Updated again.
---
James Newton (PICList Admin #3)
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-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Scott Dattalo
Sent: Wednesday, April 11, 2001 15:52
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: 16-bit 16c7xx comparison code


On Wed, 11 Apr 2001, M Core wrote:

> Hi Scott,
>   Just looking at that code again - I'm not sure now that your incfsz will
> even fix it. For example if you have the number:
>
> x0201 = X and xff02 = Y
> then we will get to the incfsz point in the code and
> the ff MSB will be incremented to 0, and the subtraction is skipped,
> then it checks the C bit - which the incfsz instruction does not set - so
> there is still problems with that code because the C bit is set from the
LSB
> previous subtraction still, but we are looking at the MSB now...


Sigh, there are two mistakes (so far) in that snippet.

         ;XH:XL  YH:YL

           movf    yl,w
           subwf   xl,w
           movf    yh,w
           skpc          ;(was skpz)
            incfsz yh,w  ;(was incf)
             subwf xh,w

           skpnc
            goto   x_is_greater_than_or_equal_to_y

There are 8 instructions, so there may be 6 more mistakes!

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