXFRAME to 1 and choosing PACLEN so that the hardware
watchdog timer does not disrupt your transmissions and channel
traffic is broken up frequently.
The Bell-202 compatible modem is optimized for a 1200 baud radio
data rate. For HF operation at low baud rates, you should
reconfigure the modem as described in Chapter 7. The on-board
modem is not useful at rates higher than 1200 baud. The TNC can
provide data signals at 9600 baud, but an external modem is
required for such operation.
Special Protocol Times
You can set up a connection timeout with the command CHECK, which
specifies a time in multiples of 10-second intervals. This
function prevents your TNC from getting stuck in a connection
when the other station disappears for longer than the specified
time. The TNC uses this time somewhat differently depending on
the setting of AX25L2V2.
The command RESPTIME sets a delay between the receipt of a packet
and the transmission of the acknowledgment packet. This delay is
used to prevent collision between an acknowledgment and another
packet from the sending station. This is primarily necessary
during file transfers; otherwise the delay is best set to 0.
During file transfers the stations receiving the file should set
RESPTIME to 10 or 12 (default).
The timing of packet transmission in Transparent Mode is
determined by the command PACTIME. You can choose the way packet
transmission is timed. If you are typing input to a remote
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Tucson Amateur Packet Radio TNC 2 System Manual
computer it is usually best to have packets transmitted at
regular intervals. If your computer is operating a remote-host
or bulletin board program you should send packets after an
interval with no further input from the computer. You can enable
the use of PACTIME in Converse Mode with the command CPACTIME.
Monitor Functions
The TNC's protocol is designed for setting up "circuits" between
two stations. However it can also operate in a mode more
suitable for a "net" or "round-table" discussion with several
participants, although reliable reception of all transmissions by
every station cannot be guaranteed. This is done by enabling the
monitor functions. Most of the monitor functions are described
in Chapter 4.
Monitoring is enabled by the command MONITOR ON, and separate
monitor functions are individually enabled.
If connected packet QSOs are taking place on the frequency of
your group conversation, you may wish to ignore all connected
packets while your group operates in unconnected mode. The
command MALL OFF causes the TNC to ignore connected packets.
If you want to be able to monitor packet activity when your
station is not connected, but have all monitoring automatically
cease when you connect to someone, set MCON OFF.
If you want to monitor stations selectively, you can set up a
list of up to eight callsigns with the command LCALLS. The
callsigns in this list are regarded as "buddies," i.e., the only
stations you want to listen to if BUDLIST is ON. Otherwise, the
stations in the list will be ignored, and all other stations will
be monitored.
You can operate a group conversation with some data integrity by
having the stations connect in pairs and setting MALL ON and MCON
ON. This does not insure that every packet is received at every
station, but it does insure that a packet involved in a collision
will be retried. If you have an odd number of stations
participating in this sort of conversation, one station can
connect to himself via another station as digipeater.
For example, WB6YMH, WD0ETZ, WA0TTW, W1BEL, and K9NG wish to
carry on a group conversation. In order to make all the
transmissions as reliable as possible, the following connections
are made.
WB6YMH connects to W1BEL
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Tucson Amateur Packet Radio TNC 2 System Manual
WA0TTW connects to K9NG
WD0ETZ connects to WD0ETZ via W1BEL
If each station specifies MCON ON and MALL ON, each station will
see the packets sent by all the others.
Ordinarily, only text packets are displayed. If you want to see
some of the protocol packets, you can set MCOM ON and connect,
disconnect, disconnect acknowledgments, and DM (connect-request
rejection) packets will be displayed. For example,
WB9FLW>N7CL <C>
KV7B>N2WX <D>
indicate connect and disconnect packets. Disconnect ac-
knowledgments are designated <UA>, and DM packets are <DM>.
You can cause the TNC to "filter" certain characters from
monitored packets with the command MFILTER. This allows you to
remove, for example, form-feeds, bell characters, or extra <LF>s
that may be necessary to the stations involved in a connection,
but which may interfere with your display. You can specify up to
four characters by giving the ASCII character codes in hex or
decimal.
Real-Time Clock and Time Stamping
You can enable the TNC's real-time clock by setting the date and
time with the command DAYTIME. Once you have set the clock, you
can request the time by entering DAYTIME with no parameters. The
format of date and time display is controlled by the command
DAYUSA. If the TNC is powered off, DAYTIME will have to be
reset.
Monitored packets can be time-stamped if DAYTIME has been set.
To enable this function, set MSTAMP ON. You can also time-stamp
connect and disconnect messages with the command CONSTAMP ON.
HF and OSCAR
The TAPR TNC 2 is optimized for a local VHF FM environment: The
modem is configured for best response at 1200 baud. The settings
of MAXFRAME and PACLEN provide the possibility of several con-
tinuous frames of long data length.
The requirements for optimum performance with a typical HF or
OSCAR 10 path are very different. Lower signal to noise ratios
require lower baud rates, noise spikes and fades require shorter
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Tucson Amateur Packet Radio TNC 2 System Manual
packet lengths, and a higher rate of false carrier detects lowers
the total usable dynamic range in the audio input. The TNC
hardware and software can be reconfigured to improve throughput
in these environments. For HF operation at 300 baud, we
recommend setting MAXFRAME to 1.
The TNC detects a busy channel by monitoring the lock-detect
signal from the demodulator. The presence of a lock-detect
signal is indicated by the Data Carrier Detect (DCD) LED. Each
time DCD goes off the TNC will start a DWAIT interval which must
elapse before the channel is considered to be available. On a
noisy channel spurious lock-detect signals may be generated. For
HF and OSCAR operation you should set DWAIT to 0. The random
wait before retry transmissions can be disabled by setting
TXDELAY 0 and using AXDELAY to set the required keyup delay. Of
course, AXHANG should be 0 for this application.
If you are operating a full-duplex radio station (simultaneous
transmit and receive) such as an OSCAR 10 station, you should set
FULLDUP ON. The TNC is always electrically capable of full
duplex operation, but this parameter causes the protocol to
behave differently in acknowledging packets. In addition, the
TNC will ignore the state of the DCD line. You may be able to
improve operation somewhat by disconnecting the DCD line at the
modem connector (J4 pins 1-2).
Although intuition tells you that lower baud rates will reduce
the number of packet retries, there is usually a small range
between "too fast" and "too slow." A slower packet takes longer
to transmit and is therefore a larger target for fades and static
crashes. The entire packet must be received correctly in order
to be accepted. Data rates of 1200 baud have been used on both
HF and through OSCAR 10.
You can improve the response of the modem for low baud rates by
calibrating the modulator and demodulator tones for a narrow
shift, as described in the next section, and modifying the
demodulator. This also permits the use of a narrow filter by the
receiving station. You should set the demodulator center
frequency so that it is midway between the high and low tones
when the packet tones are centered in your passband. The modem
parameters and timing constants are determined by the parts on
headers U15 and U19. Consult the EXAR notes listed in the
Bibliography for the procedure for determining component values.
If you are dedicating your TNC to 300 baud operation, consider
increasing the time-constant of the filter at U20 pin 3 by a
factor of 4 (increase the capacitor value, not the resistor).
The on-board modem can be completely bypassed at connector J4.
You can supply an external modem which uses other modulation
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Tucson Amateur Packet Radio TNC 2 System Manual
methods or higher baud rates. The interfaces available on J4 are
TTL levels. Refer to Chapter 7 for more information.
Modem Calibration using CAL and RXCAL
The TAPR TNC 2 contains a versatile, user configurable FSK modem
that is suitable for both 1200 baud packet use as well as lower
data rate use, such as 200 Hz shift 300 baud use on HF links.
Calibration of the modem is usually only required when the unit
is initially put into operation or when you want to change the
modem characteristics. You may want to check the calibration if
you have difficulty connecting to other packet stations, but
recalibration is normally not necessary.
Calibration of the TNC on-board modem is straightforward. First,
determine the data rate at which you wish to operate. The
required shift may then be determined, followed by the actual FSK
frequencies to use. While you may select from any tones in the
normal audio range, there are a few simple rules that may help.
1. The TNC only supports 300 baud and 1200 baud operation of the
radio link using the on-board modem. While the modem is capable
of operating at other data rates, the TNC data-rate generator
circuit only supplies clocks for 300, 1200 and 9600 baud (9600
baud is for use with an external modem).
2. Most 1200 baud operation uses 1000 Hz shift and tones of 1200
Hz and 2200 Hz. These are the default tones for which the TNC
modem is optimized, using the components supplied in the kit.
However, 800 Hz shift with tones of 1300 Hz and 2100 Hz may
provide improved operation. This tone-pair is compatible with
TNCs using 1000 Hz shift modems.
3. Most HF operation below 28 MHz uses 300 baud, 200 Hz shift
FSK. TAPR recommends 1600 Hz and 1800 Hz as the modulator tone
frequencies, but any pair of frequencies with this separation,
modulating an SSB transmitter, will work. If your demodulation
center frequency is 1700 Hz, your transmissions will be readable
whenever you are able to copy the other station, regardless of
his actual modulation frequencies. Incidentally, the sideband
may be chosen at will due to the nature of the data, although
most stations conventionally use LSB.
In the example below we will set up the modem for normal 1200
baud operation with 800 Hz shift.
The software calibration routine compares the frequency being
calibrated against a reference signal. The desired frequency is
specified by setting a count, n, using the command CALSET.
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Tucson Amateur Packet Radio TNC 2 System Manual
For the modulator, determine the calibration count according to
the following formula:
n = (525,000 / f) + 1
where f is the desired frequency in Hertz. Substituting 1300 and
2100 Hz, we end up with:
n = 405 (for 1300 Hz)
n = 251 (for 2100 Hz)
To set the PLL demodulator, we use the RXCAL command, explained
below.
Modulator Adjustment
The next step is to preset the trimpots for the modulator. When
adjusting the trimpots, you should hear a soft "click" when the
element is adjusted to the end of its travel. Turning the
element past this point will not result in damage to the trimpot;
however, it is suggested that you do not make a practice of
turning the adjustment screw past this point too much. Use a
small-tipped screwdriver or special trimpot adjusting tool when
adjusting the trimpots.
Preset R77 20 turns counter-clockwise (CCW) or until you hear the
element "click" at full CCW rotation. R77 controls the higher of
the two modulator output tones and this sets it to its maximum
frequency.
Preset R78 20 turns clockwise (CW) or until you hear the element
"click" at full CW rotation. R78 controls the lower of the two
modulator output tones and this sets it to its lowest frequency.
Turn off the power to the TNC and remove it from its cabinet. To
protect the battery backed-up RAM, be sure to set the TNC on a
non-conducting surface -- a sheet of paper will do. Attach your
terminal and follow the standard power-up procedure. When you
see the command mode prompt, enter
cmd:CALSET 405
or use the value appropriate for the lower modulator tone. Next,
enter
cmd:CALIBRA
This starts the software calibration routine. The "commands" to
the calibration routine are single characters, and require no
carriage return.
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Tucson Amateur Packet Radio TNC 2 System Manual
Install a push-on jumper at JMP9 pins 1 and 6 (the top two pins
of JMP9 nearest C44) and another push-on jumper at JMP4.
NOTE: During calibration the STA and CON LEDs are used as
frequency indicators. When the STA LED is glowing, the frequency
is too high, go lower. When the CON LED is glowing, the
frequency is too low, go higher.
Press the K key on your computer. Either the STA or CON LED
should illuminate. Next, press the space bar on your keyboard
and verify that the other LED (CON or STA) illuminates in place
of the one illuminated in the preceding step. Press the space
bar again until the CON LED is illuminated.
Slowly rotate the adjustment screw on trimpot R78 in the CCW
direction until both the STA and CON LEDs illuminate. The LEDs
are a bit slow to respond, so be careful when the STA LED begins
to flicker. You will probably notice a portion of the adjustment
when both LEDs illuminate; set the adjustment screw to the center
of this band. If you go too far, only the STA LED will be
illuminated; in this case, turn the adjustment screw CW.
When both LEDs are steadily illuminated, press the Q key. Both
LEDs should extinguish and the command mode prompt should
reappear. The lower tone is now calibrated.
To calibrate the upper tone, enter
cmd:CALSET 251
or use the value appropriate for the higher modulator tone.
Next, enter
cmd:CALIBRA
Now press the K key. Either the CON or the STA LED should
illuminate. Tap the space bar until the STA LED glows.
Slowly rotate the adjustment screw of trimpot R77 CW, following
the instructions above for setting R78. Continue the adjustment
until both the STA and CON LEDs glow steadily.
When both LEDs are steadily illuminated, press the Q key. Both
LEDs should extinguish and the command mode prompt should
reappear. Remove the jumpers at JMP9 pins 1 & 6 and at JMP4.
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Tucson Amateur Packet Radio TNC 2 System Manual
Demodulator Adjustment
NOTE: Do not remove the jumper at JMP8 for demodulator
calibration!
To calibrate the PLL demodulator, preset R79 20 turns clockwise
(CW) or until you hear the element "click" at full CW rotation.
Place a jumper across JMP9 pins 3 and 4 (the lowest two pins --
these are the two pins nearest the silkscreen legend "C43").
Install a push-on jumper at JMP4 (to disable the transmitter PTT
watchdog timer) and another at JMP7 (to establish "analog
loopback"). Enter
cmd:RXCAL
at the computer or terminal keyboard.
Now press the K key. The STA LED should illuminate.
Slowly rotate the adjustment screw of R79 CCW until both the STA
and CON LEDs glow. This is a very difficult condition to
achieve, partly because the indicator is quite sensitive and
partly because the LEDs lag the adjustment by a second or two.
However, if you establish the position of the trimpot where the
LEDs toggle and leave R79 set to within about 1/4 turn of that
position there will be no degradtion in performance.
Type Q and note that the command mode prompt reappears. Remove
the jumpers at JMP4, JMP7 and JMP9. Your TNC 2 modem is now
calibrated to the tones you have selected.
Other Considerations
If you are operating at a data rate other than 1200 baud, the
loop timing components on your demodulator will not be optimum.
The table below lists the component values for the two most
common FSK pairs as well as CALSET parameters.
NOTE: Components used for R93 and C54 should have tem-
perature-stable characteristics.
Finally, it is best to match the IF bandwidth of your receiver to
the data rate you will operate. For 300 baud HF operation, a
filter of about 500 Hz bandwidth is optimum; any CW filter wider
than this should be better than an SSB bandwidth filter!
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Tucson Amateur Packet Radio TNC 2 System Manual
Chapter 6 TAPR TNC 2 COMMANDS
This chapter serves as a complete reference to all TNC commands.
Commands are used to control the many variable values which
affect your TNC's operation, as well as causing it to perform
specific actions, such as connecting to another station to start
a QSO. You can enter a command to your TNC whenever you see the
command-mode prompt:
cmd:
You will change parameters and issue instructions to the TNC by
typing commands composed of English-like words or word
abbreviations, which are called keywords, and variables which are
numbers or strings of characters chosen by the user. You will
probably never change some of these parameters; however, one of
TAPR's goals is to allow each user maximum flexibility to adapt
the TNC to his environment.
Entering Commands
You may use either upper case (capital letters) or lower case
(small letters) when you enter commands. In order to have your
TNC accept a command line, you must finish the line with a <CR>,
or carriage return character. This won't be mentioned explicitly
in the examples below. Before you type the final <CR> of your
command, you can correct typing mistakes or cancel the line
completely. See Chapter 4 for a discussion of input line
editing.
This chapter will use UPPER CASE for commands and lower case for
explanatory text. In examples showing input typed by the user
together with the responses of the TNC, the user's input will be
shown in bold face.
Whenever the TNC accepts a command which changes a value, it will
display the previous value. For example, if you type
XFLOW OFF
you might see the display
XFLOW was ON
This reminds you of what you have done, and indicates that the
value has been successfully changed.
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Tucson Amateur Packet Radio TNC 2 System Manual
If you type something your TNC can't understand you will get an
error message. If you type an unrecognized command, you will see
the message ?EH. If you get a command name correct, but the
arguments are wrong, you will see the message ?BAD. A complete
list of error messages appears at the end of this chapter. For
example,
cmd:ASDFASDF || This isn't a command.
?EH
cmd:BEACON E || A parameter was left out.
?BAD
Command List
The commands are listed alphabetically, and each command entry
contains several sections, as follows.
COMMAND NAME
The boldface command name at the top of the entry is the word you
will type in order to have your TNC execute this command. The
command name is printed with some letters underlined. These let-
ters form the minimum abbreviation that you may use and still
have your TNC understand your command. Of course, you may type
out the entire command word, or any abbreviation longer than the
minimum abbreviation, if you like.
For example, the command MYCALL may be specified by simply typing
MY. The abbreviation M is not sufficient (and will be
interpreted as a different command), but MY, MYC, MYCA, MYCAL or
MYCALL are all acceptable.
If the command requires parameters, they will be indicated after
the command name.
Default
For commands that set values, your TNC assumes a "most often
used" or default condition. The defaults are the values stored
in EPROM which are loaded into RAM when the system is first
powered up, or when you give the RESET command. Immediate
commands perform actions rather than setting values, and don't
have defaults.
Parameters
There are several types of parameters. Some parameters can have
one of only two values, such as ON and OFF or EVERY and AFTER.
If a parameter must be one of two values, the choices are shown
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Tucson Amateur Packet Radio TNC 2 System Manual
separated by a vertical bar. You may use YES instead of ON and
NO instead of OFF.
A parameter designated as n is a numeric value. These values may
be entered as ordinary decimal numbers, or as hexadecimal, or
"hex", numbers by preceding the number with a $ symbol. When
the TNC shows some of these numeric parameters (those which set
special characters), they will be given in hex. The "digits" of
a hex number represent powers of 16, analogous to the powers of
10 represented by a decimal number. The numbers 10 through 15
are denoted by the hex digits A through F. For example,
A parameter designated as text, such as the argument to CTEXT,
may be entered in upper or lower case, and may include numbers,
spaces, and punctuation. The text is accepted exactly as typed
by the user.
Several commands require callsigns as parameters. While these
parameters are normally Amateur call signs, they may actually be
any collection of numbers and at least one letter up to six
characters; they are used to identify stations sending and
receiving packets. A callsign may additionally include
sub-station ID (SSID), which is a decimal number from 0 to 15
used to distinguish two or more stations on the air with the same
Amateur call (such as a base station and a repeater). The call
sign and SSID are entered and displayed as call-n, e.g., K0PFX-3.
If the SSID is not entered, it is set to 0, and SSIDs of 0 are
not displayed by the TNC.
Some commands have parameters which are actually lists of items.
For example, you may specify as many as eight callsigns to be
selectively monitored with the command LCALLS. The second and
later items in the list are optional, and you may separate the
list items with blank spaces or with commas.
BEACON EVERY|AFTER n
means that the command BEACON requires an argument which must be
either EVERY or AFTER (abbreviated to E or A), and an argument n
which the user may choose from a range of values. An acceptable
command might be BEACON E 2.
CONNECT call1 [VIA call2[,call3...,call9]]
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Tucson Amateur Packet Radio TNC 2 System Manual
means that the command CONNECT requires a callsign argument
call1. You may optionally include the keyword VIA, followed by a
list of one to eight callsigns, call2 through call9. The
callsigns in the list, if included, must be separated by commas
(as shown), or by blank spaces. An acceptable command might be C
N2WX V AD7I WB9FLW.
You can see the current value of the command's arguments by
typing the command name by itself, without any arguments. For
example,
cmd:CONOK Y || Sets the value to YES (ON).
CONOK was OFF || Displays previous value.
cmd:CONOK || Command with no arguments
CONOK ON || Displays present value.
A special command, DISPLAY, allows you to see the values of all
parameters or groups of related parameters.
Remarks
This section describes the command's action and the meaning of
each argument. Examples may be included of situations in which
the command might be used.
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Tucson Amateur Packet Radio TNC 2 System Manual
8BITCONV ON|OFF Default: OFF
Display Group: A
Parameters:
ON The high-order bit is not stripped in Converse Mode.
OFF The high-order bit is stripped in Converse Mode.
This command enables transmission of 8-bit data in Converse Mode.
If 8BITCONV is OFF, the high-order bit (bit 7) of characters
received from the terminal is removed before the characters are
transmitted in a packet. The standard ASCII character set
requires only 7 bits, and the final bit is used as a parity bit
or ignored. Setting bit 7 in text characters transmitted over
the air may cause confusion at the other end.
If you need to transmit 8-bit data, but don't want all the
features of Transparent Mode, you should set 8BITCONV ON and
AWLEN 8. This may be desirable, for example, if you are using a
special non-ASCII character set.
Bit 7 is always removed in Command Mode, since commands require
only the standard 7-bit ASCII character set.
ACKPRIOR ON|OFF Default: ON
Display Group: L
Parameters:
ON Enables Prioritized acknowledgments.
OFF Acknowledgments have the same priority as any other
frames on the channel.
When ACKPRIOR is ON, acknowledgments have priority. This means
that is your TNC receives a frame that it must acknowledge (ACK),
it will immediately send the ACK if the channel is clear. If
other stations are running with ACKPRIOR ON, they will not access
the channel until you have had a chance to send the ACK, even if
they cannot hear your transmissions.
When OFF, acknowledgments are queued up for transmission the same
as any other frame.
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Tucson Amateur Packet Radio TNC 2 System Manual
ACKTIME n Default: 14
Display Group: T
Parameters:
n 0-250 in 10 mSec increments.
ACKTIME specifies the time required to send an RR or RNR response
frame (an acknowledgment) to an I frame at the radio port data
rate. This corresponds to about 510 mSec at 1200 bps with 8
digipeaters and about 140 mSec at 1200 bps with no digipeaters.
The default of 140 mSec (ACKT 14) allows for no digipeaters.
ANSWRQRA ON|OFF Default: ON
Setting ANSWRQRA to OFF disables the TNC's ping-response func-
tion. When the parameter is set ON, the TNC responds to non-
digipeated UI frames addressed to QRA, within 1 to 16 seconds,
with an empty ID packet. TNC-2 ignores QRA packets when ANSWRQRA
is off.
AUTOLF ON|OFF Default: ON
Display Group: A
Parameters:
ON A linefeed character (<LF>) is sent to the terminal
after each carriage return character (<CR>).
OFF A <LF> is not sent to the terminal after each <CR>.
AUTOLF controls the display of carriage return characters
received in packets as well as echoing those that are typed in.
If the TNC's sign-on message lines appear to be typed over each
other, you should set AUTOLF ON. If the TNC's sign-on message
appears to be double-spaced, you should set AUTOLF OFF. If the
TNC's sign-on message appears to be single-spaced, you have
AUTOLF set correctly.
This command only affects what is displayed, not the data sent in
packets. If you want to add linefeed characters to outgoing
packets, use the command LFADD.
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Tucson Amateur Packet Radio TNC 2 System Manual
AWLEN n Default: 7
Display Group: A
Parameters:
n 7 - 8, specifying the number of data bits per
word.
This value defines the word length used by the serial IO terminal
port.
