git.y1.nz

commit f5d12b3ac77e98604987bcabba4ee1d418efa2e8
parent 5b401021fa12843f09e1bfb7882736fd44543f85
Author: Michel Iwaniec <46843052+michel-iwaniec@users.noreply.github.com>
Date:   Thu, 30 May 2024 23:13:12 +0100

NES: Add simulated increment of _bkg_scroll_y between calls to LCD isr, in case isr does not re-write it (#684)


Diffstat:
M
gbdk-lib/libc/targets/mos6502/nes/crt0.s
4
++++

1 file changed, 4 insertions(+), 0 deletions(-)
diff --git a/gbdk-lib/libc/targets/mos6502/nes/crt0.s b/gbdk-lib/libc/targets/mos6502/nes/crt0.s
@@ -456,6 +456,10 @@ _vsync::
     clc ; -1 to compensate for LCD PPU write taking up a scanline on its own
     sbc *.lcd_scanline_previous
     sta __lcd_isr_delay_num_scanlines,y
+    ; Add number of delayed scanlines to _bkg_scroll_y to simulate PPU increment
+    clc
+    adc *_bkg_scroll_y
+    sta *_bkg_scroll_y
     ; Call LCD isr
     jsr .jmp_to_LCD_isr
     ; Copy shadow registers

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