two’s complement

I have searched the manual and this forum for the two’s complement command. I guess I can't find it or there is none.

So will this do it?

Code:

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CHKSUM = (CHKSUM REV7)+1

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Or is there a way I have not found?

There are a couple ways to work with 2's compliment numbers.
"2's compliment" is simply a way to store positive and negative numbers.

You can can change a number to a positive value when it's either positive or negative using the ABS (Absolute Value) function.

PosValue = ABS MyValue

Or, a value can be inverted ... made positive if it's negative, or negative if it's positive using the negative sign.

InvValue = -(MyValue)

That is the same as complimenting the bits and adding 1.
Which can also be done with the bitwise NOT operator (+1).

InvValue = ~(MyValue) + 1

Ok, thanks Darrel, I will use the last 1. It just looks cool!