Hi everyone! I've got 2 full adder-subtractors in front of me, both work, but in different ways. Both add in the same way, but when it comes to substraction they subtract different.
My 2 bits full adder-subtractor is done exactly like this one
where it says there is a problem with the borrow bit at the end.
Here aswell tells us that there's a problem at the end. 12:30
https://www.academia.edu/4020322/DE...OR_COMPOSITE_UNIT_USING_2_S_COMPLEMENT_METHOD
And the second one, made by my roomate, works with no problem at all even at subtraction. The question is, why don't we use the second version? Take a look at his circuit below.
when p is 0 ,subtracts, 1 adds
My 2 bits full adder-subtractor is done exactly like this one
Here aswell tells us that there's a problem at the end. 12:30
https://www.academia.edu/4020322/DE...OR_COMPOSITE_UNIT_USING_2_S_COMPLEMENT_METHOD
And the second one, made by my roomate, works with no problem at all even at subtraction. The question is, why don't we use the second version? Take a look at his circuit below.
when p is 0 ,subtracts, 1 adds
