I need to check that a value, which will be a slightly variable code value,
is between an upper and a lower threshold (or not).

The way I have thought of doing it is to subtract it from the upper
threshold and retain the result, then subtract the lower threshold from it
and retain that result. If the two results are positive then the code is
within the limits and is good but if either are less than zero then the code
is no good.

        _______________________ upper threshold



                code value


        _______________________ lower threshold


Here is my problem: How do I check for a <0 (negative) value in a PIC register?

Does anybody know? Is it possible? If not what am I going to do?

Later,

Desperate Steve.