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.export _waitvcount
.include "atari.inc"
; wait for VCOUNT to reach a particular value. Use this
; to avoid updating parts of the screen while ANTIC is
; reading from it.
; c should be ((4 + Yposition) * 4), where Yposition is
; the text line below the bottom one you're about to modify.
; void __fastcall__ waitvcount(unsigned char *c)
_waitvcount:
sta FR1
w:
lda VCOUNT
cmp FR1
bne w
STA WSYNC ; finish current scanline
rts
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