[fpgaboy.git] / xm.asm

	SECTION "wee",HOME[$0]
	; this all needs to be PIC!
st:
	ld sp, $CFFF
	xor a
	ld hl, $FF60
	ld [hli], a
	ld [hli], a
	ld [hli], a
nak:
	ld a, $15	; NAK
	call putc+$FF80
	
.ack:	call getc+$FF80
	cp $01	;SOH
	jr z,.soh
	cp $04	;EOT
	jr z, .eot
	cp $18	;CAN
	jr z, .rst
	jr .donak

.eot:
	ld A, $06	; Ack the EOT
	call putc+$FF80
.rst:	rst $00

.soh:	call getc+$FF80	; blk
	call getc+$FF80	; iblk
	xor a
	ld b, a
	ld l, a
	ld h, $C0
.lp:	call getc+$FF80
	ld [hli], a
	add b
	ld b, a
	bit 7, l
	jr z, .lp
.cksm:	call getc+$FF80
	cp b
	jr nz, .donak
	ld hl, $C000
.lp2:	jr z, .doack
	ld a, [hli]
	ld [$FF63], A
	bit 7, l
	jr z,.lp2
.doack:	ld A, $06
	call putc+$FF80
	jr .ack
.donak:	call getc+$FF80		; Wait until the line clears, and then once
	jr .donak		; that happens, getc will cause a NAK.

getc:
	xor d
	xor e
.dgetc:
	dec de
	xor a
	cp d
	jr z, .timeout
	ld a, [$FF53]
	and $02
	jr z, .dgetc
	ld a, [$FF52]
	ret
.timeout:
	ld hl, $D000
	ld a, [hl]
	inc a
	ld [hl], a
	ld [$FF51], a
	jr nak

putc:
	ld c, $53
	push af
.waitport:
	ld a,[c]
	and $01
	jr nz,.waitport
	pop af
	ld [$FF52],a
	ret

	section "a", HOME[$7F]
	nop
Commit	Line	Data
2bcaaabf JW	1	SECTION "wee",HOME[$0]
	2	; this all needs to be PIC!
	3	st:
	4	ld sp, $CFFF
	5	xor a
	6	ld hl, $FF60
	7	ld [hli], a
	8	ld [hli], a
	9	ld [hli], a
	10	nak:
	11	ld a, $15 ; NAK
	12	call putc+$FF80
	13
	14	.ack: call getc+$FF80
	15	cp $01 ;SOH
	16	jr z,.soh
	17	cp $04 ;EOT
	18	jr z, .eot
	19	cp $18 ;CAN
	20	jr z, .rst
	21	jr .donak
	22
	23	.eot:
	24	ld A, $06 ; Ack the EOT
	25	call putc+$FF80
	26	.rst: rst $00
	27
	28	.soh: call getc+$FF80 ; blk
	29	call getc+$FF80 ; iblk
	30	xor a
	31	ld b, a
	32	ld l, a
	33	ld h, $C0
	34	.lp: call getc+$FF80
	35	ld [hli], a
	36	add b
	37	ld b, a
	38	bit 7, l
	39	jr z, .lp
	40	.cksm: call getc+$FF80
	41	cp b
	42	jr nz, .donak
	43	ld hl, $C000
	44	.lp2: jr z, .doack
	45	ld a, [hli]
	46	ld [$FF63], A
	47	bit 7, l
	48	jr z,.lp2
	49	.doack: ld A, $06
	50	call putc+$FF80
	51	jr .ack
	52	.donak: call getc+$FF80 ; Wait until the line clears, and then once
	53	jr .donak ; that happens, getc will cause a NAK.
	54
	55	getc:
	56	xor d
	57	xor e
	58	.dgetc:
	59	dec de
	60	xor a
	61	cp d
	62	jr z, .timeout
	63	ld a, [$FF53]
	64	and $02
65	jr z, .dgetc
66	ld a, [$FF52]
67	ret
68	.timeout:
69	ld hl, $D000
70	ld a, [hl]
71	inc a
72	ld [hl], a
73	ld [$FF51], a
74	jr nak
75
76	putc:
77	ld c, $53
78	push af
79	.waitport:
80	ld a,[c]
81	and $01
82	jr nz,.waitport
83	pop af
84	ld [$FF52],a
85	ret
86
87	section "a", HOME[$7F]
88	nop