NES Hello World code

Includes iNES and UNIF linkage.

platform/nes/demo/hello_chr.oph

@@ -0,0 +1,20 @@
+;; NES "Hello World" character tables
+
+;; We spell out "Hello World" and we make sure that the colors are
+;; different so our palette shift works.
+
+.text
+.org	$0000
+.byte	$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+.byte	$c6,$c6,$c6,$fe,$c6,$c6,$c6,$00,$00,$00,$00,$00,$00,$00,$00,$00	; H (color 1) #1
+.byte	$00,$00,$00,$00,$00,$00,$00,$00,$fe,$c0,$c0,$fc,$c0,$c0,$fe,$00	; E (color 2) #2
+.byte	$60,$60,$60,$60,$60,$60,$7e,$00,$60,$60,$60,$60,$60,$60,$7e,$00	; L (color 3) #3
+.byte	$60,$60,$60,$60,$60,$60,$7e,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; L (color 1) #4
+.byte	$00,$00,$00,$00,$00,$00,$00,$00,$7c,$c6,$c6,$c6,$c6,$c6,$7c,$00 ; O (color 2) #5
+.byte	$c6,$c6,$d6,$fe,$fe,$ee,$c6,$00,$c6,$c6,$d6,$fe,$fe,$ee,$c6,$00 ; W (color 3) #6
+.byte	$7c,$c6,$c6,$c6,$c6,$c6,$7c,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; O (color 1) #7
+.byte	$00,$00,$00,$00,$00,$00,$00,$00,$fc,$c6,$c6,$fc,$d8,$cc,$c6,$00 ; R (color 2) #8
+									; L (color 3) #3
+.byte	$f8,$cc,$c6,$c6,$c6,$cc,$f8,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; D (color 1) #9
+
+.advance $2000	; Fill in the rest of the CHR-ROM chip.

platform/nes/demo/hello_ines.oph

@@ -0,0 +1,5 @@
+; iNES header
+.byte $4e,$45,$53,$1a,$01,$01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+
+.include "hello_prg.oph"
+.include "hello_chr.oph"

platform/nes/demo/hello_prg.oph

@@ -0,0 +1,162 @@
+;; PRG-ROM for our NES demo program.
+
+.alias	sprites	$200	; Keep our OAM DMA here.
+
+.data
+.org	$0000
+.space	count	1
+.space	palette 32
+
+.text
+.org	$C000
+
+reset:	sei
+	cld
+	; Wait two VBLANKs.
+*	lda	$2002
+	bpl	-
+*	lda	$2002
+	bpl	-
+
+	; Disable all graphics.
+	lda	#$00
+	sta	$2000
+	sta	$2001
+
+	; Mask out sound IRQs.
+	lda	#$40
+	sta	$4017
+
+	; Clear out RAM.
+	lda	#$00
+	ldx	#$00
+*	sta	$000,x
+	sta	$100,x
+	sta	$200,x
+	sta	$300,x
+	sta	$400,x
+	sta	$500,x
+	sta	$600,x
+	sta	$700,x
+	inx
+	bne	-
+
+	; Reset the stack pointer.
+	ldx	#$FF
+	txs
+
+	; Clear the name tables.
+	lda	#$24
+	sta	$2006
+	ldy	#$00
+	sty	$2006
+	ldx	#$08
+	lda	#0
+	ldy	#0
+*	sta	$2007
+	iny
+	bne	-
+	dex
+	bne	-
+
+	; Load the palette from later on in the ROM.
+	lda	#$3F
+	ldx	#$00
+	sta	$2006
+	stx	$2006
+*	lda	palette'rom,x
+	sta	palette,x
+	sta	$2007
+	inx
+	cpx	#$20
+	bne	-
+
+	; Load the proper sprite data into place.
+	ldx	#$00
+*	lda	graphics,x
+	sta	sprites,x
+	inx
+	bne	-
+
+	lda	#$1E
+	sta	count	; Update twice a second
+
+	; Un-scroll everything, just to be safe.
+	lda	#$00
+	sta	$2006
+	sta	$2006
+	sta	$2005
+	sta	$2005
+	; Re-enable the displays.
+	lda	#$80
+	sta	$2000
+	lda	#$1E
+	sta	$2001
+
+	; FINALLY. We've set up the system. From here on it's all up to
+	; the NMI interrupt to handle things.
+	cli
+*	jmp	-
+
+vblank:	; Refresh the SPR-RAM.
+	lda	#$02
+	sta	$4014
+
+	; Time to update the palette?
+	dec	count
+	bne	irq	; If not, done.
+
+	lda	#$1E
+	sta	count	; Update twice a second
+
+	; Update those parts of the palette that aren't transparent.
+	ldx	#$11
+*	txa
+	and	#$03
+	beq	+	; Don't update transparents
+	jsr	bump'palette
+*	inx
+	cpx	#$20
+	bne	--
+
+	; Now re-blast that palette to VRAM.
+	lda	#$3F
+	ldx	#$00
+	sta	$2006
+	stx	$2006
+*	lda	palette,x
+	sta	$2007
+	inx
+	cpx	#$20
+	bne	-
+
+	; And reset the name tables.
+	lda	#$00
+	sta	$2006
+	sta	$2006
+	sta	$2005
+	sta	$2005
+
+irq:	rti
+
+bump'palette:
+	inc	palette,x
+	lda	palette,x
+	and	#$0F
+	sec
+	sbc	#$0D
+	bpl	bump'palette
+	rts
+
+palette'rom:
+	.byte $0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d,$0d
+	.byte $0d,$01,$02,$03,$0d,$04,$05,$06,$0d,$07,$08,$09,$0d,$0a,$0b,$0c
+
+graphics:
+	.byte $70,$01,$00,$6c,$70,$02,$00,$74,$70,$03,$00,$7c,$70,$04,$01,$84
+	.byte $70,$05,$01,$8c
+	.byte $78,$06,$01,$6c,$78,$07,$02,$74,$78,$08,$02,$7c,$78,$03,$02,$84
+	.byte $78,$09,$03,$8c
+
+.advance $FFFA
+	.word vblank, reset, irq

platform/nes/demo/hello_unif.oph

@@ -0,0 +1,24 @@
+.byte "UNIF"
+.dword 7
+.advance $20
+.byte "MAPR"
+.dword ++-+
+*
+.byte "NES-NROM-256",0
+*
+.byte "NAME"
+.dword ++-+
+*
+.byte "Ophis Hello World Demo",0
+*
+.byte "PRG0"
+.dword $4000
+.include "hello_prg.oph"
+
+.byte "MIRR"
+.dword 1
+.byte 0
+
+.byte "CHR0"
+.dword $2000
+.include "hello_chr.oph"