;*****************************************************************
;*								*
;*        disassembly of XTALK version 3.0 bios 			*
;*								*
;*****************************************************************
base	equ	48h		; base i/o address 
rbr	equ	base		; ACE receiver buffer register
thr	equ	base		; ACE transmitter holding register
dll	equ	base		; ACE baud rate divisor latch (lsb)
dlm	equ	base+1		; ACE baud rate divisor latch (msb)
ier	equ	base+1		; ACE interrupt enable register
clk	equ	base+2		; WB14 printer select port
lcr	equ	base+3		; line control register
mcr	equ	base+4	;modem control register (JCS ENHANCEMENT)
lsr	equ	base+5		; line status register
msr	equ	base+6		; modem status register
grpsel	equ	base+7		; group select bit

dtron	equ	1	;pin 20  high Data Terminal Ready (JCS ENHANCEMENT)
dlab	equ	80h		; divisor latch access bit
thre	equ	20h		; transmitter holding reg. empty mask
dsr	equ	20h		; data set ready mask
rrf	equ	01h		; receive register full mask
dcd	equ	80h		; data carrier detect mask
SB	EQU	40H		; SET BREAK

wl5	equ	00h		; 5 bit word length
wl6	equ	01h		; 6 bit word length
wl7	equ	02h		; 7 bit word length
wl8	equ	03h		; 8 bit word length

wl	equ	wl8		;******* set to proper word length *******

st1	equ	00h		; 1 stop bit
st2	equ	04h		; 2 stop bits

st	equ	st1		;******* set to proper stop bits *********

parn	equ	00h		; no parity
pare	equ	18h		; even parity
paro	equ	08h		; odd parity

par	equ	parn		;******* set to necessary parity *********

lb300	equ	80h		; 300 baud low divisor
hb300	equ	01h		; 	   high divisor

lb600	equ	0c0h		; 600 baud low divisor
hb600	equ	00h		; 	   high divisor

lb1200	equ	60h		; 1200 baud low divisor
hb1200	equ	00h		;	    high divisor

lb2400	equ	30h		; 2400 baud low divisor
hb2400	equ	00h		; 	    high divisor

lb4800	equ	18h		; 4800 baud low divisor
hb4800	equ	00h		;	    high divisor

baudl	equ	lb1200		;******* set to proper baud divisor *****
baudh	equ	hb1200		;******* set to proper baud divisor *****

group	equ	2		;******* set to proper ACE

imask	equ	0		; disable all interrupts on this ACE

	.Z80

;L0100H:	JP	0400H

L0103H:	db	03h		;^C
L0104H:	db	08h		;^H	back space character
L0105H:	db	01h		;^A
L0106H:	db	00h		;^@
L0107H:	db	01h		;SET BIT 0 TO MAKE *DTR OUTPUT LOW 
L0108H:	db	00h		;^@


	JP	L0136H		;get a character from the modem
	JP	L0142H		;send a character to the modem
	JP	L0152H		;see if modem is ready ?
	JP	L0167H		;send a break character to the modem ?
	JP	L0176H
	JP	L0176H
	JP	L01CCH		;null routine- just a return 
	JP	L0176H
	JP	L01CDH		;store a 1 in 107h, the jump to 176h
	JP	L01DCH		;return with carry cleared
	JP	L0142H		;send a character out serial port
	JP	L01DFH		;0 the A register
	JP	L01D5H		;store a 0 in 107h, then jump to 176h
	JP	L01DFH		;0 the A register
	NOP
	NOP
	RET


setgrp:	LD	A,GROUP	;mvi	a,group		; select the ACE
	out	(grpsel),A		; and send it
	LD	A,WL+ST+PAR ;mvi	a,wl+st+par	; no dlab.
	out	(lcr),A
	ret			; and back to where we came from

;*************************************************************************
;*									*
;*	GET A CHARACTER FROM THE MODEM					*
;*									*
;*************************************************************************

;stat:
L0136H:	CALL	L0152H
	RET	C

	call	setgrp		; go set ACE to access 
	in	A,(lsr)		; read line status register
	AND	RRF ;ani	rrf		; mask for receive register full
	ret	Z

;	org	120h
;sin:	call	stat		; set group and get status
;	jz	sin		; and loop until character is ready

	in	A,(rbr)		; get character from receive buffer
	ret

;L0136H	CALL	L0152H
;	RET	C
;	IN	A,(0FFH)	;get status of the modem port 
;	AND	002H
;	RET	Z
;	IN	A,(0FEH)	;get a character from the modem port
;	RET


;*************************************************************************
;*									*
;*	SEND A CHARACTER TO THE MODEM					*
;*									*
;*************************************************************************

sout:
L0142H:	CALL	L0152H
	RET	C
	push	AF;psw		; save character on stack
	call	setgrp		; go set to proper ACE
sout1:	in	A,(lsr)		; read line status register
	AND THRE ;ani	thre		; mask for trans. holding reg. empty
	JP Z,SOUT1; jz	sout1		; loop until it is ready
	pop	AF;psw		; restore character
	out	(thr),A		; and send to trans. holding register
	ret

;L0142H	CALL	L0152H		;check DSR & ? & return with carry clear or set
;	RET	C
;	PUSH	AF		
;
;L0147H	IN	A,(0FFH)	;get status of the modem port 
;	AND	001H		;see if transmitter buffer empty
;	JP	Z,L0147H	;loop until tx buffer empty
;
;	POP	AF
;	OUT	(0FEH),A	;send a character out the serial port
;	RET