For most packet operations, including conversation, bulletin
board operation, and transmission of ASCII files, you should set
AWLEN 7. If 8 bit words are transmitted to the TNC in Command
Mode or Converse Mode, the eighth bit is normally removed,
leaving a standard ASCII character, regardless of the setting of
AWLEN.
To transmit and receive packets retaining all 8 data bits of each
character, as you need to do if you send executable files or
other special data, you should use Transparent Mode and set AWLEN
8. Alternatively, you can use Converse Mode and set AWLEN 8 and
8BITCONV ON (however, the data you then send must handle the
Converse Mode special characters with the PASS prefix).
AX25L2V2 ON|OFF Default: ON
Display Group: L
Parameters:
ON The TNC will use AX.25 Level 2 Version 2.0 protocol.
OFF The TNC will use AX.25 Level 2 Version 1.0 protocol.
Some implementations of the earlier version of AX.25 protocol
(e.g., TAPR's TNC 1 running TAPR 3.x firmware) won't properly
digipeat version 2.0 AX.25 packets. This command exists to
provide compatibility with these other TNCs until their software
has been updated.
In addition, some HF packet operators prefer AX.25 Version 1.0
protocol due to its reduced overhead during retries.
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Tucson Amateur Packet Radio TNC 2 System Manual
AXDELAY n Default: 0
Display Group: T
Parameters:
n 0 - 180, specifying the voice repeater keyup delay
in 10 ms intervals.
AXDELAY specifies a period of time the TNC is to wait, in
addition to the normal delay set by TXDELAY, after keying the
transmitter and before data is sent. This feature will be used
by groups using a standard "voice" repeater to extend the range
of the local area network. Repeaters with slow mechanical
relays, split sites, or other circuits which delay transmission
for some time after the RF carrier is present require some amount
of time to get RF on the air.
If you are using a repeater that hasn't been used for packet
operations before, you will have to experiment to find the best
value for n. If other packet stations have been using the
repeater, check with them for the proper setting. This command
acts in conjunction with AXHANG.
Note that the TAPR TNC 1 and other TNCs using the same version
3.x firmware interpret n in 120 ms intervals. The value set by
AXDELAY on TNC 2 will thus be 12 times the value used by a TNC 1
user to give the same delay time.
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Tucson Amateur Packet Radio TNC 2 System Manual
AXHANG n Default: 0
Display Group: T
Parameters:
n 0 - 20, specifying the voice repeater hang time in
100 ms intervals.
This value can be used to increase channel efficiency when an
audio repeater with a hang time greater than 100 ms is used. For
a repeater with a long hang time, it is not necessary to wait for
the repeater keyup delay after keying the transmitter if the
repeater is still transmitting. If the TNC has heard a packet
sent within the hang period, it will not add the repeater keyup
delay (AXDELAY) to the keyup time.
If you are using a repeater that hasn't been used for packet
operations before, you will have to experiment to find the best
value for n. If other packet stations have been using the
repeater, check with them for the proper setting.
Note that the TAPR TNC 1 and other TNCs using the same version
3.x firmware interpret n in 120 ms intervals. The value you set
on TNC 2 for AXHANG will thus be 6/5 the value used by a TNC 1
user for the same hang time (when converting, round down to the
nearest integer).
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Tucson Amateur Packet Radio TNC 2 System Manual
BBSMSGS ON|OFF Default: OFF
Display Group: A
This command controls how the TNC displays certain messages in
COMMAND and CONVERSE modes. The messages affected are described
below:
*** Connect request: xxxx - This message is omitted
The BBSMSGS command is primarily useful for host operation, such
as with W0RLI and similar bulletin board systems that require
link status messages to begin in the first output column.
The connect request message is omitted during BBSMSGS mode. This
should be most useful for preventing corruption of messages when
forwarding with small frames.
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BEACON EVERY|AFTER n Default: EVERY 0
Display Group: I
Parameters:
EVERY Send beacon at regular intervals.
AFTER Send beacon once after the specified time interval
with no packet activity.
n 0 - 250, specifying beacon timing in 10 second
intervals. A value of 0 disables the beacon.
This command enables beacon sending and causes the first beacon
frame to be transmitted. A beacon frame consists of the text
specified by BTEXT in a packet addressed to "BEACON" and sent via
the digipeat addresses specified by the UNPROTO command, if any.
If the keyword EVERY is specified, a beacon packet is sent every
n*10 seconds. This mode might be used to transmit packets for
testing purposes.
If AFTER is specified, a beacon is sent only after n*10 seconds
have passed with no packet activity. In this case, the beacon is
sent only once until further activity is detected. This mode can
be used to send announcements or test messages only when packet
stations are on the air. If you choose n properly you can avoid
cluttering a busy channel with unnecessary transmissions.
Beacon frames from other TNCs can be monitored by setting MONITOR
ON.
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BKONDEL ON|OFF Default: ON
Display Group: C
Parameters:
ON The sequence <BACKSPACE> <SPACE> <BACKSPACE> is echoed
when a character is deleted from the input line.
OFF The <BACKSLASH> character (\) is echoed when a
character is deleted.
This command determines the way the display is updated to reflect
a character deletion in Command Mode or Converse Mode.
The <BACKSPACE> <SPACE> <BACKSPACE> sequence will properly update
the screen of a video display. If you have a video display
terminal or computer, you should set BKONDEL ON.
The <BACKSPACE> <SPACE> <BACKSPACE> sequence on a printing
terminal would result in overtyped text. If you have a
paper-output display, or if your terminal does not respond to the
<BACKSPACE> character (<CTRL-H>), you should set BKONDEL OFF.
The TNC will type a <BACKSLASH> for each character you delete.
You can display the corrected input line by typing the
redisplay-line character, which is set by the command REDISPLA.
NOTE: BKONDEL is only active in COMMAND and CONVERSE modes.
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BTEXT text Default: ""
Display Group: I
Parameters:
text Any combination of characters and spaces, up to a
maximum length of 120 characters.
BTEXT specifies the content of the data portion of a beacon
packet. The default text is an empty string, i.e., no message.
Beacon packets are discussed in more detail under the BEACON
command.
You can send multiple-line messages in your beacon by including
carriage return (<CR>) characters in the text. The <CR>
character can be included by preceding it with the pass charac-
ter. The pass character is set by the PASS command. If you
enter a text string longer than 120 characters, an error message
will appear and the command will be ignored.
For example, a Bulletin Board program might set the beacon text
to a message like this, updating the text after each connection:
Mailbox on line. Messages for WB9FLW, AD7I, K9NG.
To clear the BTEXT text without issuing the RESET command, use a
% or & character as the first character in the text.
The BTEXT text is stored in battery-backed RAM.
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BUDLIST ON|OFF Default: OFF
Display Group: M
Parameters:
ON Ignore frames from stations which are not in the LCALLS
list.
OFF Ignore frame from stations which are in the LCALLS
list.
BUDLIST works in conjunction with the command LCALLS, which sets
up a callsign list. These commands determine which packets will
be displayed when you have set MONITOR ON. BUDLIST specifies
whether the callsigns in the list are the ones you want to ignore
or, alternatively, are the only ones you want to listen to.
If you want to listen only for packets from a limited list, you
should enter this list with LCALLS and set BUDLIST ON. You can
use this feature, for example, to have your TNC "keep an ear out"
for a particular station while you converse with someone else.
If you want to ignore packets from a limited list, you should
list the callsigns to ignore in LCALLS and set BUDLIST OFF. For
example, if there is a bulletin board on frequency, you can
ignore it while monitoring other conversations.
CALIBRA
Display Group: NONE
CALIBRA is an immediate command, and is used to transfer control
to the modem calibration routine. Calibration may be performed
at any time without altering the current link state.
Briefly, the commands available in the calibration routine are:
<SPACE> Switch the transmit audio to the other tone.
D Alternate between the two transmit tones at a
rate determined by the radio port data rate.
K Toggle PTT line on/off.
Q Quit calibration routine.
Calibration of the modem tones is described in the modem
calibration section of Chapter 5. Adjustment of the tone levels
using CALIBRA is described in Chapter 3. See also RXCAL.
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CALSET n Default: None
Display Group: T
Parameters:
n 0 - 65535, specifying the count setting for use by
the calibration routine.
The number to be specified by CALSET is determined by the
frequency f to be calibrated as follows.
n = (525,000 / f) + 1 (modulator tones)
n = (262,500 / f) + 1 (demodulator tones)
Round n to the nearest integer. To calibrate the modem tones,
you will set n for the desired frequency using CALSET, enter the
calibration routine with CALIBRA, and adjust the tone following
the instructions in Chapter 5. To calibrate the next tone, exit
the calibration routine and set n for the next frequency.
See also RXCAL.
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CANLINE n Default: $18 <CTRL-X>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command is used to change the cancel-line input editing
command character. The parameter n is the ASCII code for the
character you want to type in order to cancel an input line. You
can enter the code in either hex or decimal.
For example, to change the cancel-line character to <CTRL-U>, you
would set CANLINE $15 or CANLINE 21.
If you cancel an input line in Command Mode, the line will be
terminated with a <BACKSLASH> character, and you will see a new
cmd: prompt. If you cancel a line in Converse Mode, you will see
only the <BACKSLASH> and a new line. You can cancel only the
line you are currently typing. Once a <CR> has been entered, you
can not cancel that input line using the cancel-line character.
Note that if your send-packet character is not <CR>, the
cancel-line character will cancel only the last line of a
multi-line packet. To cancel the entire packet, use the CANPAC
character.
Line cancellation, like all other input editing features, is
disabled in Transparent Mode.
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CANPAC n Default: $19 <CTRL-Y>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
CANPAC is used to change the cancel-packet input editing command
character. The parameter n is the ASCII code for the character
you want to type in order to cancel an input packet. You can
enter the code in either hex or decimal.
If you cancel a packet in Converse Mode, the line will be
terminated with a <BACKSLASH> character and a new line. You can
only cancel the packet that is currently being entered. Once you
have typed the send-packet character, or waited PACTIME (if
CPACTIME enabled), the packet can not be canceled even if it has
not been transmitted.
Packet cancellation, like other input editing features, is
disabled in Transparent Mode.
Cancel Display Output
The cancel-packet character also functions to cancel display
output in Command Mode. If you are in Command Mode and type the
cancel-packet character, any characters that would be typed on
the screen (except echoed characters) are "thrown away" by the
TNC. Typing the cancel-output character a second time restores
normal output. To see how this works, try typing DISPLAY, then
type a <CTRL-Y>. The command list display will stop. You won't
see any response from the TNC to commands. Now type another
<CTRL-Y>, and type DISPLAY again to see that the display is back
to normal.
You can use the cancel-display feature if you inadvertently do
something that causes the TNC to generate large amounts of output
to the terminal, such as giving the DISPLAY command or setting
TRACE ON. If you are in Converse Mode or Transparent Mode and
want to cancel display output, you must exit to Command Mode and
then type the cancel-packet character.
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CBELL ON|OFF Default: OFF
Display Group: I
Parameters:
ON Connect bell enabled.
OFF Connect bell disabled.
This command is used to control whether an ASCII $07 (BELL)
character is sent as part of the connected message.
When set ON, the bell character immediately precedes the asterisk
portion of the connected message, e.g.:
<BELL>*** Connected to: <callsign>
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CHECK n Default: 12
Display Group: T
Parameters:
n 0 - 250, specifying the check time in 10 second
intervals. A value of 0 disables this feature.
This command sets a connection time-out. If a link connection
exists between your TNC and another station, and the other
station "disappears," your TNC could remain in the connected
state indefinitely, refusing connections from other stations.
This might happen if propagation changes unexpectedly or an
intermediate digipeater station is turned off. In order to
prevent this sort of lockup, the TNC will try to clean up the
link if the specified time elapses without any packets being
heard from the other TNC. The operation of this feature depends
on the setting of AX25L2V2.
If AX25L2V2 is ON, the TNC will send a "check packet" to verify
the presence of the other station if no packets have been heard
from it for n*10 seconds. This frame contains no information,
but is interpreted by the receiving station's TNC as an inquiry
as to whether it is still connected. If the receiving TNC is
still connected, it sends an appropriate response packet. If the
TNC initiating the inquiry does not hear a response after RETRY+1
attempts, it commences a disconnect sequence, as if the DISCONNE
command had been given.
If AX25L2V2 is OFF and the other station has not been heard for
n*10 seconds, the TNC will not attempt an inquiry, but will send
a disconnect packet, just as if you had typed the command
DISCONNE, unless CHECKV1 is OFF. See also CHECKV1.
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CHECKV1 ON|OFF Default: OFF
Display Group: T
Parameters:
ON Enables CHECKtime (T3) when running AX.25 Level 2
Version 1.0 protocol. This will result in an automatic
disconnect when packets haven't flowed between this TNC
and the remote TNC for CHECKtime. See CHECK, above.
OFF Disables the CHECKtime timer (T3) and requires the
operator to initiate a disconnect sequence. This is in
accordance with AX.25 Level 2 Version 1.0 procedures.
When ON, the CHECK (T3) timer is used to automatically disconnect
an AX.25 Level 2 Version 1.0 link when data hasn't flowed for
CHECK time. Note that T3 is not defined for Version 1.0
operation. See CHECK, above.
When OFF, T3 is ignored and normal Version 1.0 procedures apply.
NOTE: Many operators prefer using Version 1.0 protocol,
especially on marginal or noisy links in order to eliminate some
of the overhead of AX.25 Level 2 Version 2.0 protocol.
CLKADJ n Default: 0
Display Group: T
Parameters:
n 0 - 65535, specifying the correction factor to be
applied to the real-time clock routine.
A value of "0" is a special case and means no correction factor
will be applied. If the value of CLKADJ is non-zero, then the
correction factor is calculated as:
The real-time clock routine is used to keep track of year, month,
day, hour, minute and second as specified in the DAYTIME command.
It should be noted that the real-time clock is not intended to be
your ham-shack reference clock, but is useful for approximate
time stamping information.
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CMDTIME n Default: 1
Display Group: T
Parameters:
n 0 - 250, specifying Transparent Mode time-out
value in 1 second intervals. If n is zero, the
only exit from Transparent Mode is to send a BREAK
signal or interrupt power to the TNC.
This command sets the Transparent Mode time-out value. In order
to allow escape to Command Mode from Transparent Mode while
permitting any character to be sent as data, a guard time of n
seconds is set up.
The same Command Mode entry character used for exit from Converse
Mode is used to exit Transparent Mode, but the procedure is
different. (The Command Mode entry character is set by COMMAND.)
Three Command Mode entry characters must be entered less than n
seconds apart, with no intervening characters, after a delay of n
seconds since the last characters were typed. After a final
delay of n seconds, the TNC will exit Transparent Mode and enter
Command Mode. You should then see the prompt
cmd:
The diagram below illustrates this timing.
last first second third TNC
terminal command command command now in
input mode mode mode Command
| entry entry entry Mode
| character character character |
| | | | |
| | | | |
|<---longer--->|<-shorter->|<-shorter->|<-----n----->|
than n than n than n
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CMSG ON|OFF Default: OFF
Display Group: I
Parameters:
ON The CTEXT message is sent as the first packet after a
connection is established.
OFF The CTEXT message is not sent.
CMSG enables automatic sending of the message set by CTEXT
whenever your TNC accepts a connect request from another TNC.
For example, if you have left your station running even though
you don't want to operate just now, you might want to set CMSG ON
to let people know that you can't talk when they connect to your
TNC. When you are ready to operate, you would set CMSG OFF.
CMSGDISC ON|OFF Default: OFF
Display Group: I
Parameters:
ON Automatic disconnect enabled.
OFF Automatic disconnect disabled.
This command controls whether the TNC will initiate a disconnect
sequence after it is connected to.
If CMSG is OFF, or CTEXT has no connected text, the TNC initiates
a disconnect immediately upon receiving information or
acknowledgment frames from the other station.
If CMSG is ON and CTEXT contains some text information, the TNC
initiates a disconnect after the packet containing connect text
(CTEXT) is acknowledged.
This command may be useful to bulletin board operators or others
with a need to send a short message, confirm its receipt, and
disconnect.
NOTE: Use this command with care - If you find you're able to
receive connects, yet never get data, it's possible CMSGDISC has
been left on. It's also possible is that RS-232 DCD is holding
the terminal off -- see Chapter 5 for details on hardware flow
control.
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COMMAND n Default: $03 <CTRL-C>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command is used to change the Command Mode entry character.
You can enter the code in either hex or decimal.
Command Mode is entered from Converse Mode when this character is
typed. If you type the Command Mode entry character while you
are already in Command Mode, nothing will happen. To see how
this works, enter Converse Mode by typing CONVERS. Anything you
type will become packet data. Now type a <CTRL-C>. You will see
the Command Mode prompt, indicating successful exit to Command
Mode. The display might look like this:
cmd:CONVERS
Hello World! I'm on the air on packet radio!
[enter <CTRL-C>]
cmd:
See the entry under CMDTIME for information on how to use the
Command Mode entry character to escape from Transparent Mode.
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CONMODE CONVERS|TRANS Default: CONVERS
Display Group: L
Parameters:
CONVERS Sets automatic entry to Converse Mode when a
connection is established.
TRANS Sets automatic entry to Transparent Mode when
a connection is established.
CONMODE controls which mode the TNC will be placed in after a
connection. The connection may result either from a connect
request received over the air or a connect initiated by a CONNECT
command that you issue. For most operations, you would set
CONMODE to CONVERS. However, if you are using Transparent Mode
for a bulletin board program, for example, you would set CONMODE
to TRANS so that the correct mode will be entered when your
bulletin board receives a connect request.
If you initiate a connection with the CONNECT command, the timing
of the entry into Converse or Transparent Mode is determined by
NEWMODE.
If the TNC is already in Converse or Transparent Mode when the
connection is completed, the mode will not be changed. If you
have typed part of a command line when the connection is
completed, the mode change will not take place until you complete
the command or cancel the line. This prevents the last part of
your command from inadvertently being sent as a packet.
call2 Optional callsign of TNC to be digipeated through.
As many as eight digipeat addresses can be
specified.
The part of the command line in brackets, VIA call2[,
call3...,call9] is optional. The double-bracketed text,
,call3...,call9, is also optional, but would only be used if VIA
call2 is present. The brackets are not typed.
Each callsign may include an optional sub-station ID specified as
-n immediately following the callsign. The digipeat fields are
specified in the order in which you want them to relay the
packets to the destination, call1.
CONNECT is an immediate command. It initiates a connect request
to TNC call1, optionally through digipeaters. If NEWMODE is ON,
the TNC will immediately enter Converse Mode or Transparent Mode,
as specified by the command CONMODE. If NEWMODE is OFF, the TNC
will enter Converse Mode or Transparent Mode when the connection
is successfully completed.
An error message is returned if the TNC is in a connected state,
or is already attempting to connect or disconnect. If no
response to the connect request occurs after the number of
attempts specified by RETRY, the command is aborted and a message
is typed. The TNC returns to Command Mode if NEWMODE is ON. If
NEWMODE is OFF, the mode does not change, i.e. the TNC remains in
Command Mode.
For example, to connect to WA7GXD using N0ADI-1 (who is near your
QTH) and WD0ETZ (who is near GXD's QTH) as digipeaters, you would
type
CONNECT WA7GXD VIA N0ADI-1,WD0ETZ
Packets coming back from WA7GXD access the digipeaters in the
opposite order. Thus, packets from WA7GXD will first be repeated
by WD0ETZ, then by N0ADI-1.
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CONOK ON|OFF Default: ON
Display Group: L
Parameters:
ON Connect requests from other TNCs will be accepted.
OFF Connect requests from other TNCs will be rejected.
This command determines the action taken by the TNC when a
connect request for it is received though the radio. If CONOK is
ON, the request will be acknowledged, the standard connect
message will be typed and either Converse or Transparent Mode
will be entered, depending on the setting of CONMODE.
If CONOK is OFF and the TNC is not in Transparent Mode, the TNC
will notify you of the connect attempt with the following
message.
connect request: <call>
The callsign of the station trying to connect will replace
<call>.
The TNC will also issue a DM packet, or "busy signal" to the
requesting station. The user may then issue his own connect
command. If your TNC receives a DM packet in response to a
connect request, it will type the message
*** <call> station busy
with the callsign of the station that sent the DM packet in place
of <call>.
For example, if you want to leave your station running as a
digipeater you might set CONOK OFF until you are ready for a
conversation. If you get a connect request in the meantime, you
can change your mind. Stations attempting to connect to your TNC
will be able to see that the station is up but not available for
connection (it might still be useful as a digipeater).
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CONPERM ON|OFF Default: OFF
Display Group: L
Parameters:
ON The current connection on the current stream will not
be allowed to enter the disconnected state.
OFF The current stream may be connected to and disconnected
from other stations.
This command, when switched ON, forces the TNC to always maintain
the current connection, even when frames to the other station
exceed RETRY attempts to get an acknowledgment. RESTART and
power off/on cycling will not affect this connected state.
This command only takes effect when a connection is established.
It functions on a stream-by-stream basis when multiple connec-
tions are allowed.
It is useful for certain networking applications, meteor scatter
and other noisy, less-reliable links, while still allowing con-
nections on other streams to operate normally (automatic discon-
nect based on RETRY, etc.).
CONSTAMP ON|OFF Default: OFF
Display Group: M
Parameters:
ON Connect status messages are time stamped.
OFF Connect status messages are not time stamped.
This command enables time stamping of *** CONNECTED status
messages. The date and time information is then available for
use by Bulletin Board programs or other computer applications.
The date and time must be set initially by the DAYTIME command
before time stamping will occur. The date format is determined
by the DAYUSA command.
For example, if CONSTAMP is ON, DAYUSA is ON, and the date and
time have been set, a connect message might appear as follows.
*** CONNECTED to N2WX [05/28/85 16:28:31]
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CONVERS
Display Group: NONE
CONVERS is an immediate command, and will cause the TNC to exit
from Command Mode into Converse Mode. Any link connections are
not affected. Once in Converse Mode, everything you type is
packetized and transmitted over the radio. Typing the Command
Mode entry character returns the TNC to Command Mode. See the
discussions of Converse Mode in Chapters 4 and 5.
NOTE: The letter "K" may be used to more quickly enter CONVERS
mode.
CPACTIME ON|OFF Default: OFF
Display Group: T
Parameters:
ON Packet time-out is used in Converse Mode.
OFF Packet time-out is not used in Converse Mode.
This command enables the periodic automatic sending of packets in
Converse Mode. This feature may be used for computer
communications, such as Bulletin Board operation, when the full
Transparent Mode features are not desired.
If CPACTIME is ON, characters are packetized and transmitted
periodically as they are in Transparent Mode, but local editing
and display features of Converse Mode are enabled, and software
flow control may be used. For a discussion of how periodic
packetizing works, see the command PACTIME, which controls the
rate and mode of packet assembly.
You should set CR OFF in this mode, since otherwise the
send-packet character will be inserted in the data being
packetized even though it was not typed. In order to include
<CR> characters in transmitted packets, set SENDPAC to a normally
unused character (e.g., <CTRL-P>), at which point the TNC will
treat <CR> as an ordinary character.
