# Need some help with a synchronous circuit

1. Sep 28, 2010

### gipc

I'm trying to analyze the following circuit which is pretty basic.
There is the circuit and it's diagram which is the solution:

http://img822.imageshack.us/img822/7291/circuiti.jpg [Broken]

Please help me find the mistake, because my diagram becomes different from the one in the picture.

Looking at the circuit, I see that:
T1=Co=A*B +A*Cin +B*Cin=Q1*Q1 +Q1*X +Q2*X
T2=S=A XOR B XOR Cin = Q1 XOR Q2 XOR X

and then i get a small table to organize everything:

Code (Text):
present   next
state      state
x=0         x=1
Q0 Q1   T1 T2 Z    | T1 T2 Z
0 0     0  0   0    0   1  0
0 1     0  1   0    1   0  0
1 0     0  1   0    1   0  0
1 1     1  0   0    1   1  1
and obviously if i draw the diagram it looks much different from the one I'm supposed to get.

Can anyone tell me where did I go wrong?

Last edited by a moderator: May 4, 2017
2. Sep 28, 2010

### vela

Staff Emeritus
I agree with you. I think the diagram is wrong.