main.asm (SNES Homebrew Program)

;== Include MemoryMap, HeaderInfo, and interrupt Vector table ==
.INCLUDE "header.inc"

;== Include Library Routines ==
.INCLUDE "InitSNES.asm"
.INCLUDE "LoadGraphics.asm"

;RAM Usage:
;	$0000 - BG1 (Map) Horizontal Scroll
;	$0001 - BG1 (Map) Vertical Scroll
;	$0002 - BG2 (Checkerboard) Horizontal Scroll
;	$0003 - BG2 (Checkerboard) Vertical Scroll
;	$0004 - Noise On Value

;==========================================
; Main Code
;==========================================

.BANK 0 SLOT 0
.ORG 0
.SECTION "MainCode"

Main:
    InitializeSNES							;Initialize the SNES

    rep #$10								;Set X/Y to 16-bit
    sep #$20								;Set A to 8-bit

	jsl UploadAndExecuteSoundEngine

    LoadPalette BGPalette, 0, 12			;Load the background palette

	LoadPalette BGPalette, 8*16, 12			;Load the background palette

    LoadBlockToVRAM TileData, $0000, TileDataEnd-TileData	;Load the background tiles
	LoadBlockToVRAM LevelData, $0800, $0800					;Load the map to VRAM
	LoadBlockToVRAM CheckerData, $0C00, $0800				;Load the checkerboard to VRAM (A Routine to generate the checkerboard will eventually be used)

	jsl PlaceHud							;Place the text on BG3

    jsr SetupVideo							;Setup video

	lda #$81
	sta $4200								;Enable NMI and Joypad Auto-Read

	lda #$0F
    sta $2100      							; Turn on screen, full Brightness

	jsr MosaicEffect						; Do the mosaic effect

	lda #$00
	sta $0004
	sta $0005

Infinity:
	sep #$20

	lda $4219
	and #$08
	bne @SkipUp
	lda $0001
	inc a
	sta $0001
	lda $0003
	dec a
	sta $0003
@SkipUp:

	lda $4219
	and #$04
	bne @SkipDown
	lda $0001
	dec a
	sta $0001
	lda $0003
	inc a
	sta $0003
@SkipDown:

	lda $4219
	and #$02
	bne @SkipLeft
	lda $0000
	inc a
	sta $0000
	lda $0002
	dec a
	sta $0002
@SkipLeft:

	lda $4219
	and #$01
	bne @SkipRight
	lda $0000
	dec a
	sta $0000
	lda $0002
	inc a
	sta $0002
@SkipRight:

	lda #$00
	sta $2141

	lda $4218
	and #$80
	beq @SkipA

	lda #$01
	sta $2141

@SkipA:

	lda $0004
	inc a
	sta $0004
	sta $2140

@WaitEcho:
	lda $2140
	cmp $0004
	bne @WaitEcho

	rep #$20

	wai				;Wait for interrupt
    jmp Infinity	;Jump to Infinity

;============================================================================
VBlank:
    rep #$30        ; A/mem=16 bits, X/Y=16 bits (to push all 16 bits)
    phb
	pha
	phx
	phy
	phd

	sep #$20		;Set A to 8-bit
	rep #$10		;Set X/Y to 16-bit

    lda $4210       ; Clear NMI flag

	;Sprite Code Start
	ldx #$0000
	stx $2102

	lda $0000
	sta $2104

	lda $0001
	sta $2104

	lda #$31
	sta $2104

	lda #$30
	sta $2104

	lda #$20
	sta $2104

	lda #$30
	sta $2104

	lda $0000
	sta $2104

	lda #$30
	sta $2104

	ldx #$0100
	stx $2102

	lda #$0A
	sta $2104
	;Sprite Code End

	ldx #$0000

	lda $0000		;Load $0002 into A
	sta $210D		;Store A into the low byte of $210D (BG1HOFS)
	stx $210D		;Store X into the high byte of $210D

	lda $0001
	sta $210E		;Store A into the low byte of $210E (BG1VOFS)
	stx $210E		;Store X into the high byte of $210E

	lda $0002
	sta $210F
	stx $210F

	lda $0003
	sta $2110
	stx $2110

	rep #$20		;Set A to 16-bit

	;sep #$10

    pld
	ply
	plx
	pla
	plb

    sep #$30
    rti
;============================================================================

