### Counter - Jack Ou

```Counter
Section 6.3
Types of Counter
• Binary Ripple Counter
• Synchronous Counter
Binary Ripple Counter
Respond to negative
edge of the clock
Reset
0
Binary Ripple Counter
1
A3
A2
A1
A0
0
0
0
0
1
1. D0(n+1)=A0(n)’
The first flip-flop always
toggles itself.
0
2
1 Each D flip-flop is designed to f
Itself.
0
3
1
0
4
Reset
1
Each D flip-flop is triggered
0→1
Binary Ripple Counter
1
A3
A2
A1
A0
0
0
0
0
0
0
0
1
1 →0
0 →0
2
1 1→1
0 →0
3
1 →1
0 →0
4
Reset
1 →1
0→1 → 0
Binary Ripple Counter
1
A3
A2
A1
A0
0
0
0
0
0
0
0
1
0
0
1
0
1 →0 → 1
0 →0 →1
2
1 1→1 →0
0 →0 →0
3
1 →1 →1
0 →0 →0
4
Reset
1 →1 →1
Binary Ripple Counter
1
Each DFF is triggered
by the previous DFF.
2
3
Respond to negative
edge of the clock
4
Reset
Sequence
A3
A2
A1
A0
0
0
0
0
0
0
0
1
0
0
1
0
1
1
1
1
1
1
1
0
1
1
0
1
0
0
0
0
15, go back to 0.
Count Down
D
A3 A2 A1 A0
15
1
1
1
1
14
1
1
1
0
13
1
1
0
1
12
1
1
0
0
11
1
0
1
1
10
1
0
1
0
9
1
0
0
1
8
1
0
0
0
7
0
1
1
1
It is the rising edge that
triggers the flip-flop.
So remove the bubble.
Make the DFF positive edge
triggered.
Synchronous Counters
• Synchronous counters are different
from ripple counters in that clock
pulses are applied to the input of all
flip-flops.
1
1
Binary Counter
0
0
0
2
0
0
3
0
0
4
JK Flip-Flop
1
1
0→1
Binary Counter
0 →0
0→1
2
0 →0
0 →0
3
0 →0
0 →0
4
1
1
0→1 →0
0 →0 →1
0→1 → 0
2
0 →0 →0
0 →0 →0
3
0 →0 →0
0 →0 →0
4
```