You can set CPACTIME ON for a mode of operation similar to full
break-in CW, in which your text is transmitted soon after you
type it, but in short bursts of a few characters, and the other
station may break in at will. Some operators find it easier to
carry on a conversation in this mode, since it eliminates the
delays while long packets are being typed.
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CR ON|OFF Default: ON
Display Group: L
Parameters:
ON The send-packet character, normally <CR>, is appended
to all packets sent in Converse Mode.
OFF The send-packet character is not appended to packets.
When CR is ON, all packets sent in Converse Mode will include, as
the last character of the packet, the send-packet character which
forces the packet to be sent. If CR is OFF, the send-packet
character is interpreted solely as a command to the TNC, not as
data to be included in the packet, and furthermore, it will not
be echoed to the terminal.
Setting CR ON and SENDPAC $0D results in a natural conversation
mode. Each line is sent when a <CR> is entered, and arrives at
its destination with a <CR> at the end of the line. If the
station at the other end reports overprinting of lines on his
display, you can set LFADD ON, or the other station can set
AUTOLF ON.
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CSTATUS
Display Group: NONE
CSTATUS is an immediate command which shows the stream identifier
and link state of all ten streams (links), the current input and
output streams, and whether or not each stream is "permanent"
(see CONPERM).
An example of a display resulting from issuing a CSTATUS command
is:
cmd:CS
A stream - IO Link state is: CONNECTED to 305MLB
B stream - Link state is: CONNECTED to AD7I P
C stream - Link state is: DISCONNECTED
D stream - Link state is: CONNECTED to N0ADI via K9NG-2
...
I stream - Link state is: CONNECT in progress
J stream - Link state is: CONNECTED to KV7B via NK6K-1
The example above shows the A stream is assigned both the input
and output streams. The B stream is connected to AD7I "perma-
nently." All other streams' states are shown as they might
normally appear with multiple connections.
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CTEXT text Default: ""
Display Group: I
Parameters:
text Any combination of characters and spaces, up to a
maximum length of 120 characters.
CTEXT specifies the text of the packet to be sent after a
connection is made, if CMSG is ON. The default text is an empty
string, i.e., no message.
You can send multiple-line messages by including carriage return
(<CR>) characters in the text. The <CR> character can be
included by using the pass character immediately preceding it
(see the PASS command). If you enter a text string longer than
120 characters, an error message will appear and the command will
be ignored.
For example, you might set your CTEXT message to
I'm not here right now, but you may leave a message.
To clear the CTEXT text without issuing a RESET command, use a %
or & as the first character in the message.
This command allows you to set the current date and time for the
TNC. The format for entering the date&time is
yymmddhhmm
where yy is the last two digits of the year, mm is the two-digit
month code (01-12), dd is date (01-31), hh is the hour (00-23),
and mm is the minute after the hour (00-59). All these codes
must be exactly two digits, so that numbers from 0 to 9 must be
entered with leading zeroes. The TNC does not check thoroughly
for the correct number of days in a month, so you should use some
judgment when you set the date.
The date&time parameter is used by the commands CONSTAMP and
MSTAMP to "time stamp" received and monitored messages. Entries
in the "heard" (displayed by MHEARD) are also time stamped if
date&time has been set. The TNC's time is updated continuously
as long as it is powered up. You must reset the date and time
each time you turn on the TNC. If you don't do this, the
commands CONSTAMP and MSTAMP will not enable time stamping.
If you type DAYTIME without a parameter, the TNC will display the
current date and time. The format of the display is dd-mm-yy
hh:mm if DAYUSA is OFF, and mm/dd/yy hh:mm if DAYUSA is ON. The
format for entering date&time is not affected. For example,
cmd:DAYTIME 8402291530
sets the date and time to February 29, 1984 at 3:30 P.M. The
display of the date and time, with DAYUSA ON would be:
cmd:DAYTIME
02/29/84 15:30:26
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DAYUSA ON|OFF Default: ON
Display Group: M
Parameters:
ON Date is displayed in the format mm/dd/yy.
OFF Date is displayed in the format dd-mm-yy.
This command determines the format for the TNC's display of the
date. If DAYUSA is ON, the standard U.S. format is used; if
DAYUSA is OFF, the standard European format is used. This
command affects the format of the date display used in "time
stamps" as well as the display when DAYTIME is entered without
parameters. The format for entering the time using DAYTIME is
not affected.
For example, if DAYUSA is ON, then July 2, 1984 at 9:28:44 AM
would be displayed as
cmd:DAYTIME
07/02/84 9:28:44
If DAYUSA is OFF the same date and time would appear as
cmd:DAYTIME
02-07-84 9:28:44
DEADTIME n Default: 33
Display Group: T
Parameters:
n 0-250 in 10 mSec increments.
DEADTIME specifies the time it takes a station's receiver to
detect the fact that a remote transmitter has keyed up. It
should be set to the time of the slowest acceptable radio on the
channel. It must also allow for any squelch delays and DCD lock
time. DWAIT and TXDELAY should also be set to this same value
for everyone in the LAN.
A fairly fast VHF FM radio-plus-TNC might take 210 mSec (DEA 21),
while an HF radio-plus-TNC will usually respond in 80 mSec (DEA
8). Some multi-mode radio-plus-TNCs operating at 1200 bps may
respond in only 40 mSec (DEA 4). The default value (DEA 33) will
safely cover the majority of FM radios in common packet use.
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DELETE ON|OFF Default: OFF
Display Group: C
Parameters:
ON The delete character input editing character is
<DELETE> ($7F).
OFF The delete character input editing character is
<BACKSPACE> ($08).
This command is used to change the input editing command for
character deletion. When this character is typed, the last
character from the input line is deleted. How the TNC indicates
the deletion is controlled by the BKONDEL command.
You can not use this character to delete past the beginning of a
line, although you can delete <CR> characters that have been
entered in the text with the pass character.
To see a corrected display of the current line after you have
deleted characters, type the redisplay-line character, which is
set by the REDISPLA command.
This command does not work while in transparent mode.
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DIGIPEAT ON|OFF Default: ON
Display Group: L
Parameters:
ON The TNC will digipeat packets if requested.
OFF The TNC will not digipeat packets.
When this parameter is ON, any packet received that has your
TNC's callsign (including SSID) in the digipeat list of its
address field will be retransmitted. Each station included in
the digipeat list relays the packet in its turn, marking the
packet so that it will not accidentally relay it twice (unless so
requested), and so that the stations will relay the packet in the
correct order. Digipeating takes place concurrently with other
TNC operations and does not interfere with normal operation of a
packet station.
In the spirit of cooperation typical of Amateur operation, you
will probably want to set DIGIPEAT ON most of the time. However,
you might want to disable digipeating if you're not home, or if
your transmit relay makes enough noise to wake you up at night.
The command HID enables automatic transmission of identification
packets if your station is acting as a digipeater.
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DISCONNE
Display Group: NONE
DISCONNE is an immediate command. It will initiate a disconnect
request with the currently connected station. A successful
disconnect results in the display of:
*** DISCONNECTED
Other commands may be entered while the disconnect is taking
place, although connects are disallowed until the disconnect is
completed. If the retry count is exceeded while waiting for the
other station to acknowledge, the TNC moves to the disconnected
state. If a disconnect command is entered while the TNC is
disconnecting, the retry count is immediately set to the maximum
number. In either case, the disconnect message is
*** retry count exceeded
*** DISCONNECTED
Disconnect messages are not displayed when the TNC is in
Transparent Mode.
DISPLAY [class]
Display Group: NONE
Parameters:
class Optional parameter-class identifier, one of the
following:
ASYNC display asynchronous port parameters
CHARACTE display special characters
HEALTH display health counters/LEDs
ID display ID parameters
LINK display link parameters
MONITOR display monitor parameters
TIMING display timing parameters
DISPLAY is an immediate command, and with no class parameter will
cause all control parameters and their current values to be
displayed. Sub-groups of related parameters can be displayed by
specifying the optional parameter-class (e.g., DISPLAY A will
list all the asynchronous port parameters). Individual
parameters can be displayed by entering the parameter name with
no options (e.g., entering AWLEN will cause the present value of
AWLEN to be displayed).
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DWAIT n Default: 33
Display Group: T
Parameters:
n 0 - 250, specifying default wait time in 10 ms
intervals.
This value is used to avoid collisions with digipeated packets.
The TNC will wait the default wait time after last hearing data
on the channel before it begins its own keyup sequence, unless
the TNC is waiting to transmit digipeated packets. This value
should be agreed on by all members of a local area when
digipeaters are used in the area. The best value will be
determined by experimentation, but will be a function of the
keyup time (TXDELAY) of the digipeater stations.
This feature is intended to help alleviate the drastic reduction
of throughput that occurs on a channel when digipeated packets
suffer collisions. It is necessary because digipeated packets
are not retried by the digipeater, but must be restarted by the
originating station. If all stations specify a default wait
time, and the right value of n is chosen, the digipeater will
capture the frequency every time it has data to send, since
digipeated packets are sent without this delay.
NOTE: DWAIT is used for other purposes in many LANs. Do not set
DWAIT to 0 just because you think there are no digipeaters in use
on the channel you are occupying!
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ECHO ON|OFF Default: ON
Display Group: A
Parameters:
ON Characters received from the computer or terminal are
echoed by the TNC.
OFF Characters are not echoed.
This command controls local echoing by the TNC when it is in
Command or Converse Mode. Local echoing is disabled in
Transparent Mode.
If you don't see your input on the display, you should set ECHO
ON. If you see two copies of every character you type, you
should set ECHO OFF. If you see the characters you type
displayed correctly, you have ECHO set correctly.
ESCAPE ON|OFF Default: OFF
Display Group: A
Parameters:
ON The <ESCAPE> character ($1B) is output as "$" ($24).
OFF The <ESCAPE> character is output as <ESCAPE> ($1B).
This command specifies the character which will be output when an
<ESCAPE> character is to be sent to the terminal. The <ESCAPE>
translation is disabled in Transparent Mode.
This command is provided because some terminals, and computer
programs that emulate such terminals, interpret the <ESCAPE>
character as a special command prefix. Such terminals may alter
their displays depending on the characters following the
<ESCAPE>. If you have such a terminal, you can protect yourself
from unexpected text sequences and from other packeteers by
setting ESCAPE ON.
See also the MFILTER command, which allows general character
stripping (rather than character translation) in monitored
packets.
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FIRMRNR ON|OFF Default: ON
Display Group: L
Parameters:
ON When this TNC's buffers fill, an RNR is sent. When the
buffers are no longer full, an RR command frame is
sent.
When this TNC receives an RNR, it will not poll the sending TNC
until [T0*10 seconds]. T0 = CHECKtime*8 unless CHECKtime*8 is
<30 or >253 in which case T0 = 12.
OFF When this TNC's buffers fill, an RNR is sent as a
response to an I frame.
When this TNC receives an RNR, it will resend the data every
FRACKtime (T1) until an RR is received.
When OFF, standard AX.25 Level 2 Version 2.0 protocol procedures
are used. If a TNC sending data receives an RNR, meaning the
remote TNC cannot accept more data, the sending TNC will
continuously re-send the data every T1 (FRACK) time until an RR
is received, meaning the remote TNC accepted the data. This
often results in a lot of unnecessary channel congestion.
When FIRMRNR is ON, this TNC will stop sending data upon receipt
of an RNR. If the remote TNC does not send an RR before [T0]
(see above), this TNC will poll the remote TNC to be sure it is
still active. If this TNC sent the RNR, then it will send an RR
when its buffers have cleared to allow more data to be received.
NOTE: The remote TNC should be capable of FIRMRNR operation.
This mode is operable with all TNCs having a FIRMRNR settable to
ON, and with most network nodes. If the remote TNC is not
capable of FIRMRNR operation, and if the channel is poor, there
will be additional delays in getting data passed between the
TNCs.
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FLOW ON|OFF Default: ON
Display Group: A
Parameters:
ON Type-in flow control is active.
OFF Type-in flow control is disabled.
When type-in flow control is enabled, any character entered from
the terminal will halt output to the terminal until: (1) a
packet is forced (in Converse Mode); (2) a line is completed (in
Command Mode); (3) the packet length is exceeded; or (3) the
terminal output buffer fills up. Canceling the current command
or packet or typing the redisplay-line character will also cause
output to resume. Type-in flow control is not used in
Transparent Mode.
Setting FLOW ON will keep received data from interfering with
data entry. If you (and the person you are talking to) wait for
a packet from the other end before starting to respond, you can
set FLOW OFF. Some Bulletin Board programs may work best with
FLOW OFF. Some computers with "software UARTs" may be unable to
send and receive data at the same time; users of such computers
should set FLOW ON.
FRACK n Default: 8
Display Group: T
Parameters:
n 0 - 15, specifying frame acknowledgment time-out
(T1) in 1 second intervals.
After transmitting a packet requiring acknowledgment, the TNC
will wait for the frame acknowledgment time-out before
incrementing the retry counter and sending the frame again. If
the packet address includes digipeater requests, the time between
retries will be adjusted to
Retry interval = n * (2*m + 1)
where m is the number of digipeaters.
When a retried packet is sent, a random wait time is added to any
other wait times in use. This is to avoid lockups in which two
TNCs repeatedly send packets which collide with each other.
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FULLDUP ON|OFF Default: OFF
Display Group: L
Parameters:
ON Full duplex mode is enabled.
OFF Full duplex mode is disabled.
When full duplex mode is disabled, the TNC makes use of the Data
Carrier Detect signal from the modem to avoid collisions, and
acknowledges multiple packets in a single transmission with a
single acknowledgment. When full duplex mode is enabled, the TNC
ignores the DCD signal and acknowledges packets individually.
The latter mode is useful for full-duplex radio operation, such
as through the Microsats. It should not be used unless both your
station and the station you are communicating with are
full-duplex stations.
You may find full-duplex mode useful for some testing operations,
such as analog- or digital-loopback tests.
Note that certain timers, such as DWAIT, are disabled when in
FULLDUP mode.
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HEADERLN ON|OFF Default: OFF
Display Group: M
Parameters:
ON The header for a monitored packet is printed on a
separate line from the packet text.
OFF The header and packet text of monitored packets are
printed on the same line.
This command affects the display format for monitored packets.
If HEADERLN is OFF, the address information is displayed with the
packet:
KV7D>N2WX: Go ahead and transfer the file.
If HEADERLN is ON, the address information is displayed, followed
by the packet text on a separate line:
N2WX>KV7D:
Sorry, I'm not quite ready yet.
If you have set MRPT ON or enabled MSTAMP, you may wish to set
HEADERLN ON, as the packet header quickly becomes long enough to
fill a line when these functions are active.
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HEALLED ON|OFF Default: OFF
Display Group: H
Parameters:
ON The TNC will "dither" the CON and STA LEDs.
OFF The TNC will control the CON and STA LEDs in normal
fashion.
This command allows the user to redefine the functions of the two
CPU controllable LEDs (i.e. the STAtus and CONnect LEDs).
When HEALLED is set ON, the two LEDs flash in a seeming random
fashion. At a glance, the user may make a judgment on whether
the software has crashed, since the LEDs will probably not flash
if the software fails catastrophically.
With HEALLED set OFF, the LEDs function normally. The CON LED
glows when the current stream is in the connected or
disconnecting state, and the STA LED glows when the current
stream has unacknowledged packets in the transmit buffer.
HID ON|OFF Default: OFF
Display Group: I
Parameters:
ON Enables HDLC identification by a digipeater.
OFF Disables HDLC identification.
This command is used to enable or disable the sending of
identification packets by the TNC. If HID is OFF, the TNC will
never send an identification packet. If HID is ON, the TNC will
send an identification packet every 9.5 minutes if the station is
digipeating packets. The ID command allows the operator to send
a final identification packet if the station is being taken off
the air.
An identification consists of an unsequenced information (UI)
frame whose data field is your station identification. The
identification packet is addressed to the "CQ" address set by the
UNPROTO command. Your station identification is your callsign as
set by MYCALL, with "/R" appended.
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ID
Display Group: NONE
ID is an immediate command. It will send a special identi-
fication packet. ID can be used to force a final identification
packet to be sent as a digipeater station is being taken off the
air. The identification packet will be sent only if the
digipeater has transmitted since the last automatic
identification.
An identification consists of an UI frame whose data field is
your station identification. The identification packet is
addressed to the "CQ" address set by the UNPROTO command. Your
station identification is your callsign as set by MYCALL, with
"/R" appended.
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KISS ON|OFF Default: OFF
Display Group: L
Parameters:
ON Serial Line Interface Protocol (SLIP) is used between
the TNC and the attached computer. The TNC executes a
very limited instruction set, arbitrating channel
access only and depending on the computer to handle all
Level Two and higher protocol issues.
OFF The TNC operates using the commands and messages
documented herein. This is the normal mode of
operation.
This command is used to enter the "KISS" mode for operation with
various experimental protocols. KISS is used with intelligent
host computers. The most popular use has been in conjunction
with the KA9Q TCP/IP networking software, available from TAPR and
elsewhere.
To operate KISS with this release, enter the command KISS ON,
then the command RESTART (NOT RESET!). The CON and STA LEDs will
flash three times when initially activated. This command will
then have effect for subsequent power on/off cycles. To return
to normal operation, enter the command PARAM <device> 255 at the
NET>
prompt if you are running the KA9Q TCP/IP software package. If
you are not using this package, send the three bytes $C0, $FF,
$C0 to the TNC to restore normal operation. If you cannot send
these character values with the software you intend to use, you
must power the TNC off, then disconnect the bbRAM battery for
several minutes, then reconnect the battery and power up again to
restore normal operation.
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The commands available in Kiss Mode are:
Command Function Comments
0 Data Frame The rest of the frame is data to be
sent.
1 TXDELAY The next byte is is the transmitter keyup
time in 10 mSec units, with a default of 50
(500 mSec).
2 P The next byte is the persistence parameter,
p, scaled to the range 0-255. The
probability of transmitting at the next
opportunity is p/255. The default is 64 (for
a probability of 0.25).
3 SlotTime The next byte is the slot interval in 10 mSec
increments. The default is 10 (100 mSec).
4 TXtail The next byte is the time to hold the
transmitter after the FCS has been sent,
in 10 mSec units. The command is
obsolete and is included for
completeness with earlier im-
plementations.
5 FullDuplex The next byte is 0 for half-duplex
(normal) or any other number for full
duplex (e.g., for operation with
MicroSats).
FF Return Exit KISS and resume normal TNC operation.
NOTE: The TNC will only return type 0 frames (received
information). Thus, the computer cannot interrogate the TNC to
find the values of the other command types.
KISSM {immediate command}
This command may be used to cause the TNC to immediately begin
running the KISS code.
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LCALLS call1[,call2...,call8] Default: ""
Display Group: M
Parameters:
call Callsign list. Up to 8 calls, separated by commas.
Each callsign may include an optional sub-station ID specified as
-n immediately following the call. This command works in
conjunction with BUDLIST and allows selective monitoring of other
packet stations. These two commands determine which packets will
be displayed when you have set MONITOR ON. BUDLIST specifies
whether the callsigns in the list are the ones you want to ignore
or, alternatively, are the only ones you want to listen to.
If you want to listen only for packets from a limited list, you
should enter your selected list with LCALLS and set BUDLIST ON.
If you want to ignore packets from a limited list, you should
list the callsigns to ignore in LCALLS and set BUDLIST OFF.
The list of calls in the LCALLS buffer is saved in battery-backed
RAM. The calls may be cleared without issuing a RESET command by
entering a "%" or a "&" character as a callsign.
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LCOK ON|OFF Default: ON
Display Group: A
Parameters:
ON The TNC will send lower case characters to the computer
or terminal.
OFF The TNC will translate lower case characters to upper
case.
If LCOK is OFF, lower case characters will be translated to upper
case before being output to the terminal. This case translation
is disabled in Transparent Mode. Input characters and echoes are
not case translated.
If your computer or terminal does not accept lower case
characters it may react badly if the TNC sends such characters to
it. This command allows you to translate all lower case
characters received in packets, as well as messages from the TNC,
to upper case.
Since echoes of the characters you type are not translated to
upper case, you can use this command to make your display easier
to read when you are conversing in connected mode. If you and
the other station's operator set LCOK OFF, you can each type your
own messages in lower case and see incoming packets displayed in
upper case. This makes it easy to distinguish incoming and
outgoing lines.
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LCSTREAM ON|OFF Default: ON
Display Group: C
Parameters:
ON The TNC will translate the character immediately
following the STREAMSWITCH character to upper case
before processing it.
OFF The TNC will process the character immediately
following the STREAMSWITCH character as it is entered.
When operating multi-connect, the user must enter a stream
identifier (default A through J) after the STREAMSWITCH character
(default |) to select a new logical stream to send data.
Normally, the stream identifier must be in upper case, or an
error message will result.
When LCSTREAM is ON, the character immediately following the
streamswitch character is converted to upper case before being
acted upon. Thus, the case (upper or lower) becomes
insignificant. Use of LCSTREAM is useful if you are typing in
lower case and don't want to be bothered with remembering to
switch to upper case when changing streams.
LFADD ON|OFF Default: OFF
Display Group: L
Parameters:
ON A <LF> character is added to outgoing packets following
each <CR> transmitted in the packet.
OFF No <LF> is added to outgoing packets.
This function is similar to AUTOLF, except that the <LF>
characters are added to outgoing packets rather than to text
displayed locally. This feature is included in order to maintain
compatibility with other packet radio controllers. If the person
you are talking to reports overprinting of packets from your
station you should set LFADD ON. This character insertion is
disabled in Transparent Mode.
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LFIGNORE ON|OFF Default: OFF
Display Group: L
Parameters:
ON TNC will ignore <LF> characters.
OFF TNC will respond to <LF> characters.
This command controls whether TNC 2 responds to ASCII Line Feed
(<LF> $0A) characters or ignores them in command and converse
modes.
When turned on, line feeds are totally ignored except in trans-
parent mode.
MALL ON|OFF Default: ON
Display Group: M
Parameters:
ON Monitored packets include both "connected" packets and
"unconnected" packets.
OFF Monitored packets include only "unconnected" packets.
This command determines the class of packets which are monitored.
If MALL is OFF, only otherwise eligible packets (as determined by
the BUDLIST and LCALLS commands) sent by other TNCs in the
unconnected mode are displayed. This is the normal manner of
operation when this TNC is being used to talk to a group of TNCs
all of which are unconnected.
If MALL is ON, all otherwise eligible frames are displayed,
including those sent between two other connected TNCs. This mode
may be enabled for diagnostic purposes or for "reading the mail."
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MAXFRAME n Default: 4
Display Group: L
Parameters:
n 1 - 7, signifying a number of packets.
MAXFRAME sets an upper limit on the number of unacknowledged
packets which the TNC can have outstanding at any one time. This
is also the maximum number of contiguous packets which can be
sent during any given transmission. If some but not all of the
outstanding packets are acknowledged, a smaller number may be
transmitted the next time, or new frames may be included in the
retransmission, so that the total unacknowledged does not exceed
n.
