X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/298e8085b4f8f70121204fa4aed3a188034f6879..2bcaaabf0bbbb0232fe8ffe0a8943a14159852ab:/xm.asm

diff --git a/xm.asm b/xm.asm
new file mode 100644
index 0000000..d4b5374
--- /dev/null
+++ b/xm.asm
@@ -0,0 +1,88 @@
+	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
\ No newline at end of file