MosaicEffect:
	lda #$FF
	sta $2106
Loop:
	sbc #$10
	sta $2106
	wai
	wai
	wai
	wai
	wai
	wai
	wai
	wai
	cmp #$0F
	bne Loop
	rts

PlaceHud:
	rep #$10
	ldx #$1000
	ldy #$0000
@PlaceHudLoop:
	stx $2116
	lda Text, y
	cmp #$FF
	beq @DonePlacingHud
	sta $2118
	lda #$20
	sta $2119
	inx
	iny
	jmp @PlaceHudLoop
@DonePlacingHud:
	rtl

Text: .db "USE D-PAD TO SCROLL             HOLD A FOR NOISE", $FF

UploadAndExecuteSoundEngine:
	sei			;Disable interrupts

@WaitReady1:
	lda $2140
	cmp #$AA
	bne @WaitReady1
@WaitReady2:
	lda $2141
	cmp #$BB
	bne @WaitReady2	;"Is the SPC700 ready?"

	lda #$01
	sta $2141
	lda #$00
	sta $2142
	lda #$05
	sta $2143
	lda #$CC
	sta $2140		;Send the transfer begin bytes

@WaitEcho1:
	lda $2140
	cmp #$CC
	bne @WaitEcho1	;Wait for PORT0 to echo

	ldx SoundEngineEnd-SoundEngine
	ldy #$0000
@TransferFirst:
	lda SoundEngine, y
	sta $2141		;Write the first byte to PORT1

	lda #$00
	sta $2140		;Write 0 to PORT0

@WaitEcho2:
	lda $2140
	cmp #$00
	bne @WaitEcho2	;Wait for PORT0 to echo

	dex
	iny

@TransferRest:
	lda SoundEngine, y
	sta $2141		;Write the next byte to PORT1

	lda $2140
	inc a
	sta $2140		;Increase the byte in PORT0 and send it back
	sta $0000

@WaitEcho3:
	lda $2140
	cmp $0000
	bne @WaitEcho3

	dex
	iny

	txa
	cmp #$00
	bne @TransferRest

	lda #$00
	sta $2141	;0 in PORT1
	lda #$00
	sta $2142
	lda #$05
	sta $2143	;Execute address in PORT2 and PORT3
	lda $2140
	clc
	adc #$02
	sta $2140	;Increase PORT0 by 2 and store it in PORT0

	stz $0000
	lda #$00
	ldx #$0000
	ldy #$0000

	cli			;Enable interrupts
	rtl

SoundEngine: .incbin "soundEngine.bin"
SoundEngineEnd:

;============================================================================
; SetupVideo -- Sets up the video mode and tile-related registers
;----------------------------------------------------------------------------
; In: None
;----------------------------------------------------------------------------
; Out: None
;----------------------------------------------------------------------------
SetupVideo:

    lda #$09
    sta $2105      ; Set Video mode 1 and BG3 priority bit

    lda #$08
    sta $2107	   ; Set BG1's Tile Map offset to $0800 (Word address)
	lda #$0C
	sta $2108	   ; Set BG2's Tile Map offset to $0C00
	lda #$10
	sta $2109	   ; Set BG3's Tile Map offset to $1000

    lda #$17       ; Enable BG1, BG2, BG3, and OBJ
    sta $212C

    rts

.ENDS
;============================================================================

.BANK 1 SLOT 0
.ORG 0
.SECTION "CharacterData"
TileData:
	.incbin "tiles.chr"
TileDataEnd:

BGPalette:
	;    gggrrrrr   ?bbbbbgg
	.db %00000000, %00000000
	.db %00010000, %01000010
	.db %00001000, %00100001
	.db %11111111, %01111111

	.db %00000000, %00000000
	.db %11111111, %01111111
	.db %00000000, %00000000
	.db %00011111, %00000000

	.db %00000000, %00000000
	.db %11010110, %01111110
	.db %00010000, %01111110
	.db %00001000, %01111101
.ENDS

.SECTION "MapData"
LevelData: .incbin "level1.bin"
CheckerData: .incbin "checker.bin"
.ENDS

;.SECTION "SoundEngine"
;SoundEngine: .incbin "soundEngine.bin"
;SoundEngineEnd:
;.ENDS