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