; B5MM-1.INS - BYE5 insert for MicroMint SB180 computer - 03/17/86
;
;           Note:  This is an insert, not an overlay.
;
; =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =
;
; 03/17/86  Converted to 8080 source code, as BYE5 is not written in
;           Zilog Z80 mnemonics.  Can now be assembled with ASM.COM or
;           other 8080 assemblers.  Renamed to B5MM for "MicroMint" as
;           there is already a B5SB for the Super Brain computer.
;                                       - Irv Hoff
;
; 10/08/85  Written for use with BYE5.  - Ken Davidson
;
; =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =
;
; NOTE - There is an anomaly with the HD64180 chip that doesn't allow
;        the allow the use of its DCD input in a fashion useful to BYE5.
;        When the DCD input is inactive (false) the chip's receive
;        register is turned off.  Since the chip cannot receive any
;        characters with DCD off, it isn't possible to set up a Hayes
;        compatable modem.  A fix for this is to make a special modem
;        cable which has pins 5 and 8 reversed.  Assuming the modem's
;        CTS signal is always active, the chip's DCD line is always on.
;        The modem's DCD signal then enters the chip through CTS0/.
;        With CTS off, the chip can send and receive characters, and
;        the receive register full status works correctly.  However,
;        the transmit buffer empty status is turned off.  Therefore,
;        when setting up the modem with DCD off, a delay must be
;        inserted after each character is sent to ensure the next
;        character doesn't overrun it.  This fix is something of a
;        a kludge, but works and is the only way around the problem
;        without adding more hardware.  Of course, when a carrier is
;        present, the serial port works correctly.
;
; =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =
;
;
PORT    EQU     00H             ; Modem control port
MDATIN  EQU     PORT+8          ; Data in port
MDATOUT EQU     PORT+6          ; Data out port
MDCTL1  EQU     PORT+4          ; Modem status port
;
MDRCV   EQU     80H             ; Modem receive ready bit
MDSND   EQU     02H             ; Modem send ready bit
MDDCD   EQU     20H             ; Data carrier detect
;
CDSTAT  EQU     02H             ; Carrier detect status
BRPORT  EQU     02H             ; Baud rate generator port
;
IN0     EQU     38EDH           ; Special Hitachi op code pair
OUT0    EQU     39EDH           ; Special Hitachi op code pair
;
;
; Divisors for the HD64180 baudrate generator
;
BD300   EQU     13              ; 300 baud
BD1200  EQU     11              ; 1200 bps
BD2400  EQU     10              ; 2400 bps
BD9600  EQU     8               ; 9600 bps
;
;
;-----------------------------------------------------------------------
;
; See if we still have a carrier - if not, return with the zero flat set
;
MDCARCK:DW      IN0             ; Get the status
       DB      CDSTAT
       CMA
       ANI     MDDCD           ; Check for carrier
       RET
;.....
;
;
; Disconnect and wait for an incoming call
;
MDINIT: MVI     A,10H           ; Reset channel
       DW      OUT0
       DB      PORT
       PUSH    B               ; Save in case it's being used elsewhere
       MVI     B,20            ; 2 second delay to drop any carrier
;
OFFTI:  CALL    DELAY           ; 1 second delay
       DCR     B
       JNZ     OFFTI           ; Keep looping until finished
       POP     B               ; Restore 'BC'
       MVI     A,64H           ; Turn DTR back on
       DW      OUT0
       DB      PORT
;
        IF     IMODEM          ; If using an intellegent modem
       CALL    IMINIT          ; Go initialize it now
        ENDIF                  ; IMODEM
;
       RET
;.....
;
;
; Input a character from the modem port
;
MDINP:  DW      IN0             ; Get the character
       DB      MDATIN
       RET
;.....
;
;
; Check the status to see if a character is available.  If not, return
; with the zero flag set.  If yes, use 0FFH to clear the flag.
;
MDINST: DW      IN0             ; Get the status
       DB      MDCTL1
       ANI     MDRCV           ; Got a character
       RZ                      ; Return if none
       ORI     0FFH            ; Otherwise set the proper flag
       RET
;.....
;
;
; Send a character to the modem
;
MDOUTP: DW      OUT0
       DB      MDATOUT
       RET
;.....
;
;
; See if the output is ready for another character
;
MDOUTST:DW      IN0             ; Get the status
       DB      CDSTAT
       ANI     MDDCD           ; Check for carrier
       JZ      MDST1           ; Jump if present
       CALL    DELAY
       ORI     0FFH
       RET
;
MDST1:  DW      IN0             ; Get the status
       DB      MDCTL1
       ANI     MDSND           ; Ready for a character?
       RET
;.....
;
;
; Reinitialize the modem and hang up the phone by dropping DTR and
; leaving it inactive.
;
MDQUIT:  IF     IMODEM
       CALL    IMQUIT
        ENDIF                  ; IMODEM
;
;
; Called by the main program after caller types BYE
;
MDSTOP: MVI     A,74H           ; Turn off DTR until next time
       DW      OUT0
       DB      PORT
       RET
;.....
;
;
; The following routine sets the baud rate.  BYE5 asks for the maximum
; speed you have available.
;
SETINV: ORI     0FFH            ; Make sure zero flag is not set
       RET
;.....
;
;
SET300: MVI     A,BD300
       JMP     SETBAUD
;
SET1200:MVI     A,BD1200
       JMP     SETBAUD
;
SET2400:MVI     A,BD2400
       JMP     SETBAUD
;
SET9600:MVI     A,BD9600
;.....
;
;
; Sets the baudrate
;
SETBAUD:DW      OUT0
       DB      BRPORT
       XRA     A               ; Say baudrate is ok
       RET
;.....
;
;                              end
;-----------------------------------------------------------------------


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