;
; MODULE: T3T-24-1 (Telephone Interface) for Hayes-compatible 2400bps modems
; Author: David McCord/Richard Conn
; Version: 1.0
; Date: 23 May 86
; Previous Versions: Richard Conn wrote T3TI-SM v1.2, which this is based on.
; Comments: This TI supports 300/1200/2400bps Hayes-compatible modems.  A key
;           compatibility point is that the modem return the terse result code
;           "10" on CONNECT 2400.  Modems that should work with this TI include
;           the Hayes 2400, USR Courier 2400, and Racal-Vadic 2400V.  Developed
;           and tested on a Courier 2400.  Baud rate is automatically set upon
;           connection in answer or originate modes.  The answer routines have
;           been rewritten from the original to NOT use modem auto-answer
;           functions, as this can lead to the modem answering the phone when
;           it shouldn't.
;
	ORG	700H		; BASE ADDRESS (700H - 9FFH)
;
;  ACCESS TO FILER$SERVER WITHIN T3ANSWER, T3DIAL, T3HANGUP, T3INIT
;
FILER$SERVER	EQU	11AH	; ADDRESS OF ADDRESS
FS$GETSPEED	EQU	0	; GET PROCESSOR SPEED
FS$WAIT1S	EQU	1	; WAIT 1 SEC
FS$WAITP1S	EQU	2	; WAIT 0.1 SEC
FS$WAIT1MS	EQU	3	; WAIT 0.001 SEC
FS$CST		EQU	4	; CONSOLE STATUS (Z=RDA)
FS$CIN		EQU	5	; CONSOLE INPUT
FS$COUT		EQU	6	; CONSOLE OUTPUT (CHAR IN C)
;
;  ACCESS TO MODEM OVERLAY ROUTINES
;
M1$INIT		EQU	600H		; INITIALIZE MODEM
M1$ISTAT	EQU	M1$INIT+3	; INPUT STATUS
M1$OSTAT	EQU	M1$ISTAT+3	; OUTPUT STATUS
M1$IN		EQU	M1$OSTAT+3	; INPUT BYTE
M1$OUT		EQU	M1$IN+3		; OUTPUT BYTE
M1$BREAK	EQU	M1$OUT+3	; SEND BREAK
M1$CST		EQU	M1$BREAK+3	; CARRIER STATUS DETECT
M1$SPTAB	EQU	M1$CST+3	; SPEED BYTE
;
;  ASCII CONSTANTS
;
CR	EQU	0DH
CTRLC	EQU	'C'-'@'
;
;  Telephone System Interface Routines
;
TI$INIT:
	JP	STI$INIT	; INITIALIZATION
TI$ANS:
	JP	STI$ANS		; SET ANSWER MODE
TI$HANG:
	JP	STI$HANG	; HANG UP PHONE
TI$RST:
	JP	STI$RST		; RING STATUS DETECT
TI$DSTRT:
	JP	STI$DSTRT	; START DIALING
TI$DSTOP:
	JP	STI$DSTOP	; STOP DIALING
TI$DIGIT:
	JP	STI$DIGIT	; DIAL DIGIT
TI$PREPANS:
	JP	STI$PREPANS	; PREPARE FOR ANSWERING PHONE
TI$GETBAUD:
	JP	STI$GETBAUD	; RETURN CURRENT BAUD RATE VALUE
;
;  FILER$SERVER INTERFACE FOR TELEPHONE INTERFACE OVERLAY
;  FILER$SERVER CODE IS IN A
;
TI$FS:
	PUSH	HL		; SAVE HL
	LD	HL,TI$FSRET	; SET RETURN ADDRESS
	PUSH	HL		; ... ON STACK
	LD	HL,(FILER$SERVER)	; GET ADDRESS OF FILER$SERVER
	JP	(HL)		; "CALL" ROUTINE
TI$FSRET:
	POP	HL		; RESTORE HL
	RET
;
;  SEND 'ATx' COMMAND TO SMARTMODEM
;
CMD$SEND:
	PUSH	AF		; SAVE CMD
	LD	A,FS$WAIT1S	; CODE TO WAIT 1 SECOND
	CALL	TI$FS		; FILER$SERVER
	LD	A,'A'		; SEND 'AT'
	CALL	CMD$SEND1
	LD	A,'T'
	CALL	CMD$SEND1
	POP	AF		; GET CMD
;
;  SEND FURTHER COMMAND CHARS TO SMARTMODEM
;
CMD$SEND1:
	PUSH	AF		; SAVE CHAR
	CALL	M1$OUT		; SEND CHAR IN A
	push	bc
	ld	b,10		; do this 10 times...
