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8bitworkshop/presets/vcs/xmacro.h

33 lines
818 B
C

;-------------------------------------------------------
; Usage: TIMER_SETUP lines
; where lines is the number of scanlines to skip (> 2).
; The timer will be set so that it expires before this number
; of scanlines. A WSYNC will be done first.
MAC TIMER_SETUP
.lines SET {1}
.cycles SET ((.lines * 76) - 13)
; special case for when we have two timer events in a line
; and our 2nd event straddles the WSYNC boundary
if (.cycles % 64) < 12
lda #(.cycles / 64) - 1
sta WSYNC
else
lda #(.cycles / 64)
sta WSYNC
endif
sta TIM64T
ENDM
;-------------------------------------------------------
; Use with TIMER_SETUP to wait for timer to complete.
; Performs a WSYNC afterwards.
MAC TIMER_WAIT
.waittimer
lda INTIM
bne .waittimer
sta WSYNC
ENDM