Apple-2gs-SW/iigs-game-engine
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Copy OAM source on-demand instead of on DMA REG access

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Lucas Scharenbroich 2023-06-30 15:53:43 -05:00
parent 576c402d0b
commit 63d2f0ea46
1 changed files with 11 additions and 5 deletions
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16
demos/smb/ppu.s
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@ -571,6 +571,7 @@ no_pal
; Trigger a copy from a page of memory to OAM. Since this is a DMA operation, we can cheat and do a 16-bit copy ; Trigger a copy from a page of memory to OAM. Since this is a DMA operation, we can cheat and do a 16-bit copy
PPUDMA_WRITE ENT PPUDMA_WRITE ENT
rtl
php php
pha pha
@ -613,24 +614,29 @@ scanOAMSprites
ldy #0 ldy #0
:loop :loop
lda PPU_OAM,x ; Y-coordinate ; lda PPU_OAM,x ; Y-coordinate
ldal ROMBase+$200,x
cmp #max_nes_y+1 ; Skip anything that is beyond this line cmp #max_nes_y+1 ; Skip anything that is beyond this line
bcs :skip bcs :skip
cmp #y_offset cmp #y_offset
bcc :skip bcc :skip
lda PPU_OAM+1,x ; $FC is an empty tile, don't draw it ; lda PPU_OAM+1,x ; $FC is an empty tile, don't draw it
ldal ROMBase+$201,x
cmp #$FC cmp #$FC
beq :skip beq :skip
lda PPU_OAM+3,x ; If X-coordinate is off the edge skip it, too. ; lda PPU_OAM+3,x ; If X-coordinate is off the edge skip it, too.
ldal ROMBase+$203,x
cmp #255-8 cmp #255-8
bcs :skip bcs :skip
rep #$20 rep #$20
lda PPU_OAM,x ; lda PPU_OAM,x
ldal ROMBase+$200,x
sta OAM_COPY,y sta OAM_COPY,y
lda PPU_OAM+2,x ; lda PPU_OAM+2,x
ldal ROMBase+$202,x
sta OAM_COPY+2,y sta OAM_COPY+2,y
sep #$20 sep #$20