Cleanups to make code nicer looking. ALU subtraction fixes.

[fpgaboy.git] / rom.asm

	SECTION "a",HOME

main:
	ld c, $51	; Note that we are alive.
	ld a, $FF
	ld [c],a
	
	ld sp, $DFF0
	
	ld hl, $DF81
	ld a, $80
	ld [hl], a

;	ld c, $07
;	ld a, $04	;start timer, 4.096KHz
;	ld [c], a
diqs:;	ei
	jr diqs

	ld hl, signon
	call puts

	
	ei
	
	call memtest

	call insntest

	call waitsw
	di

	jr main

	section "fuq",HOME[$50]
irqhand:
	PUSH AF
	PUSH BC
	PUSH DE
	PUSH HL
	
;	ld c, $51
;	ld a, $F0
;	ld [c], a
	
	xor a
	ld c, $0F	; ack the irq
	ld [c], a
	
	;ld a, $41	; print A
	;call putc
	
	ld hl, $DF81
	ld a, [hl]
;	ld b, 1
;	add b
	ld c, $51
;	ld [c], a
;	ld [hl], a


;	ld c, $51
;	ld a, $0F
;	ld [c], a
	
	POP HL
	POP DE
	POP BC
	POP AF
	RETI

signon:
	db $0D,$0A,$1B,"[1mFPGABoy Diagnostic ROM",$1B,"[0m",$0D,$0A,0

; Memory tester: writes h ^ l to all addresses from C000 to DF80.
memtest:
	ld hl,memteststr
	call puts
	
	ld hl, $C001		; Write loop
.wr:
	ld a,h
	xor l
	ld [hli],a
	ld a, $DF
	cp h
	jr nz, .wr
	ld a, $80
	cp l
	jr nz, .wr

	ld hl, $C001		; Read loop
.rd:
	ld a,h
	xor l
	ld b,a
	ld a, [hli]
	cp b
	jr nz, .memfail
	
	ld a, $DF
	cp h
	jr nz, .rd
	ld a, $80
	cp l
	jr nz, .rd
	
	ld hl, testokstr	; Say we're OK
	call puts
	ret
.memfail:			; Say we failed (sadface)
	; decrement hl the easy way
	ld a,[hld]
	push hl
	ld hl, failatstr
	call puts
	pop hl
	ld a, h
	call puthex
	ld a, l
	call puthex
	ld a, $0A
	call putc
	ld a, $0D
	call putc
	ret
memteststr:
	db "Testing memory from $C000 to $DF80...",0
testokstr:
	db " OK!",$0D,$0A,0
failatstr:
	db " Test failed at $",0

puthex:				; Put two hex nibbles to the serial console.
	push af
	rra
	rra
	rra
	rra
	ld b,$0F
	and b
	ld b,$30
	add b
	call putc
	pop af
	ld b,$0F
	and b
	ld b,$30
	add b
	call putc
	ret

; Wait for switches to be flipped on and off again.
waitsw:
	ld hl,waitswstr
	call puts

	ld c, $51
	xor a
	ld [c],a
	
	ld b, $0
.loop1:
	ld a,[c]
	cp b
	ei
	jr z,.loop1
.loop2:
	ld a,[c]
	cp b
	jr nz,.loop2
	ret

waitswstr:
	db "Diagnostic ROM complete; flip switches to nonzero and then to zero to reset. Expect A.",$0D,$0A,0

; Core instruction basic acceptance tests.
insntest:
	ld hl, .insnteststr
	call puts
	
	; Test PUSH and POP.
	ld b, $12
	ld c, $34
	ld d, $56
	ld e, $78
	push bc
	pop de
	ld hl, .pushpopfail
	ld a, d
	cp b
	jr nz,.fail
	ld a, e
	cp c
	jr nz,.fail
	
	; Test ALU (HL).
	ld hl, .ff
	ld a, $FF
	xor [hl]
	ld hl, .xorhlfail
	jr nz, .fail
	
	; Test JP (HL)
	ld hl, .jphl
	jp [hl]
	ld hl, .jphlfail
	jr .fail
	rst $00
.jphl:

	; Test JR
	ld a, $FF
	ld b, $00
	cp b
	jr nz,.jr
	ld hl, .jrfail
	jr .fail
	rst $00
.jr:

	; Test inc16
	ld d, $12
	ld e, $FF
	ld hl, .inc16fail
	inc de
	ld a, $13
	cp d
	jr nz, .fail
	ld a, $00
	cp e
	jr nz, .fail
	
	; Test CP.
	ld hl, .cpfail
	ld a, $10
	ld b, $20
	cp b
	jr nc,.fail
	ld a, $20
	ld b, $10
	cp b
	jr c,.fail
	
	; Test CPL
	ld hl, .cplfail
	ld a, $55
	ld b, $AA
	cpl
	cp b
	jr nz,.fail
	
	ld hl, .ok
	call puts
	ret
.fail:
	call puts
	ld hl, .testfailed
	call puts
	ret
.insnteststr:
	db "Testing instructions... ",0
.pushpopfail:
	db "PUSH/POP",0
.ff:
	db $FF
.xorhlfail:
	db "XOR [HL]",0
.jphlfail:
	db "JP [HL]",0
.jrfail:
	db "JR",0
.cpfail:
	db "CP",0
.cplfail:
	db "CPL",0
.inc16fail:
	db "INC16",0
.testfailed:
	db " test failed.",$0D,$0A,0
.ok:
	db "OK!",$0D,$0A,0

; Serial port manipulation functions.
putc:
	ld b, 0
	ld c, $50
	push af
.waitport:
	ld a,[c]
	cp b
	jr nz,.waitport
	pop af
	ld [c],a
	ret

puts:
	ld a, [hli]
	ld b, $00
	cp b
	ret z
	call putc
	jr puts