
; B5NH-1.INS - BYE5 insert for North Star Horizon computers - 10/15/85
;
;		8251A and no baudrate generator
;
; Pin 8 (DCD) from the modem must be connected to the USART's DSR input,
; normally Pin 6.
;
;	     Note:  This is an insert, not an overlay.
;
;
; =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =
;
; 10/15/85  Original version for BYE5		- Irv Hoff
;
; =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =   =
;
;
;The following define the port address to use
;
PORT	EQU	4H		; Data port
MDCTL1	EQU	PORT+1		; Status/control port
;
BPORT	EQU	MDCTL1		; Baud rate port=8251 control
;
;
;-----------------------------------------------------------------------
;
;
; See if we still have a carrier - if not, return with the zero flag set
;
MDCARCK:IN	MDCTL1		; Get status
	ANI	80H		; Check DSR bit for a carrier
	RET
;.....
;
;
; Disconnect and wait for an incoming call
;
MDINIT:	MVI	A,10H		; Clear DTR
	OUT	MDCTL1		; Causing hangup
	PUSH	B		; Preserve in case we need it
	MVI	B,20		; 2 second delay
;
OFFTI:	CALL	DELAY		; 0.1 second delay
	DCR	B
	JNZ	OFFTI		; Keep looping until finnished
	POP	B		; Restore BC
	MVI	A,17H		; Assert DTR so that modem
	OUT	MDCTL1		; Can answer phone
	XCHG			; Small delay
	XCHG			; Small delay
;
	 IF	IMODEM
	CALL	IMINIT
	 ENDIF			; IMODEM
;
	RET
;.....
;
;
; Input a character from the modem port
;
MDINP:	IN	PORT		; Get character
	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:	IN	MDCTL1		; Get status
	ANI	02H		; Check the receive ready bit
	RZ			; Return if none
	ORI	0FFH		; We have a character
	RET
;.....
;
;
; Send a character to the modem
;
MDOUTP:	OUT	PORT		; Send it
	RET
;.....
;
;
; See if the output is ready for another character
;
MDOUTST:IN	MDCTL1
	ANI	01H		; Check the transmit ready bit
	RET
;.....
;
;
; Reinitialize the modem and hang up the phone by dropping DTR and
; leaving it inactive.
;
MDQUIT:	 IF	IMODEM
	CALL	IMQUIT		; Tell modem to quit
	 ENDIF			; IMODEM
;
;
; Called by the main program after caller types BYE
;
MDSTOP:	MVI	A,10H		; Turn off DTR
	OUT	MDCTL1
	RET
;.....
;
;
; The following routine sets the baudrate.  BYE5 asks for the maximum
; speed you have available.
;
SET2400	EQU	$		; Only supports 300/1200
;
SETINV:	ORI	0FFH		; Make sure zero flag not set
	RET
;.....
;
;
SET300:	MVI	B,BD300
	JMP	SETBAUD
;
SET1200:MVI	B,BD1200
;
SETBAUD:MVI	A,47H		; Reset, enable Rx, DTR, Tx
	OUT	MDCTL1		; Rx,Tx enabled
	XCHG			; Small delay
	XCHG			; Small delay
	MOV	A,B		; Recover Baud Rate Word
	OUT	BPORT
	XCHG			; Small delay
	XCHG			; Small delay
	MVI	A,17H		; ERR reset, DTR, Rx, Tx all on
	OUT	MDCTL1
	XCHG			; Small delay
	XCHG			; Small delay
	XRA	A		; Say rate OK
	RET
;.....
;
;
; Values to switch the 8251 between x16 and x64 300 or 1200 bps
;
BD300	EQU	4FH		; 300 baud
BD1200	EQU	4EH		; 1200 bps
;
;
;			       end
;------------------------------------------------------
