Proworx 32 Simple Question

[Galaniz]

I have another simple question. This time it is in regards to Proworx use of signed and unsigned integers in the SUB function. The modicon manual states "

The SUB instruction performs a signed or unsigned 16-bit subtraction (value 1 -
value 2) on the top and middle node values, then posts the signed or unsigned​

difference in a 4x holding register in the bottom node."

How is it determined if the output will be signed or unsigned. I uploaded a program with a SUB instruction. The top register is 40100 (set to 92 in register editor) middle is register 40108 (set to 275) and the bottom is 40116 (reads 183). The radix is set to decimal for all and when I changed the radix to signed for 40116 it was still positive 183. How would I set the output to read negative or is there something I am missing. I am converting over to compactlogix so if the SUB is actually subtracting and taking the absolute value I would like to figure that out now.

Thanks
Gabriel

 

[TConnolly]

In a 984LL program you would need to check the output of the lower node on the block. If the output is passing power then the result is negative. However, the register will contain the absolute value of the result.

 

[Mickey]

And from a manual I have.

 

[TConnolly]

Do you need an instruction reference manual?

 

[Galaniz]

Thank you all for the quick replies. Sometimes I get caught up work and don't make time to reply, but the answers were what i needed.