This document discusses T flip-flops and JK flip-flops in the context of a digital logic class at Iowa State University. T flip-flops toggle their state based on their input, while JK flip-flops can function as both SR and T flip-flops depending on their inputs. The document includes circuit diagrams, truth tables, and a brief explanation of how each flip-flop operates.

1. Instructor: Alexander Stoytchev
http://www.ece.iastate.edu/~alexs/classes/
CprE 281:
Digital Logic

2. T Flip-Flops
&
JK Flip-Flops
CprE 281: Digital Logic
Iowa State University, Ames, IA
Copyright © Alexander Stoytchev

3. Administrative Stuff
• HW 8 is out
• It is due next Monday (Oct 27)

4. T Flip-Flop

5. Motivation
A slight modification of the D flip-flop that can be used
for some nice applications.
In this case, T stands for Toggle.

6. [ Figure 5.15a from the textbook ]
T Flip-Flop

7. [ Figure 5.15a from the textbook ]
T Flip-Flop
Positive-edge-triggered
D Flip-Flop

8. [ Figure 5.15a from the textbook ]
T Flip-Flop
What is this?

9. What is this?
Q
Q
T
D

10. Q
Q
T
D
What is this?
+ = ?

11. T
0
1
D Q
Q
Clock
T Flip-Flop

12. What is this?
Q
T
D

13. What is this?
Q
T
D
D = QT + QT

14. What is this?
Q
T
D
D = Q + T

15. What is this?
D = Q + T
D
Q
T

16. What is this?
+ = ?

17. T
D Q
Q
Clock
T Flip-Flop

18. T Flip-Flop
(How it Works)
If T=0 then it stays in its current state
If T=1 then it reverses its current state
In other words the circuit “toggles” its state
when T=1. This is why it is called T flip-flop.

19. [ Figure 5.15a,b from the textbook ]
T Flip-Flop
(circuit and truth table)

20. [ Figure 5.15a,c from the textbook ]
T Flip-Flop
(circuit and graphical symbol)

21. [ Figure 5.15d from the textbook ]
T Flip-Flop (Timing Diagram)

22. JK Flip-Flop

23. [ Figure 5.16a from the textbook ]
JK Flip-Flop
D = JQ + KQ

24. [ Figure 5.16 from the textbook ]
JK Flip-Flop
J Q
Q
K
0
1
Q t 1
+
 
Q t
 
0
(b) Truth table (c) Graphical symbol
J
0
0
0 1
1
1 Q t
 
1
K
D Q
Q
Q
Q
J
Clock
(a) Circuit
K

25. JK Flip-Flop
(How it Works)
A versatile circuit that can be used both as a SR
flip-flop and as a T flip flop
If J=0 and S =0 it stays in the same state
Just like SR It can be set and reset
J=S and K=R
If J=K=1 then it behaves as a T flip-flop

26. Questions?

27. THE END