If you perform file transfers, you should experiment with
MAXFRAME and PACLEN. If the link is good, there is an optimum
relationship between the parameters set by these commands so that
the maximum number of characters outstanding does not exceed the
packet receive buffer space of the TNC receiving the data.
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MCOM ON|OFF Default: OFF
Display Group: M
Parameters:
ON Connect, disconnect, UA, DM, I and UI frames are
monitored.
OFF Only information frames (I and UI) are monitored.
This command enables monitoring of connect and disconnect frames
when MONITOR is ON. When MCOM is OFF, only I frames (packets
containing user information) will be displayed.
When MCOM is on, all control fields are decoded (invalid ones are
marked with ????). For I and S frames, sequence number
information is also presented. Frames compatible with the AX.25
Level 2.0 standard are also decoded as to the state of the
Command/Response (C/R) and Poll/Final (P/F) bits.
Ex: WA7GXD>KV7B <I C S0 R0>:
Hi Dan,
WA7GXD>KV7B <I C P S1 R0>:
have you been on EIES lately?
KV7B>WA7GXD <RR R F R2>
KV7B>WA7GXD <I C P S1 R2>:
I was just thinking about that. I heard that
@(username) made some real unbelievable comment on it!
WA7GXD>KV7B <RR R F R2>
WB2SPE>KV7B <C>
KV7B>WB2SPE <DM>
KV7B>WA7GXD <I C P S2 R2):
Good conditions now...
WA7GXD>KV7B <RR R F R3>
WA7GXD>KV7B <I C P S2 R3>:
Yes @(username) did. It was quite remarkable.
As with other monitor commands, the stations monitored are
determined by BUDLIST and LCALLS.
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MCON ON|OFF Default: ON
Display Group: M
Parameters:
ON Monitor mode remains active when the TNC is connected.
OFF Monitor mode is disabled while the TNC is connected.
If MCON is ON, the MONITOR command will enable monitoring while
your TNC is connected to another TNC. If MCON is OFF, the
display of monitored packets is suspended when a connect occurs,
and is resumed when the TNC is disconnected.
If you want to see all packets displayed when you are not
connected but have such display suppressed when you connect to
another station, you should set MCON OFF.
MFILTER n1[,n2[,n3[,n4]]] Default: None
Display Group: M
Parameters:
n 0 - $7F, specifying an ASCII character code. Up
to 4 characters may be specified.
This command allows you to specify characters to be "filtered,"
or eliminated from monitored packets. The parameters n1, n2,
etc., are the ASCII codes for the characters you want to filter.
You can enter the code in either hex or decimal.
For example, if a <CTRL-L> character causes your screen to be
cleared, and you don't want this to happen, you can set MFILTER
12. If you also want to eliminate <CTRL-Z> characters, which
some computers interpret as end-of-file markers, you can set
MFILTER 12,26.
MHCLEAR
Display Group: NONE
MHCLEAR is an immediate command. It causes the list of stations
heard to be cleared. You can use this command in conjunction
with MHEARD to keep track of the stations on the air over a given
period of time, such as an evening or a week. Clear the list of
stations heard when you first begin to monitor the packet
activity.
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MHEARD
Display Group: NONE
MHEARD is an immediate command. It causes the TNC to display the
list of stations that have been heard since the last time the
command MHCLEAR was given. Stations that are heard through
digipeaters are marked with a * in the heard log. If you clear
the list of stations heard at the beginning of a session, you can
use this command to easily keep track of the stations that are
active during that period. The maximum number of heard stations
that can be logged is 18. If more stations are heard, earlier
entries are discarded. Logging of stations heard is disabled
when PASSALL is ON.
If the DAYTIME command has been used to set the date and time,
entries in the heard log will be time stamped. For example,
Note that no daytime string is displayed next to N2WX. This
indicates that when N2WX was last heard the clock had not been
set.
MNONAX25 ON|OFF Default: OFF
Display Group: M
Parameters:
ON Monitors all frames with valid CRC.
OFF Monitors AX.25 Level 2 Protocol frames with no
higher-level protocols (PID = F0).
When OFF, only AX.25 Level 2 protocol frames will be displayed.
Any packets with level 3 or level 4 protocols will be inhibited.
Thus, NET/ROM, TCP/IP, ROSE, etc., networking frames will not be
displayed. These frames often have binary values buried in them
which cause undesirable responses on a normal screen display.
When ON, any packet or frame with a valid CRC will be displayed
regardless of protocol.
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MONITOR ON|OFF Default: ON
Display Group: M
Parameters:
ON Monitoring of packet activity is enabled.
OFF Monitoring of packet activity is disabled.
If MONITOR is ON and the TNC is not in Transparent Mode, packets
not addressed to your TNC may be displayed. The addresses in the
packet are displayed along with the data portion of the packet,
e.g.:
N2WX>W5FD-3: I'm ready to transfer the file now.
The calls are separated by a ">" and the sub-station ID field
(SSID) is displayed if it is other than 0. The MALL, BUDLIST,
and LCALLS commands determine which packets are to be monitored.
The MCON command controls the action of monitor mode when the TNC
is connected. All monitor functions are disabled in Transparent
Mode.
The format of the monitor display is controlled by HEADERLN. If
you want to see the station addresses on a separate line from the
text, you can set HEADERLN ON. MRPT enables monitoring of the
digipeater route as well as source and destination addresses for
each packet. MSTAMP includes a time stamp with the addresses if
DAYTIME has been set.
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MRPT ON|OFF Default: ON
Display Group: M
Parameters:
ON Display the stations in the digipeat path for monitored
packets.
OFF Display only the source and destination stations for
monitored packets.
This command affects the way monitored packets are displayed. If
MRPT is OFF, only the originating station and the destination are
displayed for monitored packets. If MRPT is ON, the entire
digipeat list is displayed for monitored packets, and stations
that have already relayed the packet are indicated with an
asterisk.
For example,
WB9FLW>AD7I,K9NG*,N2WX-7:Hi Paul.
This packet, sent from WB9FLW to AD7I, has been relayed by K9NG
but not by N2WX-7. With MRPT OFF, the same packet would be
displayed as
WB9FLW>AD7I:Hi Paul.
Setting MRPT ON increases the length of the address display, and
you may wish to set HEADERLN ON as well to display this informa-
tion on a separate line.
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MSTAMP ON|OFF Default: OFF
Display Group: M
Parameters:
ON Monitored frames are time stamped.
OFF Monitored frames are not time stamped.
This command enables time stamping of monitored packets. The
date and time information is then available for use for automatic
logging of packet activity or other computer applications. The
date and time are set initially by the DAYTIME command, and the
date format is determined by the DAYUSA command.
Setting MSTAMP ON increases the length of the address display,
and you may wish to set HEADERLN ON as well to display this
information on a separate line.
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MYALIAScall[-n] Default: <blank>
Display Group: I
Parameters:
call Alternative identity of your TNC.
n 0 - 15, an optionally specified sub-station ID
(SSID).
This command specifies an alternative callsign (in addition to
the callsign specified in MYCALL) for use as a digipeater only.
In some areas, wide coverage digipeaters operators have changed
the callsign of their machine to a shorter and (usually) easier
to remember identifier. International Civil Aviation Organiza-
tion (ICAO) airport identifiers, sometimes combined with tele-
phone area codes, have been used.
Use of this command permits HID to identify normally with the
MYCALL-specified callsign yet permit an alternative (alias)
repeat-only "callsign."
MYCALL call[-n] Default: NOCALL-0
Display Group: I
Parameters:
call Callsign of your TNC.
n 0 - 15, an optionally specified sub-station ID
(SSID).
This command tells the TNC what its callsign is. This callsign
will be placed in the FROM address field for all packets
originated by your TNC. It will accept frames with this callsign
in the TO field and relay frames with this callsign in the
digipeat field (if DIGIPEAT is ON). MYCALL will also be used for
identification packets (see HID and ID).
The default callsign must be changed for proper operation of the
protocols. There should never be more than one station with the
same callsign (including SSID) on the air at once. The SSID can
be used to distinguish two stations with the same Amateur call.
The SSID will be 0 unless explicitly set to another value.
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NEWMODE ON|OFF Default: OFF
Display Group: L
Parameters:
ON Switching to data transfer mode occurs at the time of
connection, or the issuing of the CONNECT command, and
return to command mode is automatic at the time of
disconnection.
OFF Switching to data transfer mode occurs at time of
connection and no return to command mode occurs at
disconnection.
The NEWMODE command may be used to select the way the TNC behaves
when connections are made and broken.
If NEWMODE is OFF, the TNC will remain in Command Mode after you
issue a CONNECT command until a connection is actually
established. When the connection is established, the TNC will
enter Converse Mode or Transparent Mode, depending on the setting
of CONMODE. When the connection is terminated, the TNC remains
in Converse or Transparent Mode unless you have forced it to
return to Command Mode. This is the same as the behavior of TNC
1 (running version 3.x software) under these conditions.
If NEWMODE is ON, the TNC will enter Converse Mode or Transparent
Mode as soon as you issue a CONNECT command, without waiting for
the connection to be established. Anything you type will be
packetized to be transmitted once the connection is complete.
When the connection is broken, or if the connect attempt fails,
the TNC will return to Command Mode.
If you have a Bulletin Board program designed to work with TNC 1
you should set NEWMODE OFF if the program relies on the sequence
of actions used by TNC 1. Otherwise, you should choose the
setting for NEWMODE that seems most convenient to you.
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NOMODE ON|OFF Default: OFF
Display Group: L
Parameters:
ON The TNC will only switch modes (command, converse or
transparent) upon explicit command.
OFF The TNC will switch modes in accordance with the
setting of NEWMODE.
When NOMODE is ON, the TNC will never change between CONVERSE or
TRANSPARENT mode to COMMAND mode (or vice-versa) on its own.
Only user commands (CONV, TRANS, or ^C) may change the type-in
mode.
If NOMODE is OFF, then automatic mode switching is handled
according to the setting of the NEWMODE command.
NUCR ON|OFF Default: OFF
Display Group: A
Parameters:
ON <NULL> characters are sent to the terminal following
<CR> characters.
OFF <NULL> characters are not sent to the terminal
following <CR> characters.
This command causes transmission of <NULL> characters (ASCII code
$00), producing an effective delay following any <CR> sent to the
terminal. The number of <NULL> characters is determined by the
command NULLS. This delay is required by some hardcopy
terminals. You need to set NUCR ON if your terminal misses one
or more characters after responding to a <CR>. If this is the
case, you will sometimes see overtyped lines.
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NULF ON|OFF Default: OFF
Display Group: A
Parameters:
ON <NULL> characters are sent to the terminal following
<LF> characters.
OFF <NULL> characters are not sent to the terminal
following <LF> characters.
This command causes transmission of <NULL> characters (ASCII code
$00), producing an effective delay following any <LF> sent to the
terminal. The number of <NULL> characters is determined by the
command NULLS. This delay is required by some display terminals.
You need to set NULF ON if your terminal sometimes misses
characters at the beginning of the line.
NULLS n Default: 0
Display Group: A
Parameters:
n 0 - 30, specifying the number of <NULL> characters
to send after <CR> or <LF>.
This command specifies the number of <NULL> characters (ASCII
code $00) to send to the terminal after a <CR> or <LF> is sent.
In addition to setting this parameter value, NUCR and/or NULF
must be set to indicate whether nulls are to be sent after <CR>,
<LF>, or both. Devices requiring nulls after <CR> are typically
hard-copy devices requiring time for carriage movement. Devices
requiring nulls after <LF> are typically CRTs which scroll
slowly. Extra null characters are sent only in Converse and
Command Modes.
OUT nn 0<=nn<=255
The value 'nn' is sent to the TNC's z/80 i/o port 0BFH. Note
that the last value 'nn' is sent to the i/o port frequently, but
not immediately. In this context, 'frequently' means many times
per second, and 'not immediately' means within at most 100ms.
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PACLEN n Default: 128
Display Group: L
Parameters:
n 0 - 255, specifying the maximum length of the data
portion of a packet. The value 0 is equivalent to
256.
The TNC will automatically transmit a packet when the number of
input bytes for a packet reaches n. This value is used in both
Converse and Transparent Modes.
If you perform file transfers, you should experiment with both
MAXFRAME and PACLEN. If the link is good, there is an optimum
relationship between the parameters set by these commands so that
the maximum number of characters outstanding does not exceed the
packet receive buffer space of the TNC receiving the data.
Note: Although there is no requirement for two TNCs exchanging
data to have the same PACLEN value, allowing more than 128
characters of data in a packet may be incompatible with some
varieties of TNCs.
PACTIME EVERY|AFTER n Default: AFTER 10
Display Group: T
Parameters:
n 0 - 250, specifying 100 ms intervals.
EVERY Packet time-out occurs every n*100 milliseconds.
AFTER Packet time-out occurs when n*100 milliseconds
elapse with no input from the computer or
terminal.
This parameter is always used in Transparent Mode, and will also
be used in Converse Mode if CPACTIME is ON. When EVERY is
specified, input bytes are packaged and queued for transmission
every n*100 ms. When AFTER is specified, bytes are packaged when
input from the terminal stops for n*100 ms. In no case will a
zero length packet be produced, and the timer is not started
until the first byte is entered. A value of 0 for n is allowed,
and causes packets to be generated with no wait time.
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PARITY n Default: 3 (even)
Display Group: A
Parameters:
n 0 - 3, selecting a parity option from the table
below.
This command sets the parity mode for terminal or computer data
transfer according to the following table:
n Parity
0 no parity
1 odd parity
2 no parity
3 even parity
The parity bit, if present, is automatically stripped on input
and not checked in Command Mode and Converse Mode. In
Transparent Mode, all eight bits, including parity if any, are
transmitted in packets. If "no parity" is set and AWLEN is 7,
the eighth bit will be set to 0 in Transparent Mode.
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PASS n Default: $16 <CTRL-V>
Display Group: C
Parameter:
n 0 - $7F, specifying an ASCII character code.
This command selects the ASCII character used for the "pass"
input editing command. The parameter n is the ASCII code for the
character you want to type in order to include the following
character in a packet or text string. You can enter the code in
either hex or decimal.
You can use this character to send any character in packets, even
though that character may have some special function. For
example, suppose you have set COMMAND 3, specifying that <CTRL-C>
is your Command Mode entry character. If you use a Bulletin
Board program that requires a <CTRL-C> to escape from some
operation, you will type
<CTRL-V> <CTRL-C>
to insert a <CTRL-C> character in your packet. Of course, if you
do this frequently you would be better off to change your Command
Mode entry character.
A common use for the pass character is to allow <CR> to be
included in the BTEXT and CTEXT messages. Similarly, you can
include <CR> in text when you are in Converse Mode, to send
multi-line packets. (The default send-packet character is <CR>.)
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PASSALL ON|OFF Default: OFF
Display Group: L
Parameters:
ON TNC will accept packets with invalid CRCs.
OFF TNC will only accept packets with valid CRCs.
This command causes the TNC to display packets received with
invalid CRC fields. Packets are accepted for display despite CRC
errors if they consist of an even multiple of 8 bits and up to
339 bytes. The TNC will attempt to decode the address field and
display the callsign(s) in the standard monitor format, followed
by the text of the packet.
This mode is not normally enabled, since rejection of any packet
with an invalid CRC field is what insures that received packet
data is error-free. This mode might be enabled for testing a
marginal RF link or during operation under other unusual
circumstances.
If you set PASSALL ON and monitor a moderately noisy channel you
will periodically see "packets" displayed in this mode, since
there is no basis for distinguishing actual packets received with
errors from random noise.
Logging of stations heard (for display by MHEARD) is disabled
whenever PASSALL is ON, since the callsigns detected may be
incorrect.
call2 Optional callsign(s) of TNC(s) to be digipeated
through. As many as eight digipeater addresses
may be specified.
RECONNECT is an immediate command. It may be used to change the
path through which you are currently connected to a station. It
may only be used when your TNC is connected on the current
stream.
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REDISPLA n Default: $12 <CTRL-R>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command is used to change the redisplay-line input editing
character. The parameter n is the ASCII code for the character
you want to type in order to redisplay the current input line.
You can enter the code in either hex or decimal.
You can type this character to cause the TNC to retype a line you
have begun. When you type the redisplay-line character, the
following things happen: First, type-in flow control is
temporarily released (if it was enabled). This displays any
incoming packets that are pending. Then a <BACKSLASH> character
is typed, and the line you have begun is retyped on the next
line. If you have deleted and retyped any characters, only the
final form of the line will be shown. You are now ready to
continue typing where you left off.
You can use the redisplay-line character to see a "clean" copy of
your input if you are using a printing terminal and you have
deleted characters. If you have set BKONDEL OFF, deletions are
designated with <BACKSLASH> characters, rather than by trying to
correct the input line display. The redisplayed line will show
the corrected text.
You can also use this character if you are typing a message in
Converse Mode and a packet comes in. You can see the incoming
message before you send your packet, without concealing your
input.
RESET
Display Group: NONE
This is an immediate command. It sets all parameters to their
default settings and re-initializes the TNC.
WARNING: All parameter customizing and monitor lists will be
lost.
If you want to re-initialize the TNC using the parameter values
in battery backed-up RAM, you should turn the TNC off then on
again, or issue the RESTART command.
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RESPTIME n Default: 0
Display Group: T
Parameters:
n 0 - 250, specifying 100 ms intervals.
This command sets a minimum delay that is imposed on acknow-
ledgment packets. This delay may run concurrently with default
wait set by DWAIT and any random wait in effect.
This delay can be used to increase throughput during operations
such as file transfer when the sending TNC usually sends the
maximum number of full-length packets. Occasionally, the sending
TNC may not have a packet ready in time to prevent transmission
from being stopped temporarily, with the result that the
acknowledgment of earlier packets collides with the final packet
of the series. If the receiving TNC sets RESPTIME to 10, say,
these collisions will be avoided.
When using priority acknowledgment (see ACKPRIOR), this value
must be set to 0 for proper operation.
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RESTART
Display Group: NONE
RESTART is an immediate command. It re-initializes the TNC using
the defaults stored in bbRAM. The effect of this command is the
same as turning the TNC OFF then ON again.
RESTART does not cause a reset of the parameters in bbRAM. See
also the RESET command.
RETRY n Default: 10
Display Group: L
Parameter:
n 0 - 15, specifying the maximum number of packet
retries.
The AX.25 protocol allows for retries, i.e., retransmission of
frames that are not acknowledged. Frames are re-transmitted n
times before the operation is aborted. The time between retries
is specified by the command FRACK. A value of 0 for n specifies
an infinite number of retries. If the number of retries exceeds
n, the TNC will go to the disconnected state (with an informative
message if not in Transparent Mode). See also the FRACK command.
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RXBLOCK ON|OFF Default: OFF
Display Group: A
Parameters:
ON The TNC will send data to the terminal in RXBLOCK
format.
OFF The TNC will send data to the terminal in standard
format.
RXBLOCK is designed for automated operations, such as packet
bulletin board stations. It is intended to help such systems
discriminate between data received from the connected station and
TNC-generated messages.
Correct operation of RXBLOCK is dependent on the AWLEN parameter
being set to 8 (bits) since the character FF hex marks the
beginning of a received data unit header.
When RXBLOCK is on, data from other stations will be sent from
the TNC in the following format:
prefix $FF ::= A character with all 8 bits set
length L0 ::= The high order length of the data,
length, and pid fields logically ORed
with the value $F0
L1 ::= The low order length of the data, length,
and pid fields
pid PID ::= The Protocol IDentifier byte received for
the following data field
data DATA ::=[Optional], variable length data
For best operation it is suggested that parameters like AUTOLF,
MFILTER, etc. be set OFF in order to prevent uncertainties in the
size of the data field.
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RXCAL
Display Group: NONE
RXCAL is an immediate command. It is used for precise alignment
of the demodulator. Briefly, after the modulator tones are set
using the normal CALIBRATE routines, analog loopback is entered
and RXCAL issued. You then tune the demodulator until the CON
and STA LEDs are both lit, or slowly alternate. See the section
Modem Calibration using CAL and RXCAL for details on using this
command with a TAPR TNC 2.
SCREENLN n Default: 0
Display Group: A
Parameters:
n 0 - 255, specifying the screen or platen width, in
characters, of the terminal.
This value is used to format terminal output. A <CR> <LF>
sequence is sent to the terminal at the end of a line in Command
and Converse Modes when n characters have been printed. A value
of zero inhibits this action.
If your computer automatically formats output lines, you should
set SCREENLN 0 to avoid a conflict between the two line formats.
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SENDPAC n Default: $0D <CR>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command selects the character that will force a packet to be
sent in Converse Mode. The parameter n is the ASCII code for the
character you want to type in order to force your input to be
packetized and queued for transmission. You can enter the code
in either hex or decimal.
For ordinary conversation, you will probably set SENDPAC $0D and
CR ON. This causes packets to be set at natural intervals, and
causes the <CR> to be included in the packet.
If you have set CPACTIME ON, you will probably set SENDPAC to
some value not ordinarily used (say, <CTRL-A>), and set CR OFF.
This will allow you to force packets to be sent, but will not
result in extra <CR> characters being transmitted in the text.
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SLOTS n Default: 3
Display Group: L
Parameters:
n 0-127
SLOTS specifies the number of "slots" from which to choose when
deciding to access the channel. For example, SLOTS 3 means there
are three slots, each having a probability of 1/3 to be selected.
Each slot is DEADTIME long. If SLOTS 0 is chosen, the TNC will
act as if SLOTS 1 had been selected.
Other implementations of this idea of channel access use
"PERSISTENCE" to decide the probability of channel access when
the channel is clear and "PPERSISTENCE" to enable or disable this
feature.
A low value means a greater chance of attempting to send data
when the channel is clear, and a higher value means less chance.
Normal AX.25 practice is to have every station jump on the
channel when it goes clear, virtually assuring collisions and
retries.
SLOTS and its relation to the more common PPERSISTENCE and
PERSISTENCE commands are given below:
SLOTS PPERSISTENCE PERSISTENCE Probability to XMIT
1 OFF 255 Jump on = 100%
2 ON 127 50%
3 ON 85 33%
4 ON 63 25%
5 ON 51 20%
and so forth.
A typical value would be 2 or 3 for a channel with a few other
users and 5 to 7 for a fairly busy channel. Higher values than
about 10 imply the channel is too busy and other frequencies
should be used if available.
Note: SLOTS is independent of ACKPRIOR.
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START n Default: $11 <CTRL-Q>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command selects the User Restart character, which is used to
restart output from the TNC to the terminal after it has been
halted by typing the User Stop character. You can enter the code
in either hex or decimal.
The User Stop character is set by the STOP command.
If the User Restart and User Stop characters are set to $00,
software flow control to the TNC is disabled, and the TNC will
only respond to hardware flow control (CTS).
If the same character is used for both the User Restart and User
Stop characters the TNC will alternately start and stop
transmission upon receipt of the character.
STATUS
Display Group: NONE
STATUS is an immediate command. It returns the acknowledged
status of the current outgoing packet link buffer. If all
outgoing packets are acknowledged, STATUS returns 'No Outstanding
packets', otherwise it returns the 'Outstanding packets' message.