cmd$send2:
	ld	a,fs$wait1ms
	call	ti$fs		; wait a millisecond
	djnz	cmd$send2
	pop	bc		; when we get here, we waited 10ms for echo
	CALL	FLUSH		; flush the echo
	POP	AF
	RET
;
;  END SMARTMODEM COMMAND SEQUENCE
;
CMD$END:
	PUSH	AF		; SAVE A
	LD	A,0DH		; SEND <CR> AND WAIT FOR <CR>
	CALL	CMD$SEND1	; SEND CHAR WITH ECHO
	POP	AF		; RESTORE A
	RET
;
;  WAIT FOR RESPONSE FROM SMARTMODEM COMMAND
;    RETURN DIGIT UNLESS ERROR:
;	A=0FFH if TIMEOUT
;	A=0FEH if USER ABORT
;
ssresponse:
	push	hl
	ld	hl,500		; super short delay for response (.5 sec)
	jr	respe
SRESPONSE:
	PUSH	HL
	LD	HL,2000		; SHORT DELAY FOR RESPONSE (2 secs)
	JR	RESPE
RESPONSE:
	PUSH	HL		; SAVE HL
	LD	HL,30000	; LARGE DELAY FOR RESPONSE (30 secs)
RESPE:
	LD	(RESP$DELAY),HL
RESP1:
	LD	HL,(RESP$DELAY)	; DELAY FOR RESPONSE
RESP2:
	CALL	M1$ISTAT	; INPUT CHAR FROM MODEM?
	JR	NZ,RESPM
	LD	A,FS$CST	; CONSOLE STATUS
	CALL	TI$FS		; USER ABORT?
	JR	Z,RESP3
	ld	a,fs$wait1ms
	call	ti$fs		; wait 0.001 sec
	DEC	HL		; COUNT DOWN
	LD	A,H		; DONE?
	OR	L
	JR	NZ,RESP2
	POP	HL
	OR	0FFH		; TIMEOUT CODE
	RET
RESP$DELAY:
	DS	2		; RESPONSE DELAY
;
; PROCESS USER CHAR
;
RESP3:
	LD	A,FS$CIN	; GET USER INPUT
	CALL	TI$FS		; USE FILER$SERVER
	AND	7FH		; MASK
	CP	CTRLC		; ABORT?
	JR	NZ,RESP2
	POP	HL		; RESTORE HL
	LD	A,0FEH		; USER ABORT
	OR	A
	RET
;
; PROCESS MODEM CHAR
;
RESPM:
	CALL	M1$IN		; GET CHAR
	AND	7FH		; MASK
	JR	Z,RESP1		; FLUSH NULL
	POP	HL		; RESTORE HL
	RET
;
;  ATTRACT ATTENTION OF SMARTMODEM
;
ATTENTION:
	CALL	M1$CST		; DO NOTHING IF NO CARRIER
	RET	Z
	CALL	FLUSH		; FLUSH ANY CHAR
	LD	A,0		; SEND AT LEAST ONE CHAR FIRST
	CALL	M1$OUT
	LD	A,FS$WAIT1S	; WAIT 1 SEC
	CALL	TI$FS		; USE FILER$SERVER
	LD	A,'+'		; ATTRACT MODEM'S ATTENTION
	CALL	M1$OUT
	CALL	M1$OUT
	CALL	M1$OUT
	CALL	sresponse	; WAIT FOR RESPONSE OR TIMEOUT
	RET
;
;  FLUSH ANY GARBAGE CHARS FROM COMMAND LINE
;
FLUSH:
	CALL	M1$ISTAT	; ANY CHARS?
	RET	Z		; RETURN IF NONE
	CALL	M1$IN		; GET CHAR
	RET
;
;  Telephone Interface Initialization
;	Function:  Initialize the Modem/UART Interface
;	Input Parameters:  None
;	Output Parameters:  None
;
STI$INIT:
	PUSH	AF		; SAVE A
	CALL	ATTENTION	; GET MODEM'S ATTENTION
	LD	A,'Z'		; RESET MODEM
	CALL	CMD$SEND	; SEND COMMAND
	CALL	CMD$END		; SEND <CR>
	CALL	OK		; GET OK/USER ABORT
	CP	0FEH		; USER ABORT?
	JR	Z,STI$INI1
	LD	A,'V'		; SET NON-VERBOSE MODE
	CALL	CMD$SEND	; SEND COMMAND
	LD	A,'0'		; V0 COMMAND
	CALL	CMD$SEND1
	LD	A,'X'		; SET EXTENDED COMMAND SET
	CALL	CMD$SEND1	; SEND COMMAND
	LD	A,'4'		; Enable result codes 0 thru 10
	CALL	CMD$SEND1
	ld	a,'S'		; disable auto-answer if turned on somehow
	call	cmd$send1
	ld	a,'0'
	call	cmd$send1
	ld	a,'='
	call	cmd$send1
	ld	a,'0'
	call	cmd$send1
	CALL	CMD$END		; SEND <CR>
	CALL	OK1		; GET OK/USER ABORT
STI$INI1:
	CALL	FLUSH		; FLUSH RESPONSES
	POP	AF		; RESTORE A
	RET
;
; GET RESPONSE CODE OF 'OK' OR '0'
;
OK:
	CALL	sresponse	; GET FIRST CHAR
	CP	0FEH		; USER ABORT?
