dave.w.turner@gmail.com wrote:
> Oh, and also, if you are storing currently recieved bits in W, make
> sure you don't use W for anything else which might clear it before you
> put it in memory - some instructions use W without telling you, I
> think.

Uhhh, WHICH instructions would that be?

And it's pretty hard to move -any- data on the PIC without
going through W.

The one notable instruction that has 'funny' behaviour
is CLRW. As coded, it reads whatever INDF is pointing to,
and if that happens to be PORTB your int-on-change gets messed
up. (Ask me how I know about this little GOTACH!)

And speaking of opcodes, has anyone found any useful 'hidden' op codes?
e.g. NOP is listed as 00 0000 0xx0 0000 for 16 series parts.
If you look at the bit pattern you see that it looks
like a movwf, with W as the destination (movww) and 0
for file register.

The ICE2k uses 61 as 'breakpoint'
                       00 0000 0110 0001
For comparison
CLRWDT                00 0000 0110 0100
SLEEP                 00 0000 0110 0011
so there are sure to be other functional opcodes in 006x block,
not that they're useful. The Z80 had quite a number
of 'hidden' opcodes that did useful things, although there
was no guarantee that those codes would work on different
revisions.

Just something to tinker with...

Robert

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