mirror of
https://github.com/cc65/cc65.git
synced 2024-06-07 07:29:33 +00:00
22 lines
491 B
ArmAsm
22 lines
491 B
ArmAsm
;
|
|
; 2020-01-08, Greg King
|
|
;
|
|
; void waitvsync (void);
|
|
; /* Wait for the start of the next video field. */
|
|
;
|
|
; VERA's vertical sync causes IRQs which increment the jiffy timer.
|
|
;
|
|
|
|
.export _waitvsync
|
|
|
|
.include "cx16.inc"
|
|
|
|
_waitvsync:
|
|
ldx VIA1::PRA ; (TIMER is in RAM bank 0)
|
|
stz VIA1::PRA
|
|
lda TIMER + 2
|
|
: cmp TIMER + 2
|
|
beq :- ; Wait for next jiffy
|
|
stx VIA1::PRA
|
|
rts
|