Note that this command works independently of the RS-232
flow-control state of the TNC.
This command may be useful for special applications, like if you
can't see the STATUS LED on the TNC, or you want your computer to
watch the status...
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STOP n Default: $13 <CTRL-S>
Display Group: C
Parameters:
n 0 - $7F, specifying an ASCII character code.
This command selects the User Stop character, which is used to
stop output from the TNC to the terminal. You can enter the code
in either hex or decimal. This is the character you will type to
halt the TNC's typing so that you can read text before it scrolls
off your display.
Output is restarted with the User Restart character, which is set
by the START command.
If the User Restart and User Stop characters are set to $00,
software flow control to the TNC is disabled, and the TNC will
only respond to hardware flow control (CTS).
If the same character is used for both the User Restart and User
Stop characters the TNC will alternately start and stop
transmission upon receipt of the character.
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STREAMCA ON|OFF Default: OFF
Display Group: C
Parameters:
ON Callsign of other station displayed.
OFF Callsign of other station not displayed.
This command is used to enable the display of the connected-to
station after the stream identifier. This is particularly useful
when operating with multiple connections allowed. It is somewhat
analogous to the use of MRPT to show digipeat paths when mon-
itoring.
In the example below, the characters inserted by enabling STREAM-
CAll are shown in bold face type.
|A:K4NTA:hi howie
hello ted how goes it?
|B:WA7GXD:*** CONNECTED to WA7GXD
|Bmust be a dx record. ge lyle
|Aunreal ted! fl-az no digis!
|B:WA7GXD:big band opening...ge
etc.
The same sequence with STREAMCAll OFF would look like the fol-
lowing:
|Ahi howie
hello ted how goes it?
|B*** CONNECTED to WA7GXD
|Bmust be a dx record. ge lyle
|Aunreal ted! fl-az no digis!
|Bbig band opening...ge
etc.
Thus, what would have looked like "|B" now appears as
"|B:<callsign>:". This option is very useful for human operators
trying to operate multiple simultaneous connections. It is pro-
bably less useful for "host" operations.
Note that, in the first example, the STREAMSWitch characters "|A"
and "|B" with no ":" after them were entered by the operator of
the TNC to switch streams for his multiple-connect QSO(s). If
you intend to operate multiple connections (as opposed to having
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your "host" computer operate multiple connections), use of this
option is recommended.
STREAMDB ON|OFF Default: OFF
Display Group: C
Parameters:
ON Double all received STREAMSWitch characters.
OFF Do not "double" received STREAMSWitch characters.
This command is used to display received STREAMSWitch characters
by "doubling" them. The example below illustrates this action.
With STREAMDB on, and STREAMSWitch set to "|", the following
might be displayed from your TNC:
|| this is a test.
In this case the sending station actually transmitted
| this is a test.
The same frame received with STREAMDB OFF would be displayed as:
| this is a test.
When operating with multiple connections, this is useful for
differentiating between STREAMSWitch characters received from
other stations and STREAMSWitch characters internally generated
by your TNC.
Note: The STREAMSWitch character must NOT be one of the stream
letters (A - J) for this command to function properly.
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STREAMSW n Default: $7C < | >
Display Group: C
Parameters:
n 0 - $FF, usually specifying an ASCII character
code.
This command selects the character used by both the TNC and the
user that a new "stream" (connection channel) is being addressed.
The character can be PASSed in CONVERS mode. It is always ig-
nored as a user-initiated stream switch in TRANSPARENT mode, and
flows through as data. This means that the outgoing stream can
not be changed while "on line" in TRANSPARENT mode (you must
escape to COMMAND mode to switch streams).
For further usage of this character, see the STREAMDBL and
STREAMCA commands.
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TRACE ON|OFF Default: OFF
Display Group: L
Parameters:
ON Trace mode is enabled.
OFF Trace mode is disabled.
This command is used to enable the protocol debugging function.
When TRACE is ON, all received frames will be displayed in their
entirety, including all header information. In normal operation
you will probably never need this function; however, if you need
to report an apparent software bug, you may be asked to provide
trace information if possible.
A trace display will appear in four columns on an 80-column
display. Following is an example trace display. For comparison,
the frame shown in the trace example would be monitored as
follows:
The byte column shows the offset into the packet of the beginning
byte of the line. The hex display column shows the next 16 bytes
of the packet, exactly as received, in standard hex format. The
shifted ASCII column attempts to decode the high order seven bits
of each byte as an ASCII character code. The ASCII column
attempts to decode the low order seven bits of each byte as an
ASCII character code. In a standard AX.25 packet, the callsign
address field will be displayed correctly in the shifted ASCII
column. A text message will be displayed correctly in the ASCII
column. Non-printing characters and control characters are
displayed in both ASCII fields as ".". You can examine the hex
display field to see the contents of the sub-station ID byte and
the control bytes used by the protocol. Protocol details are
discussed in Chapter 9.
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TRANS
Display Group: NONE
This is an immediate command. It causes the TNC to exit from
Command Mode into Transparent Mode. The current link state is
not affected.
Transparent Mode is primarily useful for computer communications.
In this mode, the "human interface" features such as input
editing capability, echoing of input characters, and type-in flow
control are disabled. You may find Transparent Mode useful for
computer Bulletin Board operations or for transferring non-text
files. See the discussion of Transparent Mode in Chapter 5.
TRFLOW ON|OFF Default: OFF
Display Group: A
Parameters:
ON Software flow control can be enabled for the computer
or terminal in Transparent Mode.
OFF Software flow control is disabled for the computer or
terminal in Transparent Mode.
If TRFLOW is ON, the settings of START and STOP are used to
determine the type of flow control used in Transparent Mode. If
TRFLOW is OFF, only hardware flow control is available to the
computer and all characters received by the TNC are transmitted
as data. If START and STOP are set to $00, disabling the User
Stop and User Restart characters, hardware flow control must
always be used by the computer.
If TRFLOW is ON, and START and STOP are non-zero, software flow
control is enabled for the user's computer or terminal. The TNC
will respond to the User's Restart and User's Stop characters
(set by START and STOP) while remaining transparent to all other
characters from the terminal. Unless TXFLOW is also ON, only
hardware flow control is available to the TNC to control output
from the terminal.
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TRIES n Default: None
Display Group: L
Parameters:
n 0 -15, specifying the current RETRY level on the
currently selected input stream.
This command is used to retrieve (or force) the count of "tries"
on the currently selected input stream.
When used with no argument: if the TNC has an outstanding unack-
nowledged frame, it will return the current number of tries; if
the TNC has no outstanding unacknowledged frames, it will return
the number of tries required to obtain an acknowledgment for the
previous frame.
Note: If RETRY is set to 0, the value returned by issuing a
TRIES command will always be 0.
This command is useful for obtaining statistics on the perfor-
mance of a given path or channel. It should be especially useful
for automatic optimizing of such parameters as PACLEN and MAX-
FRAME by computer-operated stations, such as automatic message
forwarding stations using less-than-optimum paths (noisy HF or
satellite channels, for example).
When used with an argument, TRIES will force the "tries" counter
to the entered value. Use of this command to force a new count
of tries is not recommended.
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TXDELAY n Default: 33
Display Group: T
Parameters:
n 0 - 120, specifying 10 ms intervals.
This value tells the TNC how long to wait after keying up the
transmitter before sending data. Some startup time is required
by all transmitters to put a signal on the air; some need more,
some need less. In general, crystal controlled rigs with diode
antenna switching don't need much time, synthesized rigs need
time for PLL lockup, and rigs with mechanical T/R relays will
need time for physical relay movement. The correct value for a
particular rig should be determined by experimentation. The
proper setting of this value may also be affected by the
requirements of the station you are communicating with. In
general, TXDELAY should be set to the same value as DEADTIME when
ACKPRIOR is ON.
A TAPR TNC 1 running version 3.x firmware interprets n in 40 ms
intervals. The value of TXDELAY on TNC 2 will thus be 4 times
the value used by a TNC 1 to give the same delay time.
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TXDELAYC n Default: 2
Display Group: T
Parameters:
n 0-120 specifying additional transmit delay time
added to TXdelay in terms of CHARACTER TIME at the
current radio port data rate. Flags will be sent
during this time, so a value of 1 is required as a
minimum.
TXDELAYC is used to fine-tune transmit delay after a transmit
command is issued and before data is sent. Used in conjunction
with TXDELAY, it allows a link to be set for maximum performance.
TXDELAY should be used to account for the time it takes the radio
(the slower of this TNC's radio and the remote TNC's radio) to
switch between receive and transmit and allow the receiving
unit's data carrier detect (DCD) circuitry to respond. "0" bytes
are sent to allow the remote TNC to synchronize to the data
stream sent during TXDELAY.
TXDELAYC then sends flags to start the frame. If TXDELAYC 0 is
selected, the TNC will act as if TXDELAYC 1 had been chosen.
With this method of keying up, a user may operate at various HDLC
data rates without having to reset TXDELAY if the same radios are
used. The summation of TXDELAY and TXDELAYC will automatically
adjust the keyup time for the varying rates.
TXDIDDLE ON|OFF Default: ON
The TNC sends NRZI 0s during TXDELAY/TXDELAYC intervals if TXDID-
DLE is ON, and 7EH flags when it is OFF. TXDIDDLE should be kept
ON unless you are certain the TNCs in your network require
lengthy flagging intervals.
A few 1.1.7 users (TXDIDDLE was forced to ON in 1.1.7) reported
problems with other TNCs that require flags during TXDELAY/TXDE-
LAYC for carrier detection. Now when this problem crops up, the
user has the ability to turn TXDIDDLE OFF and restore
connectivity.
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TXFLOW ON|OFF Default: OFF
Display Group: A
Parameters:
ON Software flow control can be enabled for the TNC in
Transparent Mode.
OFF Software flow control is disabled for the TNC in
Transparent Mode.
If TXFLOW is ON, the setting of XFLOW is used to determine the
type of flow control used in Transparent Mode. If TXFLOW is OFF,
the TNC will use only hardware flow control and all data sent to
the terminal remains fully transparent.
If TXFLOW and XFLOW are ON, the TNC will use the TNC Restart and
TNC Stop characters (set by XON and XOFF) to control input from
the terminal. Unless TRFLOW is also ON, only hardware flow
control is available to the computer or terminal to control
output from the TNC.
Note that if the TNC Restart and TNC Stop characters are set to
$00, hardware flow control will always be selected regardless of
the setting of TXFLOW.
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TXUIFRAM ON|OFF Default: OFF
Display Group: L
Parameters:
ON The TNC will "flush its buffers" to the radio port upon
loss of a connection.
OFF The TNC will only send BEACON and ID frames as
unconnected (UI) frames. It will discard information
in its buffers upon loss of a connection.
This command determines whether the TNC will transmit most
unconnected information packets.
Setting TXUIFRAMe OFF will prevent all but BEACON and ID
unconnected ("UI") frames from being originated and transmitted.
This is most useful for BBS and other stations which tend to
leave unacknowledged data in the TNC transmit buffer when a
connection is lost. The normal behavior of a TNC would send the
buffered data as "UI" frames, adding to channel congestion.
The behavior with TXUIframe OFF serves to reduce channel
congestion because the now-useless data is never sent.
Note: TXUIFRAM has no effect on the digipeating of UI frames.
It only affects frames being originated at this station.
UNPROTO call1 [VIA call2[,call3...,call9]] Default: "CQ"
Display Group: I
Parameters:
call1 Callsign to be placed in the TO address field.
call 2 - 9 Optional digipeater call list, up to eight calls.
This command is used to set the digipeat and destination address
fields of packets sent in the unconnected (unprotocol) mode.
Unconnected packets are sent as unsequenced I (UI) frames with
the destination and digipeat fields taken from call1 through
call9 options. When no destination is specified, unconnected
packets are sent to CQ. Unconnected packets sent from other TNCs
can be monitored by setting MONITOR ON and setting BUDLIST and
LCALLS appropriately. The digipeater list is also used for
BEACON packets (which are sent to destination address BEACON).
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USERS n Default: 1
Display Group: L
Parameters:
n 0 - 10, specifying the number of active connec-
tions that may be established to this TNC by other
TNCs.
USERS affects only the manner in which incoming connect requests
are handled, and has no effect on the number or handling of
connections you may initiate with this TNC.
For example,
USERS 0 allows incoming connections on any free stream
USERS 1 allows incoming connections on stream A only
USERS 2 allows incoming connections on streams A & B
USERS 3 allows incoming connections on streams A, B & C
and so on through USERS 10.
XFLOW ON|OFF Default: ON
Display Group: A
Parameters:
ON XON/XOFF flow control is enabled.
OFF XON/XOFF flow control is disabled and hardware flow
control is enabled.
If XFLOW is ON, the computer or terminal is assumed to respond to
the TNC Restart and TNC Stop characters set by XON and XOFF. If
XFLOW is OFF, the TNC will communicate flow control commands via
RTS.
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XMITOK ON|OFF Default: ON
Display Group: L
Parameters:
ON Transmit functions are enabled.
OFF Transmit functions are disabled.
When XMITOK is OFF, transmitting is inhibited. All other
functions of the TNC remain the same. In other words, the TNC
generates and sends packets as requested, but does not key the
radio PTT line.
You might use this command to insure that your TNC does not
transmit in your absence if you leave it operating to monitor
packet activity. This command can also be used for testing using
loopback or direct wire connections when PTT operation is not
relevant.
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XOFF n Default: $13 <CTRL-S>
Display Group: C
Parameters:
n 0 to $7F, specifying an ASCII character code.
This command selects the TNC Stop character, which is sent from
the TNC to the computer or terminal to stop input from that
device. You can enter the code in either hex or decimal.
This character would ordinarily be set to <CTRL-S> for computer
data transfers. If you are operating your station in a Converse
Mode and there is some chance that you might fill up the TNC's
buffers, you might set this character to <CTRL-G> ($07), which
rings a bell on many terminals.
XON n Default: $11 <CTRL-Q>
Display Group: C
Parameters:
n 0 to $7F, specifying an ASCII character code.
This command selects the TNC Restart character, which is sent
from the TNC to the computer or terminal to restart input from
that device. You can enter the code in either hex or decimal.
This character would ordinarily be set to <CTRL-Q> for computer
data transfers. If you are operating your station in Converse
Mode, and there is some chance that you might fill up the TNC's
buffers, you might set this character to <CTRL-G> ($07), which
rings a bell on many terminals.
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Messages
This section describes the messages your TNC may produce and the
circumstances under which they will appear.
General Messages
|A
Tucson Amateur Packet Radio TNC 2
AX.25 Level 2 Version 2.0
Release n.n.n mm/dd/yy - nnK RAM
Checksum $xx
cmd:
This is the sign-on message that appears when you turn on your
TNC or when you issue the RESET command. The release number will
be updated whenever the firmware is changed. The checksum is a
hex number which you can compare against the correct checksum
given for the firmware version you are using.
NOTE: The |A may display as a vertical bar and any capital
letter from "A" through "J".
bbRAM loaded with defaults
This message appears along with the sign-on message above if the
battery backed-up RAM checksum verification fails at power-on
time, causing the TNC to load the default parameters from ROM.
(This will be the case the first time you turn on your TNC.)
This message also appears if the TNC loads the defaults in
response to the RESET command.
cmd:
This is the Command Mode prompt. When this prompt appears, the
TNC is waiting for you to issue a command. Anything you type
after this prompt will be interpreted as a command to the TNC.
If a monitored packet has been displayed, the prompt may not be
visible, even though you are in Command Mode. You can type the
redisplay-line character (set by REDISPLA) to retype the prompt.
was
Whenever you change the setting of one of the TNC's parameters,
the previous value will be displayed. This confirms that the TNC
properly interpreted your command, and reminds you of what you
have done.
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too many packets outstanding
This message will appear in response to a CONVERS or TRANS
command, if you have previously entered packet data filling the
outgoing buffer in Converse Mode or Transparent Mode and then
returned to Command Mode. You will be allowed to exit Command
Mode after some of the packets have been successfully
transmitted.
Command Mode Error Messages
If you make a mistake typing a command to the TNC, an error
message will be printed. You may see any of the following
messages depending on the type of error you have made.
?bad
You typed a command correctly, but the remainder of the command
line couldn't be interpreted.
?call
You entered a callsign argument that does not meet the TNC's
requirements for callsigns. A callsign may be any string of
numbers and letters, including at least one letter. Punctuation
and spaces are not allowed. The sub-station ID, if given, must
be a (decimal) number from 0 to 15, separated from the call by a
hyphen.
?clock not set
This message appears if you give the command DAYTIME to display
the date and time without having previously set the clock.
DAYTIME sets the clock if it is given with the daytime
parameters, and displays the date and time if it is given without
parameters.
?EH
The first word you typed is not a command or a command
abbreviation.
?not enough
You didn't give enough arguments for a command that expects
several parameters.
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?not while connected
You attempted to change MYCALL or AX25L2V2 while in a connected
or connecting state.
?not while disconnected
You attempted to perform an operation that can only be done while
connected. This message may appear when issuing a RECONNECT or
CONPERM command.
?already connected to that station
The multi-connect software will not permit you to connect to the
same station using multiple streams.
?range
A numeric argument for a command was too large.
?too long
You entered too long a command line, and the line was ignored.
This might happen, for example, if you try to enter too long a
message with BTEXT or CTEXT. If you get this message, the
previous text entry was not changed.
?too many
You gave too many arguments for a command that expects
several parameters. For example, MFILTER can have up to 4
arguments.
cmd:MFILTER $1B,$0C,$1A,$03,$07
?too many
?VIA
This message appears if you attempt to enter more than one
callsign for the CONNECT or UNPROTO commands without the VIA
keyword.
Link Status Messages
These messages inform you of the status of AX.25 connections your
TNC may be involved in. You can always interrogate the link
status by giving the CONNECT command without parameters. If you
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attempt a connection when your TNC is not in the disconnected
state, the TNC will display the link status but will take no
other action. The following messages appear in response to the
CONNECT command.
Link state is: CONNECTED to call1
[VIA call2[,call3...,call9]]
This display shows the station your TNC is connected to and the
digipeater route if any. The callsign sequence is the same
sequence you would enter to initiate the connection.
*** LINK OUT OF ORDER, possible data loss
[optional daytime stamp]
This message is issued upon failure of a CONPERMed link.
Link state is: DISCONNECTED
No connection currently exists. You may issue the CONNECT
command to initiate a connection.
Link state is: CONNECT in progress
You have issued a connect request, but the acknowledgment from
the other station has not been received. If you issue a DISCONNE
command, the connect process will be aborted.
Link state is: DISCONNECT in progress
You have issued a disconnect request, but the acknowledgment from
the other station has not been received. If you issue a second
DISCONNE command, the TNC will go immediately to the disconnected
state.
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Tucson Amateur Packet Radio TNC 2 System Manual
Link state is: FRMR in progress
The TNC is connected but a protocol error has occurred. This
should never happen when two TAPR TNCs are connected. An
improper implementation of the AX.25 protocol could cause this
state to be entered. The TNC will attempt to re-synchronize
frame numbers with the TNC on the other end, although a
disconnect may result. Connects are not legal in this state, and
a disconnect command will start the disconnect process.
The TNC will inform you whenever the link status changes. The
link status may change in response to a command you give the TNC
(CONNECT or DISCONNE), a connect or disconnect request packet
from another station, a disconnect due to the retry count being
exceeded, an automatic time-out disconnect (CHECK), or a protocol
error.
*** CONNECTED to: call1 [VIA call2[,call3...,call9]]
This message appears when the TNC goes from the "disconnected" or
"connect in progress" state to the connected state. The
connection may be a result of a CONNECT command you issued, or of
a connect request packet received from another station.
This message indicates that the TNC has received a connect
request from another station which it has not accepted. This can
happen if you have set CONOK OFF or if you are already connected
to another station. When the TNC types this message it also
sends a DM packet (busy signal) to the station that initiated the
connect request. If the TNC rejects a connect request because
you have set CONOK OFF, you can issue your own request to the
station that called.
*** DISCONNECTED
This message is displayed whenever the TNC goes to the
disconnected state from any other link state. This message may
be preceded by a message explaining the reason for the
disconnect, below.
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*** retry count exceeded
*** DISCONNECTED
This message is given if the disconnect was caused by a retry
failure rather than by a disconnect request from one of the
stations. It will also occur if you issue two (2) DISCONNE
commands before the remote TNC responds to the first one.
*** <callsign> busy
*** DISCONNECTED
This message indicates that your connect request was rejected by
a DM packet (busy signal) from the other station. A TAPR TNC
will reject a connect request if CONOK is OFF or if it is already
connected to another station (or other stations up to the number
allowed by the USERS command).
frmr frame just sent:
FRMR sent: xxxxxx
The TNC is connected, and a protocol error has occurred. The TNC
has sent a special FRMR packet to attempt to re-synchronize frame
numbers with the TNC on the other end. The string xxxxxx is
replaced with the hex codes for the three bytes sent in the
information part of the FRMR frame. This message will not appear
if your TNC is in Transparent Mode.
FRMR rcvd:
This message is followed by a display of the FRMR packet received
in the trace display format. This format is explained in the
TRACE command entry. This message will not appear if your TNC is
in Transparent Mode.
Health Counters
A number of counters have been added to TNC 2. All of them are
16 bits wide, and are ALWAYS initialized to 0000 on power up or
"RESTART".
These counters are displayed using the HEALTH option of the
DISPLAY command.
o- ASYFRERR: Increases when a character received on the
serial port has a framing error. A large
count may indicate problems in the serial
link between the TNC and the computer or
terminal.
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o- ASYQOVER: Increases when the TNC's async input buffer
overruns. A count greater than 0 indicates
the host computer is not responding properly
to flow control from the TNC. It also means
that data have been lost, so you should take
steps to find out why this is happening and
get it fixed!
o- ASYRXOVR: Increases when the software does not service
the asynchronous receiver in time. Indicates
data from the user to the TNC is being
dropped. This error counter should never
become non-zero under supported data rates.
o- BBFAILED: Counts number of times bbRAM checksum was in
error.
o- DIGISENT: Each frame digipeated by this TNC causes the
counter to increase.
o- HOVRERR: Increases when HDLC receiver is not serviced
rapidly enough and data is lost. This
counter should never increment at any
supported data rate.
o- HUNDRERR: Increases when the HDLC transmitter is not
serviced rapidly enough and frames are
aborted. This counter should never be
non-zero at any supported data rate.
o- RCVDFRMR: Increases when Frame reject frames are
received from a connected station.
o- RCVDIFRA: Increases for each reception of an I frame
from a connectee.
o- RCVDREJ: Increases for each reception of an REJect
frame from a connectee.
o- RCVDRNR: Increases when this TNC receives an RNR
frame. A large count is normal.
o- RCVDSABM: Each received SABM frame addressed to the TNC
causes this counter to be increased by one.
