Sorry Scott, you were indeed right with your code!
I did understand the xor storage of the dif and the
recovery associated.
Thanks again! :o)
-Roman


Scott Dattalo wrote:
>
> On Wed, 21 Aug 2002, Roman Black wrote:
> >
> > Actually it is. You store the new pins in an XORed
> > form. :o) But there is a problem that your code below
> > still takes 9 cycles (once goto is included).
>
> <snip>
>
> Maybe I don't follow. This is what I meant:
>
> pwm_loop
>
>                                 ; first output current1 to motor
>         movf current1,w         ; get currents and phase switching
>         movwf PORTB             ; send to motor!
>
>         movf  diff,w            ;
>         xorwf inputs_last       ;
>
>         ;-------------------------
>                                 ; now output current2
>         movf current2,w         ;
>         movwf PORTB             ; send to motor!
>
> ;        nop                     ; let ports settle
> ;        nop                     ; + some delay
>
>         movf  inputs_last,w     ; now test input pins
>         xorwf PORTA,w
>         movwf diff
>
>         skpnz
>          goto pwm_loop          ; z, inputs not changed, so keep looping
>         ;-------------------------------------------------
>
> That has the 4/8 cycle requirement.  There's a trick to squeeze in another
> instruction and still meet the timing. It's probably obvious, so I won't
> bother mentioning it. :)

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