Logix5000 sbutract block

I have a subrtract block in a PLC5000 that is acting differently than I thought it would. I am subtracting a 1 in source A from a float F23:11 in source B. The first time the rung actuates, I subtract 1 from 150 and the result is -149. The next time the rung goes true, I subtract 1 from -149 and get 150. Did I miss something? The help file says that floats are ok to use, is there something I need to do to keep the negative flag from coming on?

1-150=-149
1-(-149)=150

I think you have your parameters reversed.

Yup

Ok, sometimes just when a guy thinks he's getting really smart, he does something to prove that he isn't. Thanks.

Russ