	RET	Z
	CP	'0'		; DIGIT '0'?
	JR	Z,OK1A
	CP	'O'		; LETTER 'O'?
	JR	NZ,OK
	CALL	sresponse	; GET 'K'
	CP	0FEH		; USER ABORT?
	RET	Z
	CALL	sresponse	; GET <CR>
	CP	0FEH		; USER ABORT?
	RET	Z
	CALL	sresponse	; GET <LF>
	RET
;
; GET RESPONSE CODE OF '0'
;
OK1:
	CALL	sresponse	; GET FIRST CHAR
	CP	0FEH		; USER ABORT?
	RET	Z
	CP	'0'		; OK?
	JR	NZ,OK1
OK1A:
	CALL	sresponse	; GET <CR>
	RET
;
;  Prepare Modem to Answer Phone
;	Function:  To condition modem for answering phone
;	Input Parameters:  None
;	Output Parameters:  None
;
STI$PREPANS:
	PUSH	AF
	LD	A,3		; SELECT 2400 BAUD
	LD	(STI$BRATE),A	; SET FLAG
	CALL	M1$INIT
	POP	AF
	RET
;
;  Set Modem to Answer
;	Function:  Set Modem to Answer Mode
;	Input Parameters:  None
;	Output Parameters:  A=0 IF NOT SUCCESSFUL, A=0FFH IF SUCCESSFUL
;
STI$ANS:
	XOR	A		; SET NO BAUD RATE
	LD	(STI$BRATE),A
	ld	a,'A'		; prepare to send ATA command
	call	cmd$send	; send it
	call	cmd$end
STI$ANS1:
	call	response
	CP	CR		; <CR>?
	JR	Z,STI$ANS1
	cp	'1'		; is it "1" or "10" (300 or 2400)?
	jr	z,sti$ans324	; If Z, process further
	CP	'5'		; CONNECT 1200?
	JR	Z,STI$ans12
	xor	a		; make A 0 (we didn't get a connect)
	ret
sti$ans324:
	call	ssresponse	; we should have at least a CR or a 0 pending
	cp	cr		; is it CR?
	jr	z,sti$ans3	; must be 300 if Z
sti$ans24:
	ld	a,3		; select 2400 bps
	jr	sti$ansset
STI$ans3:
	LD	A,1		; SELECT 300 BAUD
	JR	STI$ansSET
STI$ans12:
	LD	A,2		; SELECT 1200 BAUD
STI$ansSET:
	LD	(STI$BRATE),A	; SET BAUD RATE
	CALL	M1$INIT		; INIT USART BAUD RATE
	OR	A,0ffh		; RETURN CONNECT CODE
	RET
;
;  Hang up telephone
;	Function:  Place the telephone on hook
;	Input Parameters:  None
;	Output Parameters:  None
;
STI$HANG:
	PUSH	AF
	CALL	M1$CST		; DO NOT HANG UP IF NO CARRIER
	JR	Z,STI$HANG1
	CALL	STI$HANG3	; HANG UP PHONE
	CP	0FEH		; USER ABORT?
	JR	Z,STI$HANG1
	CALL	M1$CST		; STILL CARRIER?
	JR	Z,STI$HANG1
	CALL	STI$HANG3	; TRY A SECOND TIME TO HANG UP
STI$HANG1:
	POP	AF		; DO NOTHING SINCE WE ARE ALREADY OFFLINE
	RET
STI$HANG3:
	CALL	ATTENTION	; GET SMARTMODEM'S ATTENTION
	LD	A,'H'		; HANG UP PHONE
	CALL	CMD$SEND
	CALL	CMD$END		; END OF COMMAND
	CALL	sresponse	; FLUSH RESPONSE DIGIT
	CP	0FEH		; USER ABORT
	RET	Z
	CALL	sresponse	; FLUSH RESPONSE <CR>
	RET
;
;  YES and NO Return Codes
;
STI$YES:
	OR	0FFH		; SET FLAGS
	RET
STI$NO:
	XOR	A		; NO ANSWER
	RET
;
;  Ring Status Detect
;	Function:  Determines if phone is ringing or not.
;	Input Parameters:  None
;	Output Parameters:  A=0FFH no ring, A=0 ring, A=0FEH user abort
;
STI$RST:
	CALL	ssresponse	; GET RETURN CODE
	cp	0dh		; cr?
	jr	z,sti$rst
	CP	'2'		; RING?
	JR	Z,STI$RST3
	CP	0FEH		; USER ABORT?
