cc65/libsrc/atari/clock.s

;
; Piotr Fusik, 04.11.2001
; originally by Ullrich von Bassewitz and Sidney Cadot
;
; clock_t clock (void);
; unsigned _clocks_per_sec (void);
;

	.export		_clock, __clocks_per_sec
	.importzp	sreg

	.include	"atari.inc"


.proc	_clock

	ldx	#5		; Synchronize with Antic, so the interrupt won't change RTCLOK
	stx	WSYNC		; while we're reading it. The synchronization is done same as
@L1:	dex			; in SETVBLV function in Atari OS.
	bne	@L1
	stx	sreg+1		; Byte 3 is always zero
	lda	RTCLOK+2
	ldx	RTCLOK+1
	ldy	RTCLOK
	sty	sreg
	rts

.endproc


.proc	__clocks_per_sec

	lda	PAL		; use hw register, PALNTS is only supported on XL/XE ROM
	and	#$0e
	bne	@NTSC
	tax
	lda	#50
	rts
@NTSC:	ldx	#0
	lda	#60
	rts

.endproc