slightly improve sys.waitvsync() on c64

2025-02-26 11:29:24 +00:00 · 2021-10-03 21:35:12 +02:00 · 2021-10-03 21:35:12 +02:00 · 06b3bf27b5
commit 06b3bf27b5
parent fbef63e150
1 changed files with 3 additions and 5 deletions
--- a/compiler/res/prog8lib/c64/syslib.p8
+++ b/compiler/res/prog8lib/c64/syslib.p8
@ -502,11 +502,9 @@ sys {
        ; --- busy wait till the next vsync has occurred (approximately), without depending on custom irq handling.
        ;     note: a more accurate way to wait for vsync is to set up a vsync irq handler instead.
        %asm {{
-           lda  c64.RASTER
-            beq  -
-           lda  c64.RASTER
-            bne  -
-            bit  c64.SCROLY
+-           bit  c64.SCROLY
+            bpl  -
+-           bit  c64.SCROLY
            bmi  -
            rts
        }}