Lab #8: D Flip-Flops SAIT- ENT-DIGI-210
Lab #8: D Flip-Flops
Updated August 28, 2014
Lab Description:
Construct and analyze basic D Flip-Flop circuits.
Outline Objectives:
Learning outcome 9: Analyze the operating characteristics of latches and flip-flops.
Pre-Lab Preparation:
Read notes on the design and operation of:
D-Flop-Flops
Asynchronous inputs
Equipment Required:
Parts kit and Vulcan Board
7474 – D Flip-Flop
Evaluation:
Complete the design, showing all work.
Build and analyze a circuit.
Answer the questions.
Additional Notes:
Procedure 1:
Demonstrate the operation of a D Flip-Flop including the asynchronous inputs.
1. Use EWB to design, built and demonstrate the function of a D Flip-Flop, including its asynchronous inputs.
2. Wire the circuit on your breadboard. Use the LEDs on the Vulcan board to demonstrate the state of the four inputs and the two outputs.
3. Verify its operation by completing the function table below. Select appropriate inputs and outputs to demonstrate its full range of function (you may add or remove rows from the table as appropriate).
4. Demonstrate its operation to the instructor.
Inputs / OutputsCLK / D / PRE / CLR / Q / Q’ / Mode
Answer the following questions:
1. Which inputs of this D Flip-Flop are active low? What happens to the D and Clock inputs when either the preset or clear are active?
2. What happens if both the preset and clear are active? Paraphrase what is stated by chip manufacturer Texas Instruments on active preset and clear inputs for the 74LS74 D Flip-Flop (go to www.ti.com). (you must look at the specification sheet from Texas Instruments to answer this question)
Signature Procedure 1: ______
Procedure 2:
Create a 2-bit storage device using D Flip-Flops
1. Use circuit simulation software to design a 2-bit storage device using two D-Flip-Flops. There should be an input switch for each D, and the clock input should be shared. There should also be a master reset for the 2-bit storage device. Hints: Each D Flip-Flop stores 1 bit. Do not leave unused input floating.
2. Wire the circuit on your breadboard. Use LEDs on the inputs and on the outputs.
3. Operate each switch and observe the operation of the flip-flops. Demonstrate and explain the circuit’s function to the lab instructor. Points of interest include:
a. Sequence of events to store a 2-bit value
b. How to clear the flip-flops
c. Status of unused inputs
Answer the following question:
If storing digits on the 2-bit storage device created in part 2, is it necessary to use the master reset before storing a new value? Explain.
Signature Procedure 2: ______
Student Name: ______Date: ______
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