TITLE   'MEX PENRIL 300/1200 AD MODEM OVERLAY V1.0'
;
; (DELETE ABOVE TITLE LINE IF ASSEMBLING WITH ASM)
;
; used smartmodem overlay for MEX: revision 1.2
; Written 04/16/84 by Ronald G. Fowler (V1.2) as an outline.
; This overlay is a modified MXO-VPxx for the Penril.
;
;                       Written by:
;               Bruce Childers & Jon Albers
;               Data - 202-633-0804, 0805, 0806
;                      703-281-7907
;
; This overlay will allow a user to use the Penril 300/1200 AD
; modem and its compatibles (Rixon) with Mex.  This overlay does
; support auto-dial.  You should set the DISC equatte to FALSE
; if you wish to disconnect with DTR.
;
;
; This overlay will work with any modem overlay that terminates
; prior to 0B00H
;
FALSE   EQU     0
TRUE    EQU     NOT FALSE
;
;
DISC    EQU     FALSE           ;<<== CHANGE TO FALSE IF YOU DISC. WITH DTR
;
; SYSTEM CONSTANTS
;
DIALV   EQU     0162H           ;LOCATION OF DIAL VECTOR IN OVERLAY
DISCV   EQU     0165H           ;LOCATION OF DISCONNECT VECTOR IN OVERLAY
DIALOC  EQU     0B00H           ;DIALING CODE GOES HERE
MEX     EQU     0D00H           ;"CALL MEX"
;
; FOLLOWING ARE FUNCTION CODES FOR THE MEX SERVICE CALL PROCESSOR
;
INMDM   EQU     255             ;RETURN CHAR FROM MDM IN A, CY=NO CHR IN 100MS
TIMER   EQU     254
TMDINP  EQU     253             ;B=# SECS TO WAIT FOR CHAR, CY=NO CHAR
CHEKCC  EQU     252             ;CHECK FOR ^C FROM KBD, Z=PRESENT
SNDRDY  EQU     251             ;TEST FOR MODEM-SEND READY
RCVRDY  EQU     250             ;TEST FOR MODEM-RECEIVE READY
SNDCHR  EQU     249             ;SEND A CHARACTER TO THE MODEM (AFTER SNDRDY)
RCVCHR  EQU     248             ;RECV A CHAR FROM MODEM (AFTER RCVRDY)
;
CR      EQU     13
LF      EQU     10
;
;
;
       ORG     DIALV           ;OVERLAY THE DIALING VECTOR
       JMP     DIAL
;
       IF      DISC            ;IF PROVIDING DISCONNECT CODE
       ORG     DISCV           ;OVERLAY THE VECTOR
       JMP     DISCON
       ENDIF
;
; This is the DIAL routine called by MEX to dial a digit. The digit
; to be dialed is passed in the A register.  Note that two special
; codes must be intercepted as non-digits: 254 (start dial sequence)
; and 255 (end-dial sequence).  Mex will always call DIAL with 254
; in the accumulator prior to dialing a number.  Mex will also call
; dial with 255 in A as an indication that dialing is complete. Thus,
; the overlay may use these values to "block" the number, holding it
; in a buffer until it is completely assembled.
; After the 254-start-dial sequence, MEX will call the overlay with
; digits, one-at-a-time.  MEX will make no assumptions about the dig-
; its, and will send each to the DIAL routine un-inspected (some modems,
; like the Smartmodem, allow special non-numeric characters in the
; phone number, and MEX may make no assumptions about these).
;
; After receiving the end-dial sequence (255) the overlay must take
; whatever end-of-dial actions are necessary *including* waiting for
; carrier at the distant end.  The overlay should monitor the keyboard
; during this wait (using the MEX keystat service call), and return
; an exit code to MEX in the A register, as follows:
;
;       0 - Carrier detected, connection established
;       1 - Far end busy (only for modems that can detect this condition)
;       2 - No answer (or timed out waiting for modem response)
;       3 - Keyboard abort (^C only: all others should be ignored)
;       4 - Error reported by modem
;
; <No other codes should be returned after an end-dial sequence>
;
; The overlay should not loop forever in the carrier-wait routine, but
; instead use either the overlay timer vector, or the INMDMV (timed 100
; ms character wait) service call routine.
;
; The DIAL routine is free to use any of the registers, but must return
; the above code after an end-dial sequence
;
       ORG     DIALOC
;
DIAL:   CPI     254             ;START DIAL?
       JZ      STDIAL          ;JUMP IF SO
       CPI     255             ;END DIAL?
       JZ      ENDIAL          ;JUMP IF SO
;
; Not start or end sequence, must be a digit to be sent to the modem
;
       CALL    SEND            ;SEND CHARACTER TO MODEM
       CALL    DELAY1
       RET                     ;ALL DONE
;
; Here on a start-dial sequence
;
STDIAL: CALL    SETUP           ;WAKE UP THE VENTEL
       RET
;
; Here on an end-dial sequence
;
ENDIAL: MVI     A,CR            ;PUT A CR AT THE END
       CALL    SEND            ;SEND CR TO MODEM

