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Brooke Vibber 2022-12-11 16:37:47 -08:00
parent cf2a18e0d7
commit 0bae8670ba
1 changed files with 7 additions and 4 deletions
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dither4.s
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@ -209,6 +209,10 @@ wait_loop:
.macro run_frame frame_offset .macro run_frame frame_offset
.scope .scope
; each scanline is 228 color clocks
; that's 114 CPU cycles
; minus 41-43 for DMA leaves 71-73 clock cycles per line
each_scanline_pair: each_scanline_pair:
sty scanline ; 3 cycles sty scanline ; 3 cycles
inner_scanline frame_offset, 0 ; 23-26 cycles before break, 12 cycles after inner_scanline frame_offset, 0 ; 23-26 cycles before break, 12 cycles after
@ -219,15 +223,14 @@ wait_loop:
ldy scanline ; 3 cycles ldy scanline ; 3 cycles
inner_scanline frame_offset, 128 ; 23-26 cycles before break, 12 cycles after inner_scanline frame_offset, 128 ; 23-26 cycles before break, 12 cycles after
; save for later lookup ; pair cleanup: 6 cycles
ldy VCOUNT ; 4 cycles ldy VCOUNT ; 4 cycles
cpy #0 ; 2 cycles
bne each_scanline_pair ; 2 cycles bne each_scanline_pair ; 2 cycles
; frame cleanup: 11 cycles
lda frame_counter ; 3 cycles lda frame_counter ; 3 cycles
eor #1 ; 2 cycles eor #1 ; 2 cycles
sta frame_counter ; 3 cycles sta frame_counter ; 3 cycles
jmp wait_start ; 3 cycles jmp wait_start ; 3 cycles
.endscope .endscope
.endmacro .endmacro