;*************************************************************************
;*									*
;*	SEE IF MODEM IS READY (VIA DSR LINE)				*
;*									*
;*************************************************************************

L0152H:	PUSH	BC
 LD	B,A		;PRESERVE A
	CALL	SETGRP
	LD	A,(L0108H)
	OR	A
	JP	NZ,L015FH
	IN	A,(MSR)		;MODEM STATUS REGISTER
	AND	DSR
L015FH:	SCF
	JP	Z,L0164H
	CCF
L0164H: LD	A,B		;RESTORE A
	POP	BC
	RET

;L0152H	PUSH	BC		;preserve BC
;	LD	B,A		;preserve A
;	LD	A,(L0108H)	;load a character (default is 00h (Null)) 
;	OR	A
;	JP	NZ,L015FH
;	IN	A,(0FFH)	;get status of the modem port 
;	AND	080H		;check DSR line
;L015FH	SCF
;	JP	Z,L0164H
;	CCF
;L0164H	LD	A,B		;restore A
;	POP	BC		;restore BC
;	RET


;*************************************************************************
;*									*
;*	MAKE THE ACE SEND A BREAK CHARACTER				*
;*									*
;*************************************************************************

L0167H:	CALL	SETGRP
	LD	A,wl+st+par+SB	;SET BREAK CHARACTER
	OUT	(LCR),A		;TO ACE LINE CONTROL REGISTER
	PUSH	BC
	LD	BC,00C8H
	CALL	0403H
	POP	BC
	JP	L0176H

;L0167H	LD	A,00FH		;send a break character ?
;	OUT	(0FFH),A	;command to modem's 8251
;	PUSH	BC
;	LD	BC,L00C8H
;	CALL	L0403H
;	POP	BC
;	JP	L0176H


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L0176H:	PUSH	HL
	PUSH	BC
L0178H:	LD	HL,L020EH
	LD	A,(L0103H)
	CALL	L01E1H
	JP	NC,L018CH

	LD	A,001H
	LD	(L0103H),A
	JP	L0178H

L018CH:	LD	C,A
	LD	HL,L01FDH	;data at end of bios program code
	LD	A,(L0104H)
	CALL	L01E1H
	ADD	A,C
	LD	C,A
	LD	HL,L0202H
	LD	A,(L0105H)
	CALL	L01E1H
	ADD	A,C
	LD	C,A
	LD	HL,L0207H
	LD	A,(L0106H)
	CALL	L01E1H
	ADD	A,C
	LD	C,A
;	LD	A,003H		;ASSUME THIS IS A MODE INSTRUCTION
;	CALL	L01FAH		;send to the 8251-SET 8251 TO ASYNCHRONOUS
;	CALL	L01FAH		;send to the 8251-   MODE & 64 TIMES BAUD RATE
;	LD	A,040H		;RESET THE 8251 
;	CALL	L01FAH		;send to the 8251
;	LD	A,C		;MODE INSTRUCTION
;	CALL	L01FAH		;send to the 8251
;	LD	A,(L0107H)
;	RLA
;	OR	015H		;COMMAND INSTRUCTION
;	CALL	L01FAH		;send to the 8251
	call	setgrp		; point at correct ACE
	LD A,DTRON;	mvi	a,dtron	;PIN 20 = DATA TERMINAL READY (JCS ENHANCEMENT)
	out	(mcr),A	;bring pin 20 high to turn on modem (JCS ENHANCEMENT)
;	mvi
	LD	a,wl+st+par+dlab	; set dlab + options
	out	(lcr),A		; and send to line control reg.
;	mvi
	LD	a,baudl		; get low byte of baud rate divisor
	out	(dll),A		; and send it
;	mvi
	LD	a,baudh		; now get high byte
	out	(dlm),A		; and send it too
;	mvi
	LD	a,wl+st+par	; set word length, stop bits, and parity
	out	(lcr),A		; and reset line control register (no dlab)
	XOR A;xra	a		; clear accumulator
	out	(lsr),A		; clear data available flag
;	mvi
	LD	a,imask		; get int. mask
	out	(ier),A
	POP	BC
	POP	HL
	OR	A
	RET


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L01CCH:	RET


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L01CDH:	LD	A,001H
	LD	(L0107H),A
	JP	L0176H


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L01D5H:	XOR	A
	LD	(L0107H),A
	JP	L0176H


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L01DCH:	SCF
	CCF
	RET			;return with carry cleared


;*************************************************************************
;*									*
;*									*
;*									*
;*************************************************************************

L01DFH:	XOR	A
	RET


L01E1H:	PUSH	BC
	LD	B,A
L01E3H:	LD	A,(HL)
	INC	HL
	CP	B
	JP	Z,L01F2H	;return with carry clear

	CP	0FFH
	JP	Z,L01F7H	;return with carry set

	INC	HL
	JP	L01E3H

L01F2H:	LD	A,(HL)
	SCF
	CCF
	POP	BC
	RET			;return with carry clear

L01F7H:	SCF
	POP	BC
	RET			;return with carry set


L01FAH:	PUSH	AF
	CALL	SETGRP

;L01FAH	OUT	(0FFH),A	;COMMAND TO modem'S 8251
;	RET


L01FDH:	db	07h
	db	08h
	db	08h
	db	0Ch
	db	0FFh
L0202H:	db	01h
	db	40h
	db	02h
	db	0C0h
	db	0FFh
L0207H:	db	01h
	db	30h
	db	02h
	db	10h
	db	00h
	db	00h
L020CH:	db	0FFh
	db	01h
L020EH:	db	02h

;L00C8H:	EQU	000C8H
	END