Hello PICLIST,

 I found one delay routine in which I think it has errors

 the code and explanation is here

 http://techref.massmind.org/techref/piclist/weedfreq.htm

 I have one question for this part of code from WCT5.ASM:

;
int_del movlw   0x05            ;delay 5.000 ms (4 MHz clock)
        movwf   count1
d1      movlw   0xA5
        movwf   count2
d2      decfsz  count2  ,f
        goto    d2
        decfsz  count1  ,f
        goto    d1
        retlw   0x00

Why in comment it is said that this delay is 5 ms while actually it is
2.5ms ?

I make my one calculation here it is (processor cycles is in '()' ):

int_del movlw   0x05        (1)
        movwf   count1      (1)

        ;494 + 2
d1      movlw   0xA5        (1)
        movwf   count2      (1)

        ;this is for 3 cycles * 0xA5(165) = 495 -1 -this is for last
        ;iteration
d2      decfsz  count2  ,f  (1) (2)
        goto    d2          (2)  |

        ;494 + 2 + 3   = 499
        decfsz  count1  ,f  (1) (2)
        goto    d1          (2)  |

        ;499 * 5 -1 (for last iteration) =
        ;2494 + 2(first two instruction) + 2(return) = 2498
        retlw   0x00        (2)

if we add 2 for call of this delay function the processor cycles are
2500 * 1000uS = 2.500 ms not 5.000 ms !

If I'm wrong please say to me what I do wrong in my calculation.


--
Best regards,
 Ivan                          mailto:i_dachev@prosyst.bg

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