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22 lines
491 B
ArmAsm
22 lines
491 B
ArmAsm
;
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; 2020-01-08, Greg King
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;
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; void waitvsync (void);
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; /* Wait for the start of the next video field. */
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;
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; VERA's vertical sync causes IRQs which increment the jiffy timer.
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;
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.export _waitvsync
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.include "cx16.inc"
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_waitvsync:
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ldx VIA1::PRA ; (TIMER is in RAM bank 0)
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stz VIA1::PRA
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lda TIMER + 2
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: cmp TIMER + 2
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beq :- ; Wait for next jiffy
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stx VIA1::PRA
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rts
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