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o- RXABORT: Increases when an aborted frame is received
from the HDLC controller. Large counts are
not uncommon.
o- RXCOUNT: Increases when any frame is received with
good CRC (or any CRC if PASSALL is turned
on).
o- RXERRORS: Increments each time a received frame is
thrown out due to it being too short,
suffering overrun(s), or it having a bad
CRC. Latter occurs only when CRC checking is
enabled (i.e. PASSALL is OFF). This counter
will often increment in the presence of
noise.
o- RXLENERR: Increases when a received frame has a length
error and indicates the TNC has temporarily
become confused. It may be a result of a bug
in the SIO chip and a count above 0 is no
cause for alarm.
o- RXRESYNC: Indicates the number of times the TNC has
recovered from RXLENERR conditions. In
firmware prior to 1.1.7, the TNC would simply
hang until RESTARTed or RESET.
o- SENTFRMR: Increments each time a Frame reject frame is
transmitted.
o- SENTIFRA: Increases by one each time an I frame is
sent.
o- SENTREJ: Whenever a REJect frame is transmitted, this
counter is incremented.
o- SENTRNR: Increases when this TNC sends an RNR frame.
This is useful for determining the
effectiveness of the FIRMRNR routines.
o- TXCOUNT: Incremented whenever a frame is correctly
transmitted.
o- TXQOVFLW: Counts how many times frames were discarded
because the outgoing frame queue was too
small.
o- TXTMO: Counts how many times as the TNC successfully
recovers from HDLC transmitter time-outs.
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Chapter 7 HARDWARE
This chapter includes detailed specifications and a functional
description of the hardware design of the TAPR TNC 2.
TNC 2 Specifications
Processor CMOS Z-80A
Clocks Processor master clock input frequency: 2.4576 MHz
jumper selectable to 4.9152 MHz (requires use of Z80B
CPU, Z80B SIO/0 and 200 nSec EPROMs).
User Port Clock: Switch selectable at 16x baud rate.
Memory All memory in industry-standard JEDEC Byte-Wide
sockets.
Standard complement of ROM: 32k = 1 x 27C256
Standard complement of RAM: 32k = 1 x 43256
ROM complement jumper selectable for 8k-, 16k-, or
32k-byte parts. Memory can be expanded to 32k ROM and
32k RAM using currently available parts.
Serial Z8440 SIO/0 port B configured as UART plus
low-Portpower TTL-to-RS-232C signal level interface.
Baud rates supported: 300, 1200, 2400, 4800 and 9600.
Standard female DB-25S (DCE) RS-232C connector.
Modem Input demodulation filter: MF-10 switched-capaci-
tor filter permits use with unmodified FM trans-
ceivers. Easily configured for SSB via replace-
able DIP headers.
Demodulator: XR2211 PLL demodulator circuit plus
related components to receive up to 1200 baud 1200
Hz/2200 Hz FSK modulation.
Modulator: XR2206 modulator circuit plus related
components to produce 1200 baud 1200 Hz/2200 Hz phase
coherent FSK.
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All important passive modem components mounted on
plug-in DIP headers for ease in substitution and
modification.
Built-in modem calibration system requires no
additional equipment.
An external modem may be attached via a single
connector which completely bypasses the on-board modem.
Support for an external modem tuning indicator is
provided via a separate connector.
bbRAM Non-volatile storage of all important operating
parameters is accomplished by using a battery
backed-up system for the entire 16k bytes of sys-
tem RAM.
Protocol AX.25 Level 2 is supported. Pre-Version 2.0 support is
compatible with earlier TAPR TNCs running 3.x software.
Full support of Version 2.0 protocol is provided. Full
duplex radio link operation is supported.
Operating Command Mode: accepts commands via user port.
Modes
Converse Mode: accepts digital data, transmits and
receives packets, permits terminal editing features
(character delete, line delete, input packet delete,
output packet delete and redisplay input) via special
characters trapped by the TNC. Escape to command mode
via special character or BREAK signal. Optional use of
packet completion timer as in Transparent mode.
Transparent Mode: accepts digital data, transmits
packets via packet completion timer or buffer full
only, and receives packets. No local editing features
permitted. Escape to command mode via specially timed
character sequence or BREAK signal.
Power +10 to +15 volts DC at less than 200 mA.
Required
General Description
The TNC 2 is based on the Zilog Z80 (tm) family of microprocessor
components. All parts used in the TNC should be readily
available to the Radio Amateur.
Major electronic devices in the TNC include a CPU (Central
Processing Unit) for controlling the TNC and a SIO (Serial
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Input/Output) chip for providing serial interface ports to the
on-board modem (which connects to your radio) and to the RS-232C
serial terminal port (which connects to your computer or
terminal).
The TNC also includes two types of memory. ROM (Read Only
Memory) stores the program that tells the TNC how to implement
the AX.25 protocol. Battery backed-up RAM (Random Access Memory)
provides a scratch-pad area for temporary data as well as
non-volatile storage for operating parameters such as your
station call sign. The battery back-up feature enables the TNC
to "remember" these values when power is off so you don't have to
enter them every time you want to operate.
Other integrated circuits are used for functions including clock
oscillator, baud-rate generator, memory-space decoder, power
supply and voltage inverter, clock recovery, transmit watch-dog
timer and modem. Refer to the schematic diagram while reading
the following circuit descriptions.
Detailed Circuit Description
Oscillator
U10a, U10b, U10c, R46, R47, R48, C24, C47, C51, and Y1 provide an
accurate crystal-controlled oscillator for system timing.
R48 forces inverter U10a into its linear region and provides a
load for crystal Y1. C47 provides an adjustable reactive element
to allow the oscillator's frequency to be precisely set (this
precision is not normally required). Inverter U10c buffers the
clock for additional stability before driving additional
dividers.
R46 is used to bias "HCT" logic to the proper levels for best
oscillator operation; it is not necessary if U10 is an "HC" logic
element.
Dividers and Baud-rate Generator
U10e, U10f, U4a, U4b, U1, and SW2 provide clock outputs derived
from the oscillator. Only one of the first 5 switches (terminal
baud rate) and only one of the last 3 switches (RF baud rate)
should be on at any time.
Inverter U10f provides buffering and isolation between the
divide-by-two output of counter U4a and the capacitive load
presented by the CPU (U22) and the SIO (U21). U10f's input may
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Tucson Amateur Packet Radio TNC 2 System Manual
be at 2.4576 MHz (standard) or 4.9152 Mhz via jumper JMP2.
Operation at the faster clock may require the use of higher-speed
parts. Capacitors C59 and C60 are used to slow the edges of the
outputs of U4a, and capacitor C61 is used to slow the edges from
U10f, helping to reduce RFI.
Counter U1 is a multiple-stage divide-by-two circuit that divides
the signal at its input many times. This allows you to select,
via switch SW2, the desired signaling (baud) rate to be used for
your computer or terminal as well as the radio channel baud rate.
The output from counter U1 at pin 12 provides a real-time clock
interval signal for the SIO. During normal operation, the SIO
will be programmed to interrupt the CPU on every transition of
this 600 Hz signal. This interrupt occurs 1200 times a second,
and is used for protocol and calibration timing functions.
Inverter U10e buffers the radio port "16x" baud-rate signal in
case it is routed, via modem disconnect J4 pins 11 and 12, to an
external modem. If this buffer were not included, reflections
from the distant termination might cause counter U1 to generate
count errors.
Counter U4b provides a properly scaled clock for the transmit NRZ
to NRZI encoder (see Serial Interface, below).
CPU Complex
EPROM U23 provides system ROM for program storage. Selector U12a
acts as a ROM decoder, mapping the ROM into the CPU's memory
address space beginning at address 0.
Static RAM U25 provide system RAM for temporary scratch-pad
storage, message buffers, etc. Also, because the RAM is backed
up by a battery and will not lose its contents when the main
power is removed, it is used to provide semi-permanent storage of
user-supplied information (such as your call sign). Selector
U12b acts as a RAM address decoder, with RAM starting at address
8000 hex. JMP12 allows selection of 16k bytes (using 2 x 6264 8k
RAMs) or 32k bytes (using 1 x 43256 32k RAM)) of RAM (only 32k
bytes currently supported by TAPR firmware).
The sections of CMOS switch U13 are used to insure that the RAM
is not selected when main power is removed. This ensures that
the contents of the RAM are not accidentally scrambled as the CPU
loses power; it also ensures that the RAM is in the "power-down"
state for minimum battery power consumption.
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Serial Interface
Serial Input/Output (SIO) device U21 provides two channels of
serial I/O.
The B SIO channel is used for the computer or terminal interface.
Operational amplifier sections U3a, U3b, and U3d act as RS-232C
drivers while Schmitt trigger inverters U9a and U9b act as
RS-232C receivers. These circuits consume less power than
conventional RS-232C drivers and receivers.
The A SIO channel is used for the radio/modem interface and is
normally operated as a full duplex HDLC channel for compatibility
with the AX.25 protocol specification. Latch U5 and ROM U6
provide a "state machine" for recovering the clock from the
received NRZI data. The state machine also converts NRZI data to
NRZ for the SIO. Inverter U9c and flip-flop U11a provide NRZ to
NRZI conversion for the transmit side of the radio channel. This
conversion between NRZ formatted data and NRZI formatted data is
necessary because the AX.25 protocol specification requires NRZI
operation while the SIO is only capable of NRZ. Jumper JMP11 may
be used to bypass the NRZ --> NRZI conversion for use with
external modems, if required.
Watch-dog Timer
Inverters U7c, U7d, U7e, and Q10 provide a "watch-dog" timer on
the transmit key line to ensure that the transmitter does not
remain keyed for more than about 30 seconds if the TNC fails.
This allows you to leave a station (such as a remote digipeater)
on-the-air and unattended without much chance of having a
malfunction "lock up" the packet channel. This also helps ensure
compliance with FCC regulations regarding unattended station
operation.
Jumper JMP4 is provided for testing purposes. When JMP4 is
installed, timing capacitor C31 is shunted, disabling the
watch-dog timer.
Modem
U16, an XR2206, is a Frequency Shift Keying (FSK) modulator that
generates an audio data signal for use by the radio transmitter.
Two tones are used, one for each digital level, and these tones
may be calibrated via trimpots R77 and R78 in conjunction with
the on-board calibration support circuitry and software. When
the transmitter is not being keyed, transistor Q9 is switched on,
thus preventing U16 from producing tones. This allows you to
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Tucson Amateur Packet Radio TNC 2 System Manual
leave a microphone connected to your packet transmitter for voice
operation. DIP header U15 contains the three passive components
which determine the operation of the modulator, as well as R83,
the PTT watch-dog circuit timing resistor.
R76 is used to set the tone output level to the transmitter.
U20, an XR2211, provides a Phase Locked Loop (PLL) FSK
demodulator. It converts the received audio FSK signals into
digital data at standard logic levels. This data is sent to the
state machine clock recovery and NRZI to NRZ format conversion
circuits. R79 is used to calibrate the PLL demodulator's
free-running frequency which is set midway between the FSK tones
being received. This tone is measured by the calibration
software and the output signal produced by U8a and U8b, which is
a frequency doubling shaping circuit. DIP header U19 contains
all passive components which determine the behavior of the
demodulator, with the exception of R73 and C45, the DCD detection
filter. These two components normally do not need to be changed
when the modem is reconfigured. However, in the event the TNC
will be dedicated to 300 baud operation, the DCD detection filter
at U18 pin 3 should have its time constant increased by a factor
of 4, by increasing C45.
U18, an MF-10 switched capacitor filter, provides audio amplitude
and phase equalization to shape the received audio signal before
it goes to the XR2211 demodulator. This equalization helps the
demodulator properly process signals by correcting some of the
distortion that many FM radios introduce. By replacing the
components on DIP header U17, this filter may be configured at
will.
Power Supply
Regulator Q3 and associated components provide a +5 volt
regulated output for the TNC digital logic circuitry. In order
to reduce conducted RFI from the digital power source, series
inductor L1 is provided. Transistor Q4, in conjunction with CMOS
inverters in U14, provides a "power failure" circuit for the
battery-backed RAM chips to ensure that RAM is in the
"power-down" state when the main power is removed. In addition,
this circuit provides the main power-on reset signal via U7f.
Transistors Q5 and Q6 are used to isolate the battery from the +5
volt line when main power is available. R33 protects the lithium
battery from overload conditions and provides a convenient means
of monitoring battery current drain when the TNC is switched off.
JMP5 provides a means of disconnecting the lithium battery for
TNC 2 maintenance.
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U2 and associated components form a charge-pump voltage inverter
which generates an unregulated negative supply for the RS-232C
drivers.
U3c, Q2, CR6 and surrounding components provide a regulated
source of -5 volts for the modem chips.
The modem power sources and ground are isolated from digital
logic switching noise by inductors L2 and L3.
RS-232C Handshaking Protocol
The CTS, DSR and DTR lines of the RS-232C port (J1) are used for
hardware "handshaking" protocol to control the flow of data
between the terminal (DTE) and the TNC (DCE).
The TNC always asserts (makes true) Data Set Ready (DSR) on J1
pin 6 via resistor R16. Thus, whenever the TNC is powered up, it
signals to the terminal connected to J1 that the TNC is "on
line."
The terminal indicates it is ready to receive data from the TNC
by asserting its Data Terminal Ready (DTR) output, J1 pin 20.
The TNC will send data when it has data to send and DTR is
asserted. If the terminal is not ready to receive data, it
should negate (make false) DTR to the TNC. Thus, data flow from
the TNC to the terminal is controlled by the use of the DTR line.
The state of the DTR line is ignored by the software if "software
flow control" is enabled in this direction.
The TNC asserts its Clear To Send (CTS) output, J1 pin 5,
whenever it is ready to receive data from the terminal. If the
TNC's buffers fill, it will negate CTS, signaling the terminal to
stop sending data. The TNC will assert CTS when it is again
ready to receive data from the terminal. Thus, data flow from
the terminal to the TNC is controlled by the use of the CTS line.
The CTS line is always asserted if "software flow control" is
enabled in this direction.
Some serial I/O ports do not implement CTS, DTR and DSR
handshaking. If these pins are not connected at the terminal
end, they will be pulled up (and thus asserted) by resistors at
the TNC end. However, a non-standard serial connector may use
some pins for other purposes, such as supplying power to a
peripheral device, so be sure that your system either implements
the CTS, DTR and DSR handshake or has no connections to these
pins of J1 whatsoever. Note that reference to RS-232C
"compatibility" or the presence of a DB-25 type connector does
not guarantee that you have a full RS-232C serial port!
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The TAPR TNC 2 supports most standard baud rates from 300 through
9600. The port supports standard parity options as well as 7- or
8-bit character lengths. Setting these terminal parameters is
discussed in Chapter 4.
If you want to interface your TNC with a device configured as
DCE, such as a telephone modem or another TNC, a so-called "null
modem" cable may be constructed to interchange the data and
handshake signals. See for example Byte, February, 1981, page
198.
Jumper Functions
The following table lists the function of each jumper on the TNC
2 PC board. The default positions for JMP7, JMP8, JMP9, and
JMP10 are necessary for normal operation to occur.
Jumper Position Function
JMP1 ON !DCD (RS-232C) stays on
OFF (default) !DCD reflects connect status
JMP2 LEFT 4.92 MHz CPU clock
RIGHT (default) 2.46 MHz CPU clock
JMP4 ON disable Tx watch-dog
OFF (default) enable Tx watch-dog
JMP5 ON Lithium battery connected
OFF (default) Lithium battery disconnected
JMP6 ON (default) U23 is type 27256
OFF U23 is not type 27256
JMP7 ON analog loopback mode
OFF (default) normal modem operation
JMP8 ON demodulator enabled
OFF (default) demodulator calibrate
JMP9 TOP calibrate U16 tones
MID calibrate U20 tone
LOW bypass state machine
OFF (default) normal modem operation
JMP10 ON digital loopback mode
OFF (default) normal modem operation
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JMP11 LEFT transmit data NRZ
RIGHT (default) transmit data NRZI
JMP12 TOP 16k RAM (2 x 6264)
BOTTOM (default) 32k RAM (1 x 43256)
Modem Disconnect - J4
The modem disconnect, J4, on the TNC 2 PC board is provided for
using an external modem with the TNC. This allows use of
higher-speed modems, such as 9600 baud, or more sophisticated,
higher-performance modems for OSCAR or other uses.
The following information is primarily for those who wish to
interface external modems to the TNC. Familiarity with modem and
serial data channel terms is assumed.
A physical connector for J4 is not supplied with the TNC. Any
standard 20-pin header for use with IDC cable connectors should
work. Suitable parts are the Ansley 609-2027, the 3M 3428-6202,
etc.
When installing the connector, be sure to line up the marked pin
(pin 1 ) of the header with the lower edge of the PC board
nearest U21. Cut the traces on the bottom of the TNC PC board,
with a sharp knife or Moto-Tool, between each pair of adjacent
pins of J4. To use the on-board modem, install push-on jumper
links across these same pin pairs.
The signals used at connector J4 are at standard TTL interface
levels. A TTL high, or 1, is greater than +2.4 volts but less
than +5.25 volts. A TTL low, or 0, is less than 0.8 volts but
greater than -0.4 volts. DO NOT connect an RS-232C level modem
directly to J4!
NOTE: The modem disconnect is similar, but not identical to
that used in TNC 1. Be very careful about interfacing an
external modem using the same cabling you may have prepared
for use with TNC 1!
The connector pin-outs are as follows.
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Pin 1 Carrier Detect Input
This pin tells the SIO radio port that a valid data carrier
has been detected. It should be pulled high when no carrier
is detected and low when a carrier is present. This line
must be implemented unless the software release notes
indicate otherwise. It is normally jumpered to pin 2 when
the on-board modem is used.
Pin 2 Carrier Detect Output
This pin is an output from the the on-board modem and
satisfies the requirements outlined for pin 1 above. It is
normally jumpered to pin 1 when the on-board modem is used.
Pin 3 SIO Special Interrupt Input
This signal is routed to the radio port DCD input pin on SIO
U21. This signal is normally used during modem calibration.
It may also be used for other purposes; if so, these
functions will be listed in the software release notes.
This pin is normally jumpered to pin 4 when the on-board
modem is used.
Pin 4 SIO Special Interrupt Generator Output
This signal is an output from the on-board modem. It is
normally used for modem calibration only. If it is used for
other functions, they will be stated in the software release
notes. This pin is normally jumpered to pin 3 when the
on-board modem is used.
Pin 5 SIO RTS Output
This signal is used for transmitter activation. The SIO
will pull this output low when the TNC wants to transmit;
otherwise it will remain high. This pin is normally
jumpered to pin 6 when the on-board modem is used.
Pin 6 Transmitter Key Input
This signal is an input to the on-board modem. It activates
the PTT pin of the radio connector via the watch-dog timer.
It should be left high and pulled low only when transmission
is desired. This pin is normally jumpered to pin 5 when the
on-board modem is used.
Pin 7 CONNECT Status Output
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This pin is an output from the SIO. It is normally low and
goes high only when the TNC is in the connected (error-free)
mode with another packet station. Its status is monitored
via the CON LED.
Pin 8 Unacknowledged Packets Pending Status Output
This pin is an output from the SIO. It is normally low and
goes high only when this TNC has unacknowledged packets in
its transmit buffer. Its status is monitored via the STA
LED.
Pin 9 CTS Input
This pin is an input to the SIO. It is high when the
attached modem is not ready to accept data, and low when the
attached modem is ready to accept data. The TNC will not
attempt to send data when this pin is high. This pin is
normally jumpered to pin 10 when the on-board modem is used.
Pin 10 Transmitter Key Input
This pin is physically tied to pin 6, above. It is used in
conjunction with pin 9, above, to allow the TNC to use the
on-board modem whenever the transmitter is activated.
Pin 11 Transmitter Clock (16x) Input
This pin is tied to the NRZ-to-NRZI converter, which expects
a clock signal at 16 times the desired radio port data rate,
e.g., 4800 Hz for 300 baud. This pin is normally jumpered
to pin 12 when the on-board modem is used.
Pin 12 Transmitter Clock (16x) Output
This pin is tied to the radio baud rate switch network. It
provides a clock at 16 times the desired radio port data
rate. This pin is normally jumpered to pin 11 when the
on-board modem is used.
Pin 13 Receive Clock Input
This pin is tied to the SIO receive clock input pin. It
expects a clock at the desired data rate (1200 Hz for 1200
baud), of the proper phase relationship to the received
data. This pin is normally jumpered to pin 14 when the
on-board modem is used.
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Pin 14 Receive Clock Output
This pin is the received data clock signal derived from the
NRZI-to-NRZ state machine. This pin is normally jumpered to
pin 13 when the on-board modem is used.
Pin 15 TNC 2 Ground Reference
This pin ties to the TNC digital ground system, at the SIO.
Pin 16 No Connection
This pin is unused.
Pin 17 Receive Data Input
This pin is the received data input to the NRZI-to-NRZ state
machine. This pin is normally jumpered to pin 18 when the
on-board modem is used.
Pin 18 Receive Data Output
This pin provides receive data from the on-board modem.
This pin is normally jumpered to pin 17 when the on-board
modem is used.
Pin 19 Transmit Data Output
This line is the NRZ or NRZI (depending on the state of
JMP11) data output. This pin is normally jumpered to pin 20
when the on-board modem is used.
Pin 20 Transmit Data Input
This input line accepts data to be be transmitted by the
modem. This pin is normally jumpered to pin 19 when the
on-board modem is used.
If you elect to use an off-board modem, be sure to properly
shield the interconnecting cables for RFI protection.
Tuning Indicator Interface - J3
In order to facilitate communications on HF and OSCAR, the TAPR
TNC 2 includes a connector for attaching a tuning indicator. The
attached unit may range from an oscilloscope to a specialized,
LED-style unit such as the one described in the June 1984 PSR.
Refer to the Exar Application Note referenced in the Bibliography
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for details on functions of the XR2211 signals available on this
connector. A mating connector assembly (shell and 5 pins) may be
obtained from TAPR.
NOTE: Exercise caution when using this connector. Be
especially aware that the TNC 2 modem circuitry is referenced to
+5 volts and -5 volts, not +12 volts and 0 volts!
The connector pinouts are as follows.
Pin 1 -5 volts (Common)
This pin is the on-board modem's analog common. It is not
ground, but -5 volts. This pin should not be used to sink
appreciable currents or excessive noise may be introduced
into the modem, reducing its performance.
Pin 2 Loop Data Filter Output
This pin is connected to the output of the XR2211 PLL data
filter (U20 pin 8). It is a high-impedance source, and care
should be exercised to ensure that no extraneous signals or
low-impedance loads are attached.
Pin 3 Demodulator Reference Voltage
The internal XR2211 data comparator reference voltage is
available on this pin. By comparing this voltage with the signal
on J3 pin 2, correct tuning may be accomplished. As above, this
pin must be carefully shielded from noise, and has a relatively
high internal impedance.
Pin 4 Data Carrier Detect
This pin is an open-collector output that goes near -5 volts
(J3 pin 1) when valid data is not present. It is pulled to
+5 volts by R74 when valid data is detected.
Pin 5 +5 Volts
This pin is a source of +5 volts DC. It should not be used
to source more than a few milliamperes of current or
degradation of the on-board modem's weak-signal performance
may result.
