I have been on this list for about 6 years, I think, and am
working on my first actual PIC program.  One of the things I
discovered that kind of surprised me was the lack of any instructions
that can test to see if some value is => or < some other value.
Testing to see if 2 values are exactly equal is easy with the xorwf
instruction because the result is 0 if the two values are the same.

        It finally hit me that what I could do is to take the value
I am testing against, get the 2's compliment by xorwf'ing it with 0xff
and then adding 1, and then taking that value to add to the unknown
value to see if the carry sets.  If it sets, the unknown value was =
or > the test value.

        This works fine, but am I missing something more simple?

        My previous assembler coding has been in the Motorola 68HC11,
8086, and 6502 assemblers.  There are instructions that branch on
carry set or clear and the status of the Z flag as well as some
branches that work on signed arithmetic and others that work on
unsigned values.

        I realized that the PIC instructions do exactly the same
thing, but the details are more visible.

        There is nothing like actually getting in there and designing
a project to let one really learn the instruction set.

Martin McCormick WB5AGZ  Stillwater, OK
OSU Center for Computing and Information Services Data Communications Group