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Brooke Vibber 2024-09-07 12:12:11 -07:00
parent 8302f2132f
commit 9242ffc4e6
1 changed files with 13 additions and 15 deletions
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dither4.s
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@ -159,25 +159,24 @@ wait_loop:
sta AUDC1 ; 4 cyc
.endmacro
.macro audio_prep
.macro audio_prep ; 8-9 cycles
; Y is VCOUNT at entry
lda (sample_ptr),y ; 5/6 cyc
sta audiotemp ; 3 cyc
.endmacro
; call with A pre-loaded to audiotemp
.macro audio_play_lo
;lda audiotemp ; 3 cyc
and #$0f ; 2 cyc
ora #$10 ; 2 cyc
sta AUDC1 ; 4 cyc
.macro audio_play_lo ; 8 cycles
; A is loaded with packed audio byte at entry
and #$0f ; 2 cyc
ora #$10 ; 2 cyc
sta AUDC1 ; 4 cyc
.endmacro
; clobbers Y
.macro audio_play_hi ; 12 cycles
ldy audiotemp ; 3 cyc
ldy audiotemp ; 3 cyc
lda audio_high_byte,y ; 5 cyc
sta AUDC1 ; 4 cyc
sta AUDC1 ; 4 cyc
.endmacro
.macro audio_inc
@ -216,26 +215,25 @@ wait_loop:
sty scanline ; 3 cycles
inner_scanline frame_offset, 0 ; 23-26 cycles before break, 12 cycles after
ldy scanline ; 3 cycles
audio_prep
audio_play_lo
ldy scanline ; 3 cycles
audio_prep ; 8-9 cycles
audio_play_lo ; 8 cycles
ldy scanline ; 3 cycles
inner_scanline frame_offset, 128 ; 23-26 cycles before break, 12 cycles after
audio_play_hi
audio_play_hi ; 12 cycles
; pair cleanup: 6 cycles
ldy VCOUNT ; 4 cycles
bne each_scanline_pair ; 2 cycles
; Do bookkeeping during vblank!
audio_inc ; 22-32 cycles
; frame cleanup: 11 cycles
lda frame_counter ; 3 cycles
eor #1 ; 2 cycles
sta frame_counter ; 3 cycles
;jmp wait_start ; 3 cycles
jmp each_frame ; 3 cycles
.endscope
.endmacro