Hi! I am trying to design a calculator circuit that adds 2 four bit 2's complement binary number as its input that outputs an 8 bit 2's complement number when the control bit comes 01.
Here's what I have done so far using a software called Logisim. I am really stuck when I found out that I cannot put the other 4 output buttons(colored in blue in my full adder. I am stumped on how to approach this problem now.
I have tested a few 2's complement and got the output I wanted and some 2's complement number that did not go so well like (having 0100 as the first input and 0110 as the second input did not give me 1010 but gave me 1011.
Here's what I have done so far using a software called Logisim. I am really stuck when I found out that I cannot put the other 4 output buttons(colored in blue in my full adder. I am stumped on how to approach this problem now.
I have tested a few 2's complement and got the output I wanted and some 2's complement number that did not go so well like (having 0100 as the first input and 0110 as the second input did not give me 1010 but gave me 1011.