Post on 26-Dec-2015
Flip-Flops
RS Flip-flop
S
R
OutputsInputs
X
X
RS Flip-flop - definition
Inputs Output
S R
0 0 Unchanged
1 0
0 1
1 1 Not allowed
01 XX
10 XX
RS Flip-flop waveforms
01 XX 01 XX
Types of flip-flops:a) dynamicb) synchronized
Example
Example continuation
RS flip-flop formed by cross-coupling NOR gates
RS flip-flop formed by cross-coupling NAND gates
Transfer circuit
RS latch
D latch
Shift register
The progression of states by the counter
X3 X2 X1
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
0 0 0
… … …
Example: Binary counter
Example: Gated-clock binary counter
JK flip-flop
Example: Binary counter
made with JK flip-flops
Example: Up-down counter
Integrated circuits
Counter design:Design rule for RS flip-flops
The present state
The next state S R
0 0 0 d
1 1 d 0
0 1 1 0
1 0 0 1
Counter design: Exercise (RS version)
Design a counter using three RS Flip-Flops
to sequence as follows
A B C
0 0 0
1 1 1
1 0 1
1 1 0
0 0 1
0 1 0
0 0 0
1 1 1
1 0 1
... ... ...
Solution: (RS version)
Solution: Counter with RS flip-flops
AS
R
BS
R
S
R
C
Counter design: Design rule for JK flip-flops
The present state
The next state J K
0 0 0 d
1 1 d 0
0 1 1 d
1 0 d 1
Counter design: Exercise (JK version)
Design a counter using three JK Flip-Flopsto sequence as follows
A B C
0 0 0
1 1 1
1 0 1
1 1 0
0 0 1
0 1 0
0 0 0
1 1 1
1 0 1
... ... ...
Solution: (JK version)Counter with JK flip-flops