Tony

        I solved the problem by using portb for input and porta for output.  tha
t way
I can rrf for the first bit and rlf for the other three.  AAAchzoooo!  Damn ther
e goes
the level one environment!!!

Scott

Tony Nixon wrote:

> Scott wrote:
> >
> > It seems to be working pretty well now, however when I use the rlf instructi
on
> > the data is rolled into the high nibble of the variable temp and the carry n
ever
> > sees is.  How can I make the temp variable four bits wide?    Thanks for hav
ing
> > mercy on such a newbi.
>
> I think someone sneezed on the wafer before they cut it up and wrapped
> the bits in prickly plastic. It's given your chip an extra instruction
> :-)
>
> The carry is always changed after a 'rrf' or rlf' instruction. It may
> not appear to get changed, because the new data bit may be the same as
> the old.
>
> if PortA = 00000010, then
>
>         movf porta,w
>         movwf temp
>
> temp = 00000010
> carry could be 0 or 1 - it doesn't matter
>
>         rrf temp
>
> temp = 00000001 - [note: bit 7 is the original carry bit value and could
> be 1]
> carry = 0       - carry = original value of temp bit 0
>
> carry = 0 -> key #1 not pressed, loop back and rotate again
>
>         rrf temp
>
> temp = 00000000 - bit 7 = the carry bit value
> carry = 1       - carry = original value of temp bit 0
>
> carry = 1 -> key #2 is pressed, service the key routine
>
> Just looking over your message again, you mentioned "rlf" not "rrf". If
> you changed this by accident that could be causing your problem.
>
> Try using 55h or 0xAA in a register and rotate that left or right to see
> the effect on the register and the carry bit.
>
> --
> Best regards
>
> Tony
>
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