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Chapter 8 TROUBLESHOOTING
WARNING: Never remove or insert an IC with power on!
Your TAPR TNC 2 is a complex piece of electronic equipment.
Servicing must be approached in a logical manner. The best
preparation for troubleshooting is to study the detailed hardware
description in Chapter 7. While it is not possible to present
all possible problems, symptoms and probable cures, this section
of the manual will give direction to troubleshooting based on our
experience.
General Tests
In most cases we have found that careful visual inspection
combined with simple measurements generally reveals the problem.
The most useful single instrument for troubleshooting is a good
DVM that can read AC and DC volts, and can non-destructively test
resistance while the ICs are still in their sockets.
While a number of checks may be made without the aid of an
oscilloscope, you will need one to check signals at various
points on the board if you fail to locate the problem by visual
means or with a meter. Be very careful about shorting pins on
ICs when applying meter or scope probes to the board. It is a
good idea to attach a secure ground lead to the meter or scope,
one that won't accidentally short across components on the board.
A good place to pick up this ground is on the threads of the
screw that mounts regulator Q3 to the printed-circuit board.
Step 1: Power Supply
The first thing to check in any malfunction is the power supply.
Check the power supply levels at the outputs of the voltage
regulators (Q2 and Q3) as well as the output of the inverter
(U2). Are they close to their nominal values? Do all the ICs in
the suspected area have the proper voltage on their power pins?
Is there excessive ripple in any of the DC voltage lines? If so,
check the regulator and associated components, working backwards
toward the input power switch. If the voltage is low, in
conjunction with a hot regulator, suspect a short circuit on the
board.
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If the problem is in the -5 volt supply, work backwards from Q2's
collector (also at U16 pin 1), which should be -5 volts
regulated, to the junction of C9 and CR2 (-V unregulated). If no
voltage appears at -V, then U2 or a related component may be at
fault. Verify that U2 is oscillating by looking at the wave
form at U2 pin 5. If -V is more negative than -7 volts (i.e.,
normal), but the -5 volt regulated voltage is wrong, check the
negative regulator components U3, Q2, R5, R6, R7, R8, CR6, C10,
C11 and C158. If both -V and the -5 volt regulated voltage are
wrong, look for shorts.
Step 2: Obvious Problems
Look for any unusual physical symptoms. Have you installed any
ICs the wrong way? This is almost guaranteed to ruin the IC and
produce a high current through it, detectable by the IC's high
temperature. Are any components discolored? Does something
smell burnt? Do any of the parts seems excessively warm? If you
have never had your fingers on operating digital integrated
circuits before you may erroneously conclude they are too hot
when they are actually operating normally. In general their
normal temperature will be well below the boiling point of water,
but you may not want to keep your finger on them very long.
Step 3: Assembly Problems
Carefully inspect the PC board and component installation. Are
any cold solder joints present? (See the soldering instructions
in the TNC 2 Assembly Manual.) Is a metal screw shorting to the
board anywhere? Are all ICs firmly seated in their sockets? Are
any IC leads tucked under the chip or otherwise bent in such a
manner that they aren't making proper contact with the IC socket?
(This is a very common error, accounting for most problems!)
Inspect the diodes and electrolytic capacitors for proper
installation. Are the diode cathodes pointing the correct way?
Are the negative ends of the electrolytic capacitors pointing the
correct way?
Step 4: Cabling Problems
Inspect the interconnection cabling. Does it work on another
TNC? Has the radio and/or terminal been successfully used on
packet with this or another TNC? Are all the connections tight?
Has the cable frayed or broken?
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Specific Symptoms
While the steps described above may seem obvious, careful
inspection often will point to the problem or give significant
clues as to the probable area of the TNC most suspect. After the
above inspection has been completed and apparent problems dealt
with, it is time to proceed to more specific analysis.
Symptom: TNC appears dead
If the TNC powers up with the PWR, STA, and CON LEDs lit,
followed by STA and CON extinguishing a second or so later, the
processor is working and the software is probably working
correctly. You should suspect the terminal port at this point.
Check all connections and verify the logic levels according to
the terminal interface troubleshooting section in this chapter.
Oscillator and Reset Circuits
If no LEDs wink during the reset cycle the problem may be more
serious. Check to see that the crystal oscillator is working and
that an "M1" signal (154 kHz square wave, 0 to +5 volts) is
coming from U22 pin 27. The crystal oscillator input to the
processor (U22) is pin 6. The input clock should be a (possibly
distorted) square wave signal. Verify that the clock input at
pin 6 of U22 is running at the correct frequency (near 2.4576
MHz).
Verify that the battery backed-up RAM protection circuit, com-
posed of Q4, U14 and associated devices, is going to +5 volts at
U14 pin 6 after input power is applied. This signal enables
normal operation of U24 and U25. There should be a logical low
on the output of U7 pin 12 coincident with the application of
power and lasting for a few hundred milliseconds. Without this
RESET signal, the Z80 probably won't start up properly.
Digital Logic Lines
Remember that all the logic circuits operate at standard TTL
levels (a "low" is less than +0.8 V and a "high" is greater than
+2.4 volts), and all digital inputs and outputs switch between
these two levels. Thus, if you see logic signals switching
between 0 and, say, 1 volt, you can be sure there is a problem
(usually a short). On the other hand, do not mistake switching
transients on digital logic lines for improper operation -- these
show up as ringing and other distortions.
Verify that there is activity on the control bus READ and WRITE
lines, the 3 CHIP-ENABLE lines on the memories (U23-25, pins 20),
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the IOREQ line on U21 pin 36, and the INT line on pin 16. Each
of these lines should show activity, and if any line is quiet
this is a sign of trouble.
Logic lines that show no activity may often be traced to a short
on the pc board, probably due to a solder splash or bridge.
Address and data line shorts may also show up as lack of activity
on the control bus lines, especially the chip selects. Check
each of the 16 address and 8 data lines for activity. Any lines
showing a lack of activity are not operating properly.
If you suspect problems with address or data lines, try removing
all the memory chips. Each address and data line will now show a
distinct pattern. The address lines should be (possibly
distorted) square waves whose periods increase by a factor of two
on successive lines as you step line by line from A0 to A15.
If you decide to use an ohmmeter to check for shorted lines, use
a low voltage/low current test instrument. (Most modern DVMs are
fine for this.) If in doubt, remove any ICs connected to the
lines you are measuring. If you suspect a short, check the high
density areas of the PC board for the problem. In most cases the
short will be found there. It is very unlikely that the PC board
itself will have a short, as every board shipped by TAPR has been
electrically tested for shorts and opens on a commercial
"bed-of-nails" board tester prior to acceptance by TAPR.
Symptom: Modem won't calibrate or key transmitter.
Double check the placement of parts on each DIP header assembly,
measuring resistor values and checking for shorts between
adjacent components and for shorted capacitors.
Calibration of the demodulator's 1700 Hz tone and the modulator's
1200 Hz and 2200 Hz tones is done in software by setting the
specified device to generate the frequency in question and
routing the signal to U21 pin 22 where it causes interrupts to
the Z80 microprocessor. The software calibration routine then
examines the ratio between this interrupt rate and a fixed 1200
Hz interrupt generated by a 600 Hz square wave at U21 pin 29,
then sets the STA and CON LEDs appropriately. In the case of the
1700 Hz tone, it is first passed through U8, acting as a
frequency doubling Schmitt trigger. The input signal to the
Schmitt trigger is a modified sawtooth wave. In the case of the
modulator, the signal presented to U21 pin 22 comes directly from
U16 pin 11, and should be a reasonable square wave.
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Troubleshooting improper calibration amounts to checking for
proper signals at U21 and following up any improper signal. If
the calibration signal is present, but you cannot successfully
calibrate the frequency, you may have an out-of-spec frequency
determining component. Check the values of the appropriate
passive components. Also, check the placement of jumpers! As a
last resort, check the signal frequency with a frequency counter.
Note that, due to frequency jitter while calibrating the
demodulator, the STA and CON LEDs may blink somewhat even when
the 1700 Hz demodulator frequency is correct.
If the transmitter doesn't key, the problem may be in the
watchdog timer, U7, or the PTT transistor, Q10. Check especially
for an open timing capacitor C31 or a bad solder connection
associated with R83 in header U15.
Symptom: Uncopyable transmitted or received packets
If no one seems able to decode your packet transmissions, it is
often the case that your transmitter is being overdriven. The
solution is to reduce the drive level via trimpot R76. Note that
direct connection to typical microphone inputs requires R76 to be
turned to near the minimum signal position to produce
sufficiently low signal levels.
If you are having problems hearing other stations, the
demodulator circuitry associated with U20 may be at fault. Check
the center frequency of the VCO in U20 using the 1700 Hz
calibration procedure. Working in the direction of flow of the
input signal from the radio, verify that it is being passed
through to pin 2 of U20, the input pin. The signal there should
be above 50 mV and below 3 V peak-to-peak for proper operation of
the demodulator. It should be relatively clean, although a few
tens of millivolts of noise is normal, and the signal amplitude
should not change by more than about 25% between high and low
tones.
Terminal Interface Troubleshooting
If you can't get the TNC to sign on and accept data from your
terminal or computer, the problem may be in the RS-232C
interface. The troubleshooting guide below is provided as an aid
to help in resolving problems that may be related to the RS-232C
port.
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Symptom: TNC won't sign on to the terminal.
If you find the TNC won't send data to your terminal, one of the
first things to do is to verify that the DTR line at pin 20 of J1
is not being held low. If the software flow control option is
disabled, the TNC will not send data to the terminal unless its
DTR is asserted. If the terminal does not implement the DTR/CTS
protocol, the DTR/CTS lines (pins 20 and 5 on J1) should remain
unconnected.
Verify that the voltages on the TNC are correct. If the TNC is
in otherwise good condition, check the following pins on the SIO,
U21 (Z8440). Pin 23 should be TTL low (between 0 and +0.8
volts). If this voltage is incorrect, check the voltage at U9
pin 3 and verify that it is greater than +3 volts. If this
voltage is correct, U9 or the traces around it may be bad. If
this is not the problem, disconnect the terminal and check it
again. If this doesn't help, U9, R20 or R22 may be at fault.
If the above checks are ok, observe pin 26 of U21 with an
oscilloscope and cycle the power switch on the TNC. Transitions
on this pin shortly after reset indicate that the TNC is sending
data. Verify that transitions are also present on U3 pin 1. If
these tests fail, the fault could be with U13, R25, R26, U21, J1,
the attached cable or faulty soldering (shorts, cold joints,
etc.)
Symptom: The TNC appears to be signing on but only gibberish is
printed on the terminal.
This indicates that some combination of the data rate (baud
rate), parity option, or number of start and stop bits are not
set the same at the TNC and at the terminal. If possible, set
your terminal to 300 baud. Also verify that the terminal is set
for seven data bits, space parity, and 1 stop bit. These are the
default settings stored in EPROM. For 300 baud, set DIP switch 1
ON (up) and set switches 2 through 5 OFF (down). Be sure only
one of these 5 switches is up! Perform a hard reset by the power
switch OFF then ON (out then in). The sign on message should
appear.
If the TNC still prints gibberish, verify that the terminal is
set to 300 baud and do a power off then on cycle on both the TNC
and terminal. If the message still fails to appear try
troubleshooting with an oscilloscope, looking first at the TXD
pin (pin 26) of U21 (Z8440), then at the x16 baud rate clock
(4800 Hz at 300 baud) on pin 27 of U21.
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Symptom: The TNC signs on OK but won't accept commands.
After the TNC signs on, try giving it a command such as MYCALL or
any other command. If the default settings are in effect, it
will attempt to echo each character you type back to the screen.
If it doesn't echo, be sure that U21 pin 23 has a voltage level
between 0 and +0.8 volts on it. The voltage on U9 pin 3 should
be greater than +3 volts. If these voltages aren't correct, the
fault could be in U9, U21, J1, R20, R22, soldering, or the
interconnecting cable.
If the above checks are OK, use an oscilloscope to verify that
data is present on U21 pin 28 and U9 pin 1 when you strike a key
on your terminal. If not, the data isn't getting from your
terminal to the TNC. Check J1, the cable and U9 again. Finally,
be sure that your terminal actually uses levels less than -3
volts and greater than +3 volts for signal levels. 0 and +5
volts may not work, especially if they are being used direct from
a computer. For example, the Commodore 64 uses TTL levels that
will work only if they are inverted! This is because RS-232C
logic polarity definitions are opposite those of TTL.
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Chapter 9 PACKET RADIO PROTOCOL
Explanation of Protocol
The material in this chapter is intended to supply an overview of
the protocol used to transmit data by the TAPR software.
References are given to more detailed information required by
those wishing to implement these protocols on other hardware.
The material presented below is somewhat tutorial in nature for
those who have not had previous exposure to layered network
protocols, but it presumes some knowledge of general
communications hardware and software. Persons already well
versed in networking may want to skip this chapter and refer to
the primary defining document, Amateur Packet-Radio Link-Layer
Protocol, AX.25 Version 2.0, available from the ARRL, 225 Main
Street, Newington, CT 06111 ($8.00 US, postpaid in the United
States as of this writing).
The TAPR TNC hardware and software architecture is organized in
accordance with the International Standards Organization (ISO)
layered network model. The model describes seven levels and is
officially known as the ISO Reference Model of Open Systems
Interconnection, or simply the ISO Model. The model and many
other interesting topics are discussed in Computer Networks by
Andrew S. Tanenbaum.
The ISO model provides for layered processes, each supplying a
set of services to a higher level process. The TAPR TNC
currently implements the first two layers, the Physical layer and
the Data Link layer.
Physical Layer
The duty of the Physical Layer, layer one, is to provide for the
transmission and reception of data at the bit level. It is
concerned only with how each bit is physically transmitted, i.e.,
voltages on a hardwire line or modem tones on phone or RF links.
The physical layer of the TAPR TNC is described in Chapter 7,
Hardware. It is compatible with the various TNCs currently
available to radio Amateurs. The actual modem interface is
compatible with the Bell 202 standard which is similar to the
CCITT V.23 standard. Any other hardware device which is
compatible with the Bell 202 standard should be compatible with
the TAPR TNC, at least at level one of the ISO reference model.
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Data Link Layer
The duty of the Data Link layer is to supply an error-free stream
of data to higher levels. Since level one simply passes any bits
received to level two and is unaware of the content or overlying
structure of the data, transmission errors are not detectable at
level one. Level two carries the responsibility of detecting and
rejecting bad data, retransmitting rejected data, and detecting
the reception of duplicate data.
Level two accomplishes this task by partitioning data to be
transferred by level one into individual frames, each with its
own error detection field and frame identification fields. The
TAPR TNC supports two versions of a level-two layer, AX.25
version 1.0 and AX.25 version 2.0. Each of these protocols is
based on HDLC, the High-Level Data Link Control protocol defined
by the ISO.
HDLC Frames
Exact knowledge of the format of HDLC frames has been made
largely unnecessary by the advent of LSI and VLSI communications
chips which interface directly with the level one hardware. The
level two software need only supply data to fill in various
fields and the chip takes care of the rest. For completeness
however, an HDLC frame looks like this:
| FLAG | ADDRESS | CONTROL | PID & DATA | FCS | FLAG |
FLAG A unique bit sequence (01111110) used to detect frame boun-
daries. A technique called "bit stuffing" is used to keep all
other parts of the frame from looking like a flag.
ADDRESSA field normally specifying the destination address.
AX.25 uses a minimum of 14 bytes and a maximum of 70 bytes
containing the actual call signs of the source, destination, and
optionally up to eight digipeaters.
CONTROLA byte which identifies the frame type. In the AX.25
protocol, the control field may include frame numbers in one or
two 3-bit fields.
PID A Protocol Identification byte appears as the first
byte of the HDLC DATA field in AX.25 Level Two information
frames, and identifies which Level 3 protocol is implemented, if
any. In the case where no Level 3 protocol is implemented, PID =
$F0.
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DATA This field contains the actual information to be
transferred. This field need not be present. Most frames used
only for link control do not have data fields.
FCS Frame Check Sequence, a 16-bit error detection field.
The communications chip recognizes the opening and closing flags
and passes the address, control, and data (including PID) fields
to the software. The FCS field is a Frame Check Sequence
computed by the transmitting chip and sent with the frame. The
receiving chip recomputes the FCS based on the data received and
rejects any frames in which the received FCS does not match the
computed FCS. There is virtually no chance of an undetected bad
frame using this method. This satisfies the level two task of
bad data detection.
The communications chip used in the TAPR TNC 2 is a Zilog 8440
SIO operating in conjunction with a two-chip "state machine"
which is used to recover the data clock. The transmitted data is
encoded in NRZI form, which encodes a "0" data bit as a
transition in the encoded bit stream and a "1" data bit as no
transition. This, in combination with the "bit-stuffing" which
ensures that no more than five "1"s occur in a row except when
FLAG bytes are being transmitted, guarantees that a logic level
transition occurs at least once every 5 bit times. These
frequent transitions allow the receiver to synchronize its clock
with the transmitter. Other chips which are compatible with the
SIO + "state machine" are the Western Digital 1933/1935 (used on
the TAPR TNC 1, AEA PKT-1, Heathkit HD-4040, etc.), the Intel
8273 (used on the VADCG and Ashby TNCs) and the Zilog 8530 (used
on the Xerox 820 FAD adapter).
While the HDLC format supplied by the communications chips is
used by the AX.25 protocol, there are several other Layer Two
concerns. These are duplicate frame detection, connection and
disconnection of the level two layers on different TNCs, and
buffer overrun avoidance. The AX.25 protocol solves these
problems as described below.
AX.25 Level Two
AX.25 is based on the Balanced Link Access Procedure (LAPB) of
the CCITT X.25 standard. LAPB in turn conforms to the HDLC
standard. Two extensions are made to LAPB in AX.25. These are
the extended address field, and the unnumbered information (UI)
frame. In LAPB, addresses are limited to eight bits, while AX.25
uses from 112 to 560 bits, containing the originator's call sign,
the destination call sign and an optional list of one to eight
digipeater (simplex digital repeater) call signs.
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The UI frame is used to send information bypassing the normal
flow control and acknowledgment protocol. The UI frame is not
acknowledged but can be transmitted at layer two without fear of
disturbing higher layers. It is used for beacon frames, for
automatic identification packets, and for sending information
frames when the TNC is not connected to another TNC, e.g., CQ and
QST activities.
The exact specifications for AX.25 are supplied in the ARRL
publication Amateur Packet-Radio Link-Layer Protocol, AX.25
Version 2.0. The TAPR implementation adheres to this standard
for AX.25 version 2.0. The implementation of version 1.0 is
almost identical to the TAPR TNC 1 version of AX.25 protocol in
software releases 3.x. This provides compatibility with the
majority of Amateur packet radio stations.
The following table lists the frame types used by AX.25 and
describes their purpose. This material is provided to give a
general understanding of the protocol, and is not intended to
replace the published specification. The byte fields are given
as they appear in memory after data is received, i.e., the high
order bit is at the left and the low order bit is at the right.
This is also the format of the display provided by the TRACE
command. Some texts, including the AX.25 protocol specification,
list the bits in the order in which they are transmitted, which
is low order bit first.
The control bytes are presented in hex with "x" used to indicate
four bits which depend on the acknowledge functions the packet is
performing. Usually "x" is a frame number. Frame numbers fit
into three bits and are used to ensure that frames are received
in order and that no frames are missed. Since only three bits
are available, the frame number is counted modulo 8. This is why
the MAXFRAME parameter has a ceiling of 7: no more than seven
frames can be "in flight" (transmitted but unacknowledged) at one
time. A short description of the use of the frames is given
after the table.
63 UA Unnumbered Acknowledge
87 FRMR Frame reject
even I Any frame ending in an even number (in-
cluding $A, $C, and $E) is an information frame.
I This and UI frames are the only frame types containing user
data. The control byte contains this frame's number and the
number of the next frame expected to be received from the
other end of the link.
RR Usually used to acknowledge receipt of an I frame. The RR
function can also be performed by sending an I frame with an
updated "expected next frame number" field.
RNR Used when the buffer space on the receiving side is full.
REJ Used to request retransmission of frames starting from "x".
Missed frames are detected by receiving a frame number
different from that expected.
DM Sent in response to any frame received other than a connect
request (SABM) when the TNC is disconnected. Sent in
response to an SABM whenever the TNC is on the air but can't
connect to the requesting user, e.g., if the TNC is already
connected to someone else or if CONOK is OFF.
SABM Set Asynchronous Balanced Mode - initiates a connect.
DISC Initiates a disconnect.
UA Sent to acknowledge receipt of an SABM or DISC.
FRMR Sent when an abnormal condition occurs, i.e., the control
byte received is undefined or not proper protocol at the
time received.
UI An I frame without a frame number. It is not acknowledged.
Channel Use and Timing Functions
The following discussions mention timing parameters which are set
by various commands. These timing functions are also discussed
in Chapter 5.
An important part of any packet radio protocol is the means by
which many stations make efficient use of an RF channel, achie-
ving maximum throughput with minimum interference. The basis for
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this time domain multiplexing is Carrier-Sensed Multiple Access
(CSMA) with collision detection and collision avoidance.
CSMA means simply that (as every Amateur knows) no station will
transmit if the frequency is in use. The TNC continually moni-
tors for the presence of an audio data carrier on frequency and
transmits only if there is no carrier. (The RF carrier is not
normally detected; however, an input is available on the TNC 2
radio interface connector to allow such an input.) In order to
make detection of a busy channel more reliable, the TNC sends an
audio signal (continuous flags) any time the transmitter is keyed
and a packet is not being sent, as during the transmitter keyup
delay (TXDELAY), or while a slow audio repeater is being keyed
(AXDELAY).
By itself, CSMA is not enough to insure a minimum, or even low,
interference rate, due to the likelihood of simultaneous keyup by
two or more stations. This is where collision detection and
collision avoidance come in. The TNC detects a collision by the
absence of an ACK from the station it is sending to. The
receiving station does not acknowledge the frame that suffered
the collision, since either the FCS was incorrect or the packet
was not heard. There are other possible reasons for non-receipt
of the packet, but the TNC's response is based on the assumption
of a collision.
After transmitting a packet, the TNC waits a "reasonable" length
of time (FRACK) for an acknowledgment. "Reasonable" is
determined by the link activity, frame length, whether the packet
is being digipeated, and other time-related factors. If no ACK
is received, the packet must be re-sent. If the unACKed frame
was lost due to a collision, the assumption is that there is at
least one other packet station out there that also lost a frame
and will probably have exactly the same criterion for deciding
when to retry the transmission as this station is using.
In order to avoid a second collision, the collision avoidance
protocol calls for the stations retrying transmissions to wait a
random time interval after hearing the frequency become clear
before they key their transmitters. There must be enough
different random wait times to provide a reasonable chance of two
or more stations selecting different values. The difference
between adjacent time values must be similar to the keyup time
delay of typical stations on the frequency. This is the time
lapse after a station keys its transmitter before other stations
detect its presence on the channel, and is a function of the
keying circuitry of the transmitter and the signal detection cir-
cuitry of the receiver. We have chosen the random time to be a
multiple (0-15) of the transmitting station's keyup delay
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(TXDELAY). This is reasonable if one's own keyup delay is
similar to that of other stations on the channel.
