1. Counter
Section 6.3

2. Types of Counter
Binary Ripple Counter
Synchronous Counter

3. Binary Ripple Counter
Respond to negative
edge of the clock
Reset

4. Binary Ripple Counter
D0(n+1)=A0(n)’
The first flip-flop always
toggles itself. 1 1 A3 A2 A1 A0 2 1
Each D flip-flop is designed to flip
Itself. 3 1 4 1
Each D flip-flop is triggered
by the output of the previous DFF.
Reset

5. 0→1
Binary Ripple Counter 1
1 →0 A3 A2 A1 A0 1
0 →0 2 1
1→1
0 →0 3
1 →1
0 →0 4
1 →1
Reset

6. 0→1 → 0
Binary Ripple Counter 1
1 →0 → 1 A3 A2 A1 A0 1
0 →0 →1 2 1
1→1 →0
0 →0 →0 3
1 →1 →1
0 →0 →0 4
1 →1 →1
Reset

7. Binary Ripple Counter 1
Each DFF is triggered
by the previous DFF. 2 3
Respond to negative
edge of the clock 4
Reset

8. Sequence A3 A2 A1 A0 1
Start from 0, advance to
15, go back to 0.

9. Count Down D A3 A2 A1 A0 15 1 14 13 12 11 10 9 8 7
It is the rising edge that
triggers the flip-flop.
So remove the bubble.
Make the DFF positive edge
triggered.

10. Synchronous Counters
Synchronous counters are different from ripple counters in that clock pulses are applied to the input of all flip-flops.

11. Binary Counter 1 1 2 3 4

12. JK Flip-Flop

13. Binary Counter 1
0→1 1
0→1
0 →0 2
0 →0
0 →0 3
0 →0
0 →0 4

14. 1
0→1 →0 1
0→1 → 0
0 →0 →1 2
0 →0 →0
0 →0 →0 3
0 →0 →0
0 →0 →0 4