Lab- J-K FF
Objectives
The following are objectives of this lab:
Use various conditions to test the characteristics of the J-K flip-flop. Included in the procedures are various asynchronous and synchronous input modes.
Materials Needed
1. 74LS76 dual J-K flip-flop
2. LEDs: (1) red, (1) green, (1) yellow
3. Resistors: (3) 330?, (4) 1.0 k?
4. One 4-position DIP switch
5. Function Generator / Oscilloscope / Leads / KeySight BenchVue software
Background
The J-K flip-flop is a clocked S-R flip-flop with additional circuitry to replace the invalid state of S = 1, R = 1. The new mode when J = 1 and K = 1 is called toggle. The toggle state causes the flip- flop to change state to the opposite state if both S and R equal 1. Tables 1 a, b, and c below give the states for each type of flip flop for all states of input.
S-R FF
Inputs S R
|
Output Q
|
0
|
0
|
Latched
|
0
|
1
|
0
|
1
|
0
|
1
|
1
|
1
|
Invalid
|
Table 1a
D-Latch
Input D
|
Output Q
|
No equivalent
|
0
|
0
|
1
|
1
|
No equivalent
|
Table 1b
J-K FF
Inputs J K
|
Output Q
|
0
|
0
|
Latched
|
0
|
1
|
0
|
1
|
0
|
1
|
1
|
1
|
Toggle
|
Table 7-1c
The J-K FF will be used in this lab to demonstrate its unique capabilities.
Procedure
1. Turn on computer and locate KeySight BenchVue software.
Turn on the Oscilloscope (reads outputs) / Function Generator (clock input). (You may need T.A. or instructor assistance)
Construct the circuit of Figure 1 below.
Set (PRE)‾ and (CLR)‾ to a logic 1.
Connect the TTL signal from the function generator and set frequency to 1 Hz.
Using the BenchVue software, save a screenshot of the input (Channel 1) and output, Q, (Channel 2) for all combinations of J and K. Label all screenshots appropriately.
![2369_Circuit Diagram.png](https://secure.tutorsglobe.com/CMSImages/2369_Circuit%20Diagram.png)
2. Construct the circuit of Figure 2.
Using the BenchVue software save screenshots of the input (Channel 1) and output, Q‾, (Channel 2) for all combinations of J and K. Label all screenshots appropriately.
![1437_Circuit Diagram1.png](https://secure.tutorsglobe.com/CMSImages/1437_Circuit Diagram1.png)
3. Construct the circuit of Figure 3.
Using the BenchVue software save screenshots of the outputs, Q1and Q2 on the same screen (Channels 1 and 2) for all combinations of J and K. Then repeat this for outputs, Q1‾ and Q2‾ for all combinations of J and K. Label all screenshots appropriately.
![41_Circuit Diagram2.png](https://secure.tutorsglobe.com/CMSImages/41_Circuit Diagram2.png)
HD74LS76A
![286_Block Diagram and PIN Arrangement.png](https://secure.tutorsglobe.com/CMSImages/286_Block%20Diagram%20and%20PIN%20Arrangement.png)
REQUIRED SUBMITTAL: You will NOT turn in this handout!!!
You will do a formal lab report including the following sections:
OBJECTIVE (Sentence format. Be thorough!)
DATA -Use Multisim to create the circuits constructed in Figure 1, 72 and 3. Give each circuit a meaningful name that explains their function. Include labeled screenshots taken in the course of the lab (these should have labels similar to the circuit labels).
DISCUSSION - (Sentence / Paragraph format) Discuss the operation and/or function performed by each of the (3) flip-flop circuits by analysis of the outputs.