One other factor must be taken into consideration in optimizing
data throughput. The currently implemented link protocols
provide for relaying (digipeating) of packets. The
acknowledgment procedure for such packets is that the relay
station simply repeats packets without acknowledgment to the
sending station. The receiving station sends its ACK back
through the same digipeaters to the originating station. Since
the digipeated packets are not acknowledged to the digipeater, an
unsuccessful transmission must be retried from scratch by the
originating station. In order to help alleviate the congestion
of the frequency that tends to result when digipeated packets
suffer collisions, the digipeater is given first shot at the
frequency every time it becomesclear. Other stations, instead of
transmitting as soon as they hear the channel clear, must wait a
short time (DWAIT). This restriction applies to all stations
except the digipeater, which is permitted to transmit relayed
packets immediately. This prevents digipeated packets from
suffering collisions except on transmission by the originating
station.
A special time delay (RESPTIME) is used as the minimum wait time
prior to transmitting acknowledgment frames, to prevent TNCs
accepting data at high speed from the asynchronous port from
colliding with acknowledgment frames when fewer than MAXFRAME
packets are outstanding. The receiving TNC will wait long enough
before sending the ACK so that it will hear the data packet which
would have caused the collision, thus avoiding a fairly frequent
source of delay in versions of AX.25 prior to 2.0.
Channel Flow Control
Flow control of data through the link is determined by the rate
at which data is being supplied to a sending TNC and accepted
from a receiving TNC.
A TNC receiving data from the link will send an RNR when the next
I frame successfully received will not fit into the buffer for
output to the serial port.
Whenever a TNC transmitting data received from the serial port
over the link runs out of temporary buffer space, the serial port
will be halted by an XOFF character or CTS signal. In the TNC 2
implementation this happens whenever there are 7 packets built
and less than 210 characters left in the buffer for input from
the serial port.
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When the TNC receiving data from the link clears out its buffers,
it sends an RR to the transmitting TNC. In order to guard
against the possibility of the RR being lost and the link
becoming permanently locked, the transmitting TNC will
periodically re-transmit the packet that provoked the RNR. The
receiving TNC will continue to respond with RNR until it can
accept the packet.
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Appendix A Multi-Connect Survival Guide
This section is a very brief tutorial on the use of the
multiple-connection capability included with this software
release.
Why Multi-Connect?
Multiple connection capability is a powerful addition to your TNC
2. It is very useful for traffic net operation, multi-user
bulletin boards, path checking and so forth.
What is Multi-Connect?
Multiple connection operation is not the same as multi-way
operation. With multiple connect, you may establish several
point-to-point "links" with various stations. Multi-way, which
is not available, would enable multiple stations to be
simultaneously interconnected to each other, with each station
seeing all data passed from any station in the group, error free.
Multiple connection operation is another step on the road to
proper networking, and networking should eventually allow
multi-way operation.
What Commands Set my TNC 2 to Normal Operation?
Your TNC 2 defaults the multi-connect-related commands to the
following parameters:
CONPERM OFF
STREAMCAll OFF
STREAMDouBLe OFF
STREAMSWitch |
USERS 1
This sets up your TNC 2 to act just like a "normal" TNC does that
doesn't support multiple connections. The key to obtaining this
traditional operation is to set USERS 1.
How Do I Invoke Multi-Connect?
If USERS is not 1, you are telling the TNC to allow multiple
connections to your stations from other stations. In addition,
TRANSPARENT mode will operate differently, in that incoming data
will be prefixed with the current STREAMSWitch character and
identifier (such as "|A"). Thus, truly transparent multiple
connection operation is not possible with this software release.
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The STREAMSWitch character, defaulted to "|", should be set to a
character you won't normally use. Note that this character may
be set to a hex value between $80 and $FF. This may allow you to
use 8-bit characters (AWLEN 8) if your terminal or computer is
capable of generating such "characters." This could help prevent
confusion in interpreting incoming data from other stations if
they happen to send data that includes your selected STREAMSWitch
character.
Although not foolproof, enabling STREAMDBL may also help in
sorting out STREAMSWitch characters included in the received data
from a valid stream switches generated by your TNC 2.
STREAMCAll should be especially helpful when manually operating a
station in which you allow multiple connections.
When in CONVERSE mode, you may switch streams by entering the
STREAMSWitch character (default "|"), followed by a stream
identifier ("A" through "J"), followed by the data you wish to
send to the station on that stream. See the example in the
description of STREAMCAll for an illustration of this.
If all this seems a bit confusing, don't worry, it is! The only
way to really understand multiple connect operation is to try it!
Once you have your TNC 2 on-the-air, and have gained confidence
in "normal" packet operation, try setting USERS 2 and get a
couple of friends to connect to you. Play with the commands (you
can't hurt the TNC by issuing commands to it!) and see their
effects.
Happy packeting!
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Appendix B Prioritized Acknowledgment - An Overview
THE IDEA
The idea behind the prioritized acknowledgement (PriACK) protocol
is quite simple. Acknowledgments (ACKs) get priority access to
the channel so that time is not wasted retrying packets that have
already been correctly copied by the remote TNC. In normal AX.25
practice, for a variety of reasons, the ACK is often not received
within the time limit defined by the FRACK (T1) protocol timer.
In fact, because "channel access" methods are not clearly defined
in the AX.25 Level Two Version 2.0 protocol document, the present
protocol is more likely to synchronize collisions with
acknowledgement packets than with any other type of packet!
THE PROBLEM
When a channel becomes clear, if your TNC has something to send,
it will immediately send it. Unfortunately, if anyone else's TNC
has something to send, it will also "jump on" the channel as soon
as it becomes clear. The result is collisions and retries. Only
after a collision does the present protocol suggest using random
backoff. Thus, an acknowledgment to a just-received packet is
almost assured of a collision-and-retry sequence, even thought
the TNC correctly received the packet. This will usually cause
the TNC which is awaiting the ACK to time out and re-send the
data.
To this collision synchronization mechanism, AX.25 Level Two
Version 2.0 adds a propensity to cause even ACKs which are not
from hidden terminals, and thus less susceptible to collision, to
be delayed beyond even generous FRACK timer settings when the
channel gets busy.
Once FRACK times out, even if the ACK finally makes it through
before the retry is sent, the original packet is retried anyway.
This wastes a lot of time which could be better used clearing the
channel of some of the legitimate offered load.
This feature of AX.25 Level Two protocol accounts for much of the
abysmal performance of the currently popular NETROM and THENET
nodes when used with omnidirectional antennas systems.
HOW IT WORKS
PriACK protocol avoids the above problems by giving ACKs priority
access to the channel. It does this in such a way that even ACKs
coming from hidden terminals are usually protected from
collision.
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Standard AX.25 protocol gives a limited version of this priority
access only to digipeated frames through the DWAIT timer.
Ack prioritization works with slotted channel access in the
following way:
1. Response frames (ACKs) are always sent immediately upon
receipt of a valid packet. Ultimately, not even DCD will be
checked for sending an ACK. However, in this release DCD will
still hold an ACK off the channel.
2. Stations queued up to access the channel but waiting for a
channel busy condition (DCD true) to clear, will start a slotted
access procedure only after enough time for a response frame to
clear the channel has transpired (ACKTIME). This is true even if
the TNC waiting to use the channel cannot hear the ACK being
sent.
3. Slot time windows (DEADTIME) are set large enough to ensure
the local TNC will be able to accurately determine if another
detectable station has started transmitting in any slot
preceeding the slot selected by the local TNC. This prevents two
TNCs which have selected adjacent slots from colliding.
As you can see, under this protocol there will never be a
condition where an ACK is delayed from being sent beyond the
FRACK timer limitation. However, the FRACK timer is still active
and must be set to a value that is long enough to allow time for
(MAXFRAME * PACLEN) + ACKWAIT to expire before FRACK does. This
time will depend on the radio and radio channel data rate in use.
The TNC knows that if it doesn't see the ACK immediately when
expected, it is probably never going to see it. (See discussion
of new parameters below for definition of ACKWAIT.)
Forcing a channel access delay for all stations on the channel
which are waiting for a chance to transmit allows ACKs from
hidden terminals to get back to the expecting station. This
clears that traffic from the offered channel load. If the packet
was indeed copied and ACKed, further retrys of the same
information will not be necessary.
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NEW PARAMETERS
There are several new parameters needed for PriACK operation.
See the command description elsewhere in this document for their
meanings and settings.
This timer actually consists of the sum of ACKTIME + DEADTIME.
It represents the time the queued up TNC will wait before
transmitting if it has selected the first slot. This allows time
for a hidden station's ACK to be sent on the channel.
It is split into two timers because it has two unrelated
components. One is related only to the data rate being used on
the channel (ACKTIME). The other is related only to the absolute
time the radios and TNC DCD circuits require to determine that a
transmitter is active after PTT is asserted (DEADTIME).
OTHER RELATED PARAMETERS
Several of the "standard" TNC parameters will affect PriACK
operation. Most of these are parameters in TNCs on the channel
which are not using PriACK.
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FRACK
FRACK must be set correctly in any TNC regardless of protocol.
FRACK should be set to a value which allows time for the TNC to
send its packet and receive the ACK. This value will depend on
the settings being used for PACLEN and the radio port data rate.
This is because, in many TNCs, the FRACK timer starts at the
beginning of the packet rather than at the end! Thus, it is best
to set FRACK to its worst case value for whatever data rate you
are using on the radio port and still allow for MAXFRAME 7 PACLEN
255 packets to be sent and allow other non-PriACK stations to
collide. This way you can make adjustments to PACLEN without
having to worry about interaction with the setting of FRACK.
FRACK should be set to 8 for 1200 baud work and 16 for 300 baud
operation.
RESPTIME
If you are running PriACK on a channel where some of the stations
have long RESPTIME delays, those stations will not be able to
successfully communicate with you after connecting. If you wish
to communicate with these stations you will have to set your
FRACK timer to a number which is longer than the other stations
RESPTIME delay.
RESPTIME should be set to 0 in your TNC when running PriACK.
With proper DCD operation, RESPTIME 0 will work in any event.
DWAIT
DWAIT is ignored when running PriACK. However, when PRiACK is
off, or if you are using a TNC which does not yet have PriACK
capability, DWAIT should be set to DEADTIME, or 33 (330 mSec) for
the default.
TXDELAY
TXDELAY should be set to allow for the slowest radio oin the
channel. It should be the same as DEADTIME and DWAIT. The
default of 33 (330 mSec) is adequate for most work.
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INITIAL PARAMETER SETTINGS SUMMARY
The settings for use at 1200 baud on a VHF FM channel are:
ACKPRIOR ON
SLOTS 3
DEADTIME 33
ACKTIME 14
RESPTIME 0 (If you require a nonzero value for this parameter
in order to prevent ACKing individual packets in a
MAXFRAME greater than 1 blast, your DCD circuit is
not working. Please get it fixed.)
DWAIT 33
MAXFRAME 1-7 depending on channel quality
FRACK 8
The settings to use for 300 baud work on a linear mode HF channel
are:
ACKPRIOR ON
SLOTS 3
DEADTIME 8
ACKTIME 52
DWAIT 8
RESPTIME 0
MAXFRAME 1
FRACK 16
PACLEN 32 to 128 depending on channel quality
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Appendix C Default Locations
The default parameters for the various TNC 2 commands are located
in the 1.1.8 EPROM. The defaults are documented here for those
of you who wish to change them for particular applications (such
as remotely located units, etc.). For release 1.1.8, the
defaults table is found at address 0B98 hex.
NOTE: In future releases of firmware, this location may change.
There is a pointer at address 0055H which contains the location
of the default area in Z80 low-byte/high-byte format.
WARNING! The TNC 2 firmware does not check for valid defaults.
If you program an invalid default (for example, parity 5),
unpredictable results may occur. Be sure you double-check any
defaults you change!
The defaults are listed in the table below. All notes follow the
table.
EPROM Value Meaning Command Notes
Address (Hex)
(Hex)
0BB3 0C 12 CHECK 12*10 Sec Stream E
0BB4 0C 12 CHECK 12*10 Sec Stream F
0BB5 0C 12 CHECK 12*10 Sec Stream G
0BB6 0C 12 CHECK 12*10 Sec Stream H
0BB7 0C 12 CHECK 12*10 Sec Stream I
0BB8 0C 12 CHECK 12*10 Sec Stream J
0BB9 05 5 reserved - must be 5
0BBA 00 0 reserved - must be 0
0BBB 00 0 reserved - must be 0
0BBC 00 0 reserved - must be 0
0BBD 00 0 reserved - must be 0
0BBE 00 0 reserved - must be 0
0BBF 00 0 reserved - must be 0
0BC0 00 0 reserved - must be 0
0BC1 00 0 reserved - must be 0
0BC2 00 0 reserved - must be 0
0BC3 00 0 reserved - must be 0
0BC4 01 1 BEACON EVERY/AFTER*,DEF EVERY
0BC5 00 0 BEACON TIME (0 = never)
0BC6 9C 'N' MYCALL Note 4
0BC7 9E 'O'
0BC8 86 'C'
0BC9 82 'A'
0BCA 98 'L'
0BCB 98 'L'
0BCC 60 SSID 0
0BCD 00 0 must be 0 - end of callsign string
0BCE 40 ' ' MYALIAS Note 4
0BCF 40 ' '
0BD0 40 ' '
0BD1 40 ' '
0BD2 40 ' '
0BD3 40 ' '
0BD4 60 SSID 0
0BD5 00 0 must be 0 - end of callsign string
0BD6 08 8 FRACK 8*1 Sec
0BD7 80 128 PACLEN
0BD8 0A 10 RETRY
0BD9 00 0 reserved - must be 0
0BDA 04 4 MAXFRAME
0BDB 07 7 AWLEN - must be 7 or 8
0BDC 03 3 PARITY EVEN Note 5
0BDD 00 0 AXDELAY
0BDE 02 2 TXDELAYC
0BDF 03 3 SLOTS
0BE0 7C '|' STREAMSW Character
0BE1 01 1 USERS
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EPROM Value Meaning Command Notes
Address (Hex)
(Hex)
0BE2 0D ^M SENDPAC Character
0BE3 18 ^X CANLINE Character
0BE4 19 ^Y CANPAC Character
0BE5 03 ^C COMMAND Character
0BE6 08 ^H DELETE Character
0BE7 16 ^V PASS Character
0BE8 12 ^R REDISPLAY Character
0BE9 13 ^S STOP Character
0BEA 11 ^Q START Character
0BEB 13 ^S XOFF Character
0BEC 11 ^Q XON Character
0BED 00 0 NULLS
0BEE 00 0 SCREENLN
0BEF 0000 0 CLKADJ
0BF1 00 0 TAPRLATCH
0BF2 00 0 MFILTER 1st Parameter
0BF3 00 0 MFILTER 2nd Parameter
0BF4 00 0 MFILTER 3rd Parameter
0BF5 00 0 MFILTER 4th Parameter
0BF6 00 0 MFILTER 5th Parameter
0BF7 09 CMDS3 Note 7
0BF8 6A CMDS4 Note 8
0BF9 44 CMDS5 Note 9
0BFA 00 CMDS6 Note 10
0BFB 20 CMDS7 Note 11
0BFC 3D CMDS8 Note 12
0BFD 02 CMDS9 Note 13
0BFE 46 CMDS10 Note 14
0BFF 1F CMDS11 Note 15
0C00 60 CMDS12 Note 16
0C01 B8 CMDS13 Note 17
0C02 60 CMDS14 Note 18
0C03 00 0 MYDLCNUM
0C04 FE 254 DEFLTDLC
0C05 00 0 Last Beacon Time - default to 0
0C06 8D reserved - must be 08DH
0C07 00 0 reserved - must be 0
0C08 00 0 reserved - must be 0
0C09 00 0 reserved - must be 0
0C0A 00 0 reserved - must be 0
0C0B 00 0 reserved - must be 0
0C0C 00 0 reserved - must be 0
0C0D 00 0 reserved - must be 0
0C0E 00 0 reserved - must be 0
0C0F 00 0 reserved - must be 0
0C10 00 0 reserved - must be 0
0C11 00 0 reserved - must be 0
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EPROM Value Meaning Command Notes
Address (Hex)
(Hex)
0C12 00 0 reserved - must be 0
0C13 00 0 reserved - must be 0
0C14 00 0 reserved - must be 0
0C15 00 0 reserved - must be 0
0C16 00 0 reserved - must be 0
0C17 00 0 reserved - must be 0
0C18 86 'C' UNPROTO CALL See Note 4
0C19 A2 'Q'
0C1A 40 ' '
0C1B 40 ' '
0C1C 40 ' '
0C1D 40 ' '
0C1E 60 SSID 0
0C1F 00 0 must be 0 - end of callsign string
0C25 MFLAGS Note 19
0C26 DFLAGS Note 20
0C27 CONFLAG Note 21
0C28 ENTRYSTA Note 22
0C29 ENT2 Note 23
NOTES
Note 1
This is the timer which, when it is exceeded, increments the
TXTIMEOUT Health counter.
Note 2
TODVAL specifies the number of "ticks" the DAYTIME clock
increments each second. It should always be set to 1.
Note 3
IDVAL is not otherwise settable. It specifies the number of
10-second intervals which elapse between IDs when HID is ON.
Note 4
Callsigns are encoded per the AX.25 standard document. A
callsign consists of six (6) numbers and letters. The
letters must be upper case and, if the callsign is less than
six (6) elements long, must be right-filled with blanks.
The ASCII values corresponding to the letters and numbers
must be left-shifted one bit.
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The letters and numbers in HEX are:
Char ASCII Call Char ASCII Call
(BLANK) 20 40 S 53 A6
A 41 82 T 54 A8
B 42 84 U 55 AA
C 43 86 V 56 AC
D 44 88 W 57 AE
E 45 8A X 58 B0
F 46 8C Y 59 B2
G 47 8E Z 5A B4
H 48 90 0 30 60
I 49 92 1 31 62
J 4A 94 2 32 64
K 4B 96 3 33 66
L 4C 98 4 34 68
M 4D 9A 5 35 6A
N 4E 9C 6 36 6C
O 4F 9E 7 37 6E
P 50 A0 8 38 70
Q 51 A2 9 39 72
R 52 A4
A seventh callsign value is the secondary station ID (SSID).
This is a value from 0 through 15 and is encoded as:
Bit 7 6 5 4 3 2 1 0
0 1 1 D C B A 0
where D is the most significant bit and A the least in the binary
value (0 through 15).
Note 5
Parity for the asynchronous serial port is:
Value Meaning
0 None
1 Odd
2 None
3 Even
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Tucson Amateur Packet Radio TNC 2 System Manual
Note 6
Binary status and parameter elements (commands whose arguments
are ON/OFF) are encoded as
ON = TRUE = 1
OFF = FALSE = 0
Commands which are "negative-true logic" (FALSE = 1 and TRUE = 0)
are indicated by trailing asterisks (*).
There are several defaults that are encoded on a bit basis.
These are listed below.
American Radio Relay League, The 1985 ARRL Handbook for the Radio
Amateur, 1984, pp. 19-21 through 19-31.
American Radio Relay League, Proceedings of the First ARRL
Amateur Radio Computer Networking Conference, October 16-17,
1981.
American Radio Relay League, Proceedings of the Second ARRL
Amateur Radio Computer Networking Conference, March 19, 1983.
American Radio Relay League, Proceedings of the Third ARRL
Amateur Radio Computer Networking Conference, April 15, 1984.
American Radio Relay League, Proceedings of the Fourth ARRL
Amateur Radio Computer Networking Conference, March 30, 1985.
American Radio Relay League, Proceedings of the Fifth ARRL
Amateur Radio Computer Networking Conference, March 9, 1986.
American Radio Relay League, Proceedings of the Sixth ARRL
Amateur Radio Computer Networking Conference, August 29, 1987.
American Radio Relay League, Proceedings of the Seventh ARRL
Amateur Radio Computer Networking Conference, October 1, 1988.
American Radio Relay League, Proceedings of the Eighth ARRL
Amateur Radio Computer Networking Conference, October 7, 1989.
American Radio Relay League, Proceedings of the Ninth ARRL/CRRL
Amateur Radio Computer Networking Conference, September 22, 1990.
American Telephone and Telegraph Company, "Operations Systems
Network Communications Protocol Specification BX.25," Issue 2,
Publication 54001, 1979.
David W. Borden, K8MMO, and Paul L. Rinaldo, W4RI, "The Making of
an Amateur Packet-Radio Network," QST, October 1981, pp. 28-30.
D. W. Davies, D. L. A. Barber, W. L. Price and C. M. Solomonides,
Computer Networks and Their Protocols, John Wiley and Sons, 1979.
Exar Integrated Systems, "Phase-Locked Loop Data Book," Exar
Applications Note AN-01, P. O. Box 62229, Sunnyvale, CA 94088,
1981.
197
Tucson Amateur Packet Radio TNC 2 System Manual
Terry Fox, WB4JFI, "AX.25 Amateur Packet-Radio Link-Layer
Protocol, Version 2.0," ARRL, October, 1984 (Available from ARRL
for $8).
International Standards Organization, "Reference Model of Open
Systems Architecture," Document ISO/TC97/SC16/N227, June 1979.
Lyle Johnson, WA7GXD, "Join the Packet-Radio Revolution," 73
Magazine, September, 1983, pp. 19-24.
Lyle Johnson, WA7GXD, "Join the Packet-Radio Revolution - Part
II," 73 Magazine, October, 1983, pp. 20-31.
Lyle Johnson, WA7GXD, "Join the Packet-Radio Revolution - Part
III," 73 Magazine, January, 1984, pp. 36-44.
Margaret Morrison, KV7D, and Dan Morrison, KV7B, "Designing the
TAPR TNC Audio Input Filter," Proceedings of the Second ARRL
Amateur Radio Computer Networking Conference, March 19, 1983, p.
54.
Margaret Morrison, KV7D, and Dan Morrison, KV7B, "Amateur Packet
Radio: part 1," Ham Radio, July 1983, pp. 14-25.
Margaret Morrison, KV7D, Dan Morrison, KV7B, and Lyle Johnson,
WA7GXD, "Amateur Packet Radio: part 2," Ham Radio, August 1983,
pp. 18-28.
National Semiconductor, "Technical Product Information, MF10",
2900 Semiconductor Drive, Santa Clara, CA 95051.
Harold E. Price, NK6K, "Multi-use Design Considerations for the
TAPR TNC," Proceedings of the Second ARRL Amateur Radio Computer
Networking Conference, March 19, 1983, p. 62.
Harold Price, NK6K, "What's All This Racket About Packet?" QST,
July, 1985, pp. 14-17.
Harold Price, NK6K, "A Closer Look at Packet Radio," QST, August,
1985, pp. 17-20.
Andrew S. Tanenbaum, Computer Networks, Prentice-Hall, 1981.