	JR	Z,STI$RST2
STI$RST1:
	LD	A,0FFH		; RETURN NO RING
STI$RST2:
	OR	A		; SET FLAGS
	RET
sti$rst3:
	call	ssresponse	; get trailing CR
	cp	0feh		; user abort?
	jr	z,sti$rst2
	xor	a
	ret
;
;  Start Dialing
;	Function:  Initiate the dialing process
;	Input Parameters:  None
;	Output Parameters:  A=0 if no dial tone, A=0FFH if dial tone
;
STI$DSTRT:
	CALL	FLUSH		; FLUSH CHAR IF PRESENT
	LD	A,3		; SELECT 2400 BAUD
	LD	(STI$BRATE),A	; SET BAUD RATE
	CALL	M1$INIT
	LD	A,'D'		; START DIALING
	CALL	CMD$SEND	; SEND COMMAND
	LD	A,'T'		; TOUCH TONE DIALING
	CALL	CMD$SEND1
	JP	STI$YES		; fake dial tone OK, even though we aren't
				; off-hook yet
;
;  Stop Dialing
;	Function:  Terminate the dialing process with answer or user abort,
;                  and set baud rate based on result code if answer.
;	Input Parameters:  None
;	Output Parameters:  A=0 and Z if answer, NZ and error code if no ans
;				Error Code: 0FFH=Timeout, 0FEH=User Abort
;					Other=TI Return Code
;
STI$DSTOP:
	ld	a,cr		; end dial string
	call	cmd$send1
STI$DS1:
	LD	A,FS$CST	; CHECK CONSOLE STATUS
	CALL	TI$FS		; USE FILER$SERVER
	JR	Z,STI$DS2	; NO CONNECTION IF USER ABORT
STI$DSLOOP:
	CALL	RESPONSE	; ANSWER?
	CP	0FFH		; TIMEOUT?
	JR	Z,STI$DS1
	CP	0FEH		; USER ABORT
	JR	Z,STI$DS2E
	CP	'2'		; RING?
	JR	Z,STI$DSLOOP
	CP	CR		; <CR>
	JR	Z,STI$DSLOOP
	CP	'9'+1		; CHECK RANGE
	JR	NC,STI$DS1
	CP	'0'		; CHECK RANGE
	JR	C,STI$DS1
	CP	'1'		; is it a "1" or "10"?
	JR	Z,STI$DS324	; process more if so
	CP	'5'		; CONNECTED AT 1200 BAUD?
	ret	nz
	LD	A,2		; SELECT 1200 BAUD
STI$DSB:
	LD	(STI$BRATE),A	; SET BAUD RATE FLAG
	CALL	M1$INIT		; SET BAUD RATE
	XOR	A		; RETURN CONNECT CODE
	RET
STI$DS2:
	LD	A,FS$CIN	; GET CHAR
	CALL	TI$FS		; USE FILER$SERVER
	AND	7FH
	CP	CTRLC		; ABORT?
	JR	NZ,STI$DS1
STI$DS2E:
	LD	A,0FEH		; SET USER ABORT
	OR	A
	RET
sti$ds324:
	call	ssresponse	; there is at least a CR or 0 pending
	cp	cr		; was it cr, not 0?
	jr	z,sti$ds3	; if yes, go set 300 baud
sti$ds24:
	ld	a,3		; select 2400 bps
	jr	sti$dsb
STI$DS3:
	LD	A,1		; SELECT 300 BAUD
	JR	STI$DSB
;
;  Dial Digit
;	Function:  Dial an individual digit
;	Input Parameters:  A=ASCII for digit to dial
;	Output Parameters:  None
;
STI$DIGIT:
	PUSH	AF
	CP	' '		; DON'T SEND SPACES
	jr	z,sti$digit1
	cp	'-'		; don't send dashes
	jr	z,sti$digit1
	cp	'('		; don't send parenthesis
	jr	z,sti$digit1
	cp	')'		; other kind
	jr	z,sti$digit1
	CALL	CMD$SEND1	; SEND DIGIT WITH ECHO
sti$digit1:
	POP	AF
	RET
;
;  Get Baud
;	Function:  Return current baud rate value (from answer or dial)
;	Input Parameters: None
;	Output Parameters: A = Baud Rate and Z flag set
;		A = 0 means undefined
;		A = 1 means  300 baud
;		A = 2 means 1200 baud
;
STI$GETBAUD:
	LD	A,(STI$BRATE)	; GET VALUE
	OR	A		; SET FLAGS
	RET
;
;  BAUD RATE FLAG
;	A = 0 IF NONE
;	A = 1 IF  300 BAUD
;	A = 2 IF 1200 BAUD
;
STI$BRATE:
	DB	0		; FLAG BUFFER
;
;		END of Telephone Interface Routines
;
	DB	'End of TI-2400'

	END