sorry for my comment above i have not considered positive edge triggered clock.THe correct solution will be this->as positive edge triggered clock is applied we have following conditions->
-> Q1 will change every time
-> Q2 will change only when Q1 changes from 0 to 1.
->Q3 changes only when Q2 changes from 0to 1.
so we will get this table..
clock |
Q3 |
Q2 |
Q1 |
t3 |
t2 |
t1 |
clr |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
2 |
1 |
1 |
0 |
1 |
1 |
1 |
0(clr is active) |
3 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
so it is a down counter and only 3 states are possible.