use Binary adder as subtractor

[yans123]

Hi ,

I created ppa 8 bit adder (simulation) and now I want to use it
as comparator (=~ subtractor).
I know that the logic equation for subtractor is: S=A+B'+1.
in my adder I have carry in bit. can I use it to be the "+1" , in the subtraction equation?

Thanks...

 

[lostinxlation]

Yes you can.

 

[yans123]

OK ...
I tried it. when I did the "+1" in Cin it didn't work fine( wrong values) .
When i tried it with different adders it worked fine.