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41 lines
1001 B
ArmAsm
41 lines
1001 B
ArmAsm
;
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; clock_t clock (void);
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;
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.constructor initclock
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.export _clock
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.forceimport ticktock ; make sure that tickcount changes
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.importzp tickcount, sreg
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; Make the process clock start at zero.
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.segment "ONCE"
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initclock:
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ldx #4 - 1
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@lp: stz tickcount,x
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dex
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bpl @lp
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rts
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; ------------------------------------------------------------------------
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.code
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; This function might be interrupted while it is reading the several bytes of
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; the clock. They are read again if that happens. (We do not want to stop
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; interrupts because that might cause glitches in interrupt-driven graphics
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; and sound.)
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.proc _clock
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lda tickcount
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ldy tickcount+3
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sty sreg+1
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ldy tickcount+2
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sty sreg
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ldx tickcount+1
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cmp tickcount
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bne _clock ; clock changed; reread it
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rts
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.endproc
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