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'Polynomial ?'
2000\05\18@211030 by mark

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Hi,

Is there a way to reduce the size of this routine ?

Polynomial  = x0 + x12 + x17

x0 is in "data" bit_0
x12 is in "mid" bit_3
x17 is in "old" bit_0

               rlf     mid,w        ; x12 in w bit_4
               movwf   temp         ; x12 in temp bit_4
               swapf   temp,w       ; x12 in w bit_0
               xorwf   old,w        ; x12 + x17 in w bit_0
               xorwf   data,w       ; x0 + x12 + x17 in w bit_0
               movwf   temp
               rrf     temp,f       ; x0 in Carry

               rlf     new,f        ; x0 to bit_0
               rlf     mid,f        ; Updates x12
               rlf     old,f        ; Updates x17

Thanks for your help.


Marcelo Puhl
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2000\05\19@065221 by Scott Dattalo

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On Thu, 18 May 2000, Marcelo Puhl wrote:

> Hi,
>
> Is there a way to reduce the size of this routine ?

Absolutely!

{Quote hidden}

how 'bout

  rrf    data,w
  rlf    new,f     ;copy data.0
  rlf    mid,f     ;2nd part of 24bit shl

  swapf  mid,w     ;get mid.4 (originally mid.3)
  xorwf  old,w     ;xor'd with old.0
  rlf    old,f     ;complete the 24bit shift

  andlw  1         ;add old.0^mid.3
  xorlw new,f      ;to new.0

Saves a couple of cycles

Scott

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