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https://github.com/sehugg/8bitworkshop.git
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90 lines
2.3 KiB
Plaintext
90 lines
2.3 KiB
Plaintext
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processor 6502
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include "vcs.h"
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include "macro.h"
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include "xmacro.h"
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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seg.u Variables
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org $80
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Temp .byte
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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seg Code
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org $f000
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Start
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CLEAN_START
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lda #0
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sta Temp
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NextFrame
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VERTICAL_SYNC
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TIMER_SETUP 37
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inc Temp
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TIMER_WAIT
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TIMER_SETUP 213
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lda Temp
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and #$7f
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jsr WaitForScanline
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sta COLUBK
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lda #180
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jsr WaitForScanline
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lda #0
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sta COLUBK
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lda #192
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jsr WaitForScanline
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jmp TimerDone
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TimerDone
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lda #0
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sta COLUBK
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TIMER_SETUP 30
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TIMER_WAIT
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jmp NextFrame
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align $10
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WaitForScanline subroutine
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ldy INTIM ; Fetch timer value
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.Wait
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cpy INTIM
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beq .Wait ; Wait for it to change
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sta WSYNC ; Sync with scan line
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cmp Timer2Scanline,y
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bcs WaitForScanline
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rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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align $100
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Timer2Scanline
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.byte 215, 0,214,213,212,211,210, 0,209,208,207,206,205,204, 0,203
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.byte 202,201,200,199, 0,198,197,196,195,194, 0,193,192,191,190,189
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.byte 188, 0,187,186,185,184,183, 0,182,181,180,179,178, 0,177,176
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.byte 175,174,173,172, 0,171,170,169,168,167, 0,166,165,164,163,162
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.byte 0,161,160,159,158,157,156, 0,155,154,153,152,151, 0,150,149
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.byte 148,147,146, 0,145,144,143,142,141,140, 0,139,138,137,136,135
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.byte 0,134,133,132,131,130, 0,129,128,127,126,125,124, 0,123,122
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.byte 121,120,119, 0,118,117,116,115,114, 0,113,112,111,110,109,108
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.byte 0,107,106,105,104,103, 0,102,101,100, 99, 98, 0, 97, 96, 95
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.byte 94, 93, 92, 0, 91, 90, 89, 88, 87, 0, 86, 85, 84, 83, 82, 0
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.byte 81, 80, 79, 78, 77, 76, 0, 75, 74, 73, 72, 71, 0, 70, 69, 68
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.byte 67, 66, 0, 65, 64, 63, 62, 61, 60, 0, 59, 58, 57, 56, 55, 0
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.byte 54, 53, 52, 51, 50, 0, 49, 48, 47, 46, 45, 44, 0, 43, 42, 41
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.byte 40, 39, 0, 38, 37, 36, 35, 34, 0, 33, 32, 31, 30, 29, 28, 0
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.byte 27, 26, 25, 24, 23, 0, 22, 21, 20, 19, 18, 0, 17, 16, 15, 14
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.byte 13, 12, 0, 11, 10, 9, 8, 7, 0, 6, 5, 4, 3, 2, 0, 1
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Epilogue
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org $fffc
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.word Start
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.word Start
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