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