WAITPR: MVI     C,INMDM
       CALL    MEX             ;CATCH ANY OUTPUT FROM THE MODEM
       JNC     WAITPR          ;LOOP UNTIL NO MORE CHARACTERS
;
; THE FOLLOWING LOOP WAITS FOR A RESULT FROM THE MODEM (UP TO
; 60 SECONDS: YOU MAY CHANGE THIS VALUE IN THE FOLLOWING LINE).
;
RESULT: MVI     C,60            ;<<== MAXIMUM TIME TO WAIT FOR RESULT
PRWLP:  PUSH    B
       MVI     B,1             ;CHECK FOR A CHAR, UP TO 1 SEC WAIT
       MVI     C,TMDINP        ;DO TIMED INPUT
       CALL    MEX
       POP     B
       JNC     PRTEST          ;JUMP IF MODEM HAD A CHAR
       PUSH    B               ;NO, TEST FOR CONTROL-C FROM CONSOLE
       MVI     C,CHEKCC
       CALL    MEX
       POP     B
       JNZ     PRNEXT          ;IF NOT, JUMP
       MVI     B,CR            ;YES, SHUT DOWN THE MODEM
       MVI     C,SNDCHR
       CALL    MEX
       MVI     A,3             ;RETURN ABORT CODE
       RET
PRNEXT: DCR     C               ;NO
       JNZ     PRWLP           ;CONTINUE
;
; ONE MINUTE WITH NO MODEM RESPONSE (OR NO CONNECTION)
;
PRTIMO: MVI     A,2             ;RETURN TIMEOUT CODE
       RET
;
; MODEM GAVE US A RESULT, CHECK IT
;
PRTEST: ANI     7FH             ;IGNORE ANY PARITY
       CALL    PRANAL          ;TEST THE RESULT
       MOV     A,B             ;A=RESULT (CY SIGNIFICANT HERE TOO)
       PUSH    PSW             ;SAVE IT
PRTLP:  MVI     C,INMDM         ;FLUSH ANY REMAINING COMMAND LINE
       CALL    MEX
       JC      PRCHEK          ;JUMP IF NO INPUT
       CPI     LF              ;GOT SOME ... WAITING FOR EOL
       JNZ     PRTLP           ;EAT ANY IN-BETWEEN
PRCHEK: POP     PSW             ;A HAS MEX RETURN-CODE, CY=1 IF UNKNOWN
       JC      RESULT          ;IF RESULT UNKNOWN, IGNORE IT
       RET
;
PRANAL: MVI     B,0             ;PREP CONNECT CODE
       CPI     'O'             ;"CONNECT"?
       RZ
       INR     B               ;PREP BUSY CODE B=1
       CPI     'B'
       RZ
       INR     B               ;PREP NO CONNECT MSG B=2
       CPI     'N'             ;N=NO CONNECT
       RZ
       MVI     B,4             ;PREP MODEM ERROR
       CPI     'E'             ;E=ERROR
       RZ
       STC                     ;UNKNOWN...
       RET

; FOLLOWING ROUTINE DISCONNECTS THE MODEM USING THE PENRIL
; CTRL-@. ALL REGISTERS ARE AVAILABLE FOR THIS FUNCTION.
; NOTHING RETURNED TO CALLER.

        IF DISC
CTRL@:  EQU     '@'-40H

DISCON: MVI     B,CTRL@
       CALL    SEND
       MVI     B,20            ;Wait 2 secs to let modem recover
       MVI     C,TIMER
       CALL    MEX
       RET
        ENDIF
;
;       SET UP ROUTINE TO WAKE VEN-TEL UP
;
SETUP:  MVI     C,SNDRDY        ;CHECK TO SEE IF MODEM IS ALIVE
       CALL    MEX
       JNZ     SETUP
       MVI     A,CR            ;send first cr of 3
       CALL    SEND
       MVI     B,30            ;Wait to get past banner
       MVI     C,TIMER
       CALL    MEX
KOUT:   MVI     C,SNDRDY
       CALL    MEX
       JNZ     KOUT
       MVI     B,'K'   ;GET READY TO DIAL
       MVI     C,SNDCHR
       CALL    MEX
       CALL    DELAY1
       RET
;
DELAY1: MVI     B,5             ;Delay routine
       MVI     C,TIMER
       CALL    MEX
       RET

;       SEND A CHARACTER TO THE MODEM
;
SEND:   MOV     B,A             ;WHEN CALLING HERE, THE CHAR IS IN A
       MVI     C,SNDCHR
       CALL    MEX
       RET
;                               End of  Overlay
       END


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