2 bit adder subtractor

[waheeda]

hi to all !!i am given a project to make a 2 bit processor which does only addition and subtraction...i know half adder and sub tractor ,but making them together is kinda difficult 4 me,,because i have never made them. could u please help me how to make it in work bench..any circuit diagram if u have.,

 

[BrownOut]

Maybe this will help. It's a truth table for your adder. ib0 and ib1 are your two inputs. op=0 for addition and op=1 for subtraction. ob0 is the output and carry is, well the carry bit. You can use any method (ie karnaugh maps) to obtain the functions.

[B][U]ib0 ib1 op ob0 carry[/U][/B]
0   0    0   0      0
1   0    0   1      0
0   1    0   1      0
1   1    0   0      1
0   0    1   0      0
1   0    1   0      0
0   1    1   1      1
1   1    1   0      0

 

[BrownOut]

PS: In the future, ask your technical questions in the tech forums or the homework forum for better responses.