Make it easy to see what's going wrong.

[fpgaboy.git] / diag.asm

	section "end",HOME[1024]
	nop

	SECTION "a",HOME[$00]

start: jp main
	
	section "vbl",HOME[$40]
	jp vbl
	
	section "lcdc",HOME[$48]
	jp lcdc
	
	section "tmro",HOME[$50]
	jp tmro

main:
	ld a, $FF
	ld c, $51
	ld [c], a

	ld sp, $DFF0
	
	ld a, $04	;start timer, 4.096KHz
	ld c, $07
	ld [c], a
	
	ld hl, $DF81
	xor a
	ld [hli], a
	ld [hli], a
	
	ld hl, signon
	call puts

	call putscreen
	
	ei

	call memtest

	call insntest

	call waitsw
	
	di

	jr main

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

tiles:
	db %11111111
	db %11111111
	db %11000011
	db %11000011
	db %11000011
	db %11000011
	db %11111111
	db %11111111
	
	db %00000000
	db %00000000
	db %00000000
	db %00000000
	db %00000000
	db %00000000
	db %00000000
	db %00000000

putscreen:
	; Wait for vblank
	call .vblwait

	ld hl, $8000	; Copy two tiles.
	ld de, tiles
	ld c, $10
.cloop:	push hl
	ld h, d
	ld l, e
	ld a, [hl]
	inc de
	pop hl
	ld [hli], a
	ld [hli], a
	dec c
	xor a
	cp c
	jr nz, .cloop
	
	ld hl, $9800
.vloop:	call .vblwait
	ld c, $40
	ld b, 0
.loop:	inc b
	ld a, b
	and $01
	ld [hli], a
	ld a, h
	cp $9C
	ret z
	dec c
	xor a
	cp c
	jr nz,.loop
	jr .vloop

.vblwait:
.stat1:	ld a, [$FF41]	; STAT
	and $03
	cp $00
	jp nz, .stat1
.stat2:	ld a, [$FF41]
	and $03
	cp $01
	jr nz, .stat2
	ret

vbl:
	PUSH AF
	PUSH BC
	PUSH DE
	PUSH HL
	
	xor a
	ld [$FF0F], a

	ld a, [$FF51]
	ld b, a
	and $80
	cp $80
	jr nz, .nothing
	ld c, $0

	ld a, b
	and $1
	cp c
	call nz, .scyup
	
	ld a, b
	and $2
	cp c
	call nz, .scydown
	
	ld a, b
	and $4
	cp c
	call nz, .scxup
	
	ld a, b
	and $8
	cp c
	call nz, .scxdown

.nothing:
	POP HL
	POP DE
	POP BC
	POP AF

	RETI

.scyup:	ld hl, $FF42
	inc [hl]
	ret

.scydown:	ld hl, $FF42
	dec [hl]
	ret

.scxup:	ld hl, $FF43
	inc [hl]
	ret

.scxdown:	ld hl, $FF43
	dec [hl]
	ret	
	

lcdc:
	PUSH AF
	PUSH BC
	
	xor a
	ld [$FF0F], a
	
	POP BC
	POP AF
	
	reti
	
tmro:
	PUSH AF
	PUSH BC
	PUSH DE
	PUSH HL
	
	xor a
	ld [$FF0F], a
	
	ld c, $45	; LYC
	ld a, [c]
	inc a
	ld [c], a
	
	ld a, [$DF82]
	cp 0
	jr z, .noprint
	ld a, $41	; print A
	call putc
.noprint:
	ld a, [$DF81]
	inc a
	ld [$DF81], a
	ld [$FF51], a

	POP HL
	POP DE
	POP BC
	POP AF
	RETI

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

	ld hl, $C000		; Read loop
.rd:
	ld a,h
	xor l
	ld b,a
	ld a, [hli]
	cp b
	jr nz, .memfail
	
	ld a, h
	cp $DF
	jr nz, .rd
	ld a, l
	cp $80
	jr nz, .rd
	
	ld hl, testokstr	; Say we're OK
	call puts
	ret
.memfail:			; Say we failed (sadface)
	; decrement hl the easy way
	dec [hl]
	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
	and $0F
	add $30
	call putc
	pop af
	and $0F
	add $30
	call putc
	ret

; Wait for switches to be flipped on and off again.
waitsw:
	ld hl,waitswstr
	call puts
	
	ld hl,$DF82
	ld a, 1
	ld [hl], a

	ld c, $51
	xor a
	ld [c],a
	
.loop1:
	ld a,[c]
	cp $0
	jr z,.loop1
.loop2:
	ld a,[c]
	cp $0
	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
	cp $0
	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
	cp $20
	jr nc,.fail
	ld a, $20
	cp $10
	jr c,.fail
	
	; Test CPL
	ld hl, .cplfail
	ld a, $55
	cpl
	cp $AA
	jr nz,.fail

	; Test DI/EI delay
	di
	ld hl, .dinocausefail
	ld c, $0F	; First, wait until an interrupt happens...
.wait:	ld a, [c]
	and $04
	cp 0
	jr z, .wait
	ei		; Now make sure that an IRQ didn't happen on EI/DI
	di
	ld a, [c]
	and $04
	cp 0
	jr z, .fail
	ld hl, .dicausefail
	ei		; Make sure that an IRQ does happen on EI/NOP/DI
	nop
	nop
	di
	ld a, [c]
	and $04
	cp 0
	jr nz, .fail
	ei
	
	ld hl, .ok
	call puts
	ret
.fail:
	ei
	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
.dinocausefail:
	db "DI/EI does not cause interrupt",0
.dicausefail:
	db "DI/NOP/EI cause interrupt",0
.testfailed:
	db " test failed.",$0D,$0A,0
.ok:
	db "OK!",$0D,$0A,0

; Serial port manipulation functions.
putc:
	ld c, $50
	push af
.waitport:
	ld a,[c]
	cp $00
	jr nz,.waitport
	pop af
	ld [c],a
	ret

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