1
0
mirror of https://github.com/sehugg/8bitworkshop.git synced 2024-12-23 18:31:08 +00:00
8bitworkshop/presets/nes/helloworld.asm

226 lines
5.1 KiB
NASM

include "nesdefs.asm"
;;;;; ZERO-PAGE VARIABLES
seg.u Zeropage
org $0
RLEPtr word
Temp1 byte
NES_HEADER 0,2,1,0 ; mapper 0, 2 PRGs, 1 CHR, horizontal
Start:
NES_INIT ; set up stack pointer, turn off PPU
jsr WaitSync
jsr WaitSync ;wait for PPU warmup
jsr ClearRAM ;clear CPU memory
jsr ClearVRAM ;set PPU RAM
jsr SetPalette ;set colors
lda #0
sta PPU_ADDR
sta PPU_ADDR ;PPU addr = 0
sta PPU_SCROLL
sta PPU_SCROLL ;scroll = 0
lda #$90
sta PPU_CTRL ;enable NMI
lda #$1e
sta PPU_MASK ;enable rendering
.endless
jmp .endless ;endless loop, NMI only
; fill video RAM
ClearVRAM: subroutine
lda #$20
sta PPU_ADDR
lda #$00
sta PPU_ADDR ; PPU addr = $2000
tax ; X = 0 (inner loop)
ldy #8 ; Y = 8 (outer loop)
lda #$2f ; A = value to write to VRAM
.loop:
sta PPU_DATA
inx
bne .loop ; repeat 256 times
dey
bne .loop ; repeat 8 times
rts
; set palette colors
SetPalette: subroutine
ldy #$00
lda #$3f
sta PPU_ADDR
sty PPU_ADDR
ldx #32
.loop:
lda Palette,y
sta PPU_DATA
iny
dex
bne .loop
rts
; load RLE-compressed data to VRAM
WriteRLE: subroutine
sta RLEPtr
sty RLEPtr+1
.nextspan
ldy #0
lda (RLEPtr),y ; length
beq .done
tax ; X = length in bytes
iny
lda (RLEPtr),y ; lo byte
pha
iny
lda (RLEPtr),y ; hi byte
sta PPU_ADDR ; write hi byte
pla
sta PPU_ADDR ; write lo byte
jsr RLEDoText
tya
sec ; + 1 (we didn't iny on last loop)
adc RLEPtr ; add Y to RLEPtr
sta RLEPtr
bcc .nextspan ; no overflow
inc RLEPtr+1
bne .nextspan ; branch almost always taken
.done
rts
; translate ASCII to tiles and copy to VRAM
RLEDoText:
iny
lda (RLEPtr),y ; hi byte
stx Temp1
sec
sbc #$20
tax
lda ASCII2Tile,x
ldx Temp1
sta PPU_DATA
dex
bne RLEDoText
rts
ASCII2Tile:
hex 2f242d2b 252d2d29 2d2d2d2d 2a27282d ; 20
hex 00010203 04050607 08092600 00000000 ; 30
hex 2f0a0b0c 0d0e0f10 11121314 15161718 ; 40
hex 191a1b1c 1d1e1f20 2122232d 2d2d2d2c ; 50
;;;;; COMMON SUBROUTINES
include "nesppu.asm"
;;;;; INTERRUPT HANDLERS
NMIHandler: subroutine
lda #<HelloWorld
ldy #>HelloWorld
jsr WriteRLE ;write "hello world" message
; restore PPU
lda #0
sta PPU_ADDR
lda #0
sta PPU_ADDR
rti
;;;;; CONSTANT DATA
Palette:
hex 1f ;background
hex 0909191f ;bg0
hex 0909191f ;bg1
hex 0909191f ;bg2
hex 0909191f ;bg3
hex 14243400 ;sp0
hex 15253500 ;sp1
hex 16263600 ;sp2
hex 17273700 ;sp3
HelloWorld:
byte 12
word $2000 + (32*12) + 11
byte "HELLO WORLD!"
byte 32
word $2041
byte "ABCDEF0123456789"
byte "$!:-.',#_ "
byte 0
;;;;; CPU VECTORS
NES_VECTORS
;;;;; TILE SETS
org $10000
; OAM (sprite) pattern table
REPEAT 256
hex 00000000000000000000000000000000
REPEND
; background (tile) pattern table
REPEAT 5
;;{w:8,h:8,bpp:1,count:48,brev:1,np:2,pofs:8,remap:[0,1,2,4,5,6,7,8,9,10,11,12]};;
hex 7e42424646467e007e42424646467e00
hex 08080818181818000808081818181800
hex 3e22023e30303e003e22023e30303e00
hex 3c24041e06263e003c24041e06263e00
hex 4444447e0c0c0c004444447e0c0c0c00
hex 3c20203e06263e003c20203e06263e00
hex 3e22203e26263e003e22203e26263e00
hex 3e020206060606003e02020606060600
hex 3c24247e46467e003c24247e46467e00
hex 3e22223e060606003e22223e06060600
hex 3c24247e626262003c24247e62626200
hex 7c44447e62627e007c44447e62627e00
hex 7e42406060627e007e42406060627e00
hex 7e42426262627e007e42426262627e00
hex 7c40407c60607c007c40407c60607c00
hex 3c20203c303030003c20203c30303000
hex 7e42406e62627e007e42406e62627e00
hex 4242427e626262004242427e62626200
hex 10101018181818001010101818181800
hex 0404040606467e000404040606467e00
hex 4444447e626262004444447e62626200
hex 2020203030303e002020203030303e00
hex fe9292d2d2d2d200fe9292d2d2d2d200
hex 7e424262626262007e42426262626200
hex 7e46464242427e007e46464242427e00
hex 7e42427e606060007e42427e60606000
hex 7e424242424e7e007e424242424e7e00
hex 7c44447e626262007c44447e62626200
hex 7e42407e06467e007e42407e06467e00
hex 7e101018181818007e10101818181800
hex 4242426262627e004242426262627e00
hex 646464642c2c3c00646464642c2c3c00
hex 4949494969697f004949494969697f00
hex 4242423c626262004242423c62626200
hex 4242427e181818004242427e18181800
hex 7e42027e60627e007e42027e60427e00
hex 10101818180018001010181818001800
hex 187e407e067e1800187e407e067e1800
hex 00180018180000000018001818000000
hex 00003c3c0000000000003c3c00000000
hex 00000018180000000000001818000000
hex 18180810000000001818081000000000
hex 00000018180810000000001818081000
hex 7c7c7c7c7c7c7c007c7c7c7c7c7c7c00
hex 0000000000007c000000000000007c00
hex 00000000000000000000000000000000
hex 00000000000000000000000000000000
hex 00000000000000000000000000000000
;;
REPEND
REPEAT 15
hex 00000000000000000000000000000000
REPEND
hex 00000000000000000000000000000000