Lab #8: Shift Registers

Lab #8: Shift Registers SAIT- ENT-DIGI-260

Lab #8: Shift Registers

Updated January 2005

Objectives:

1. Observe and analyze the operation of a Universal Shift Register.

2. Use a Universal Shift register in circuit design.

Pre-Lab Preparation:

1. Attend lectures and review the theory of operation of Shift Register circuits.

2. Read the textbook chapters, on-line materials and specification sheets that relate to Universal Shift Register circuits.

3. Design the SIPO Shift Register using EWB, and wire up the lab in advance.

Equipment Required:

1. Experimenter’s board with 5V power supply

2. Function Generator

3. Oscilloscope

4. PC with EWB

5. 74LS194 or 40194 U.S.R., parts kit.

Additional Notes:

Procedure 1:

Observe the operation of a 4-bit Universal Shift Register

1. Identify the 4-bit bi-directional universal shift register that you have within your parts kit and available in EWB. Typically this is a 40194 or a 74194. Use a manual debounced push button Clk for procedure 1 only.

2. Connect a 4-bit bi-directional universal shift register with D3 to D0 hard-wired as 10002 use parallel load, then shift right Q outputs →1000 – 0100 – 0010 – 0001- 00002.

D3 to D0 00012 use parallel load, then shift left Q outputs → 0001 – 0010 – 0100 – 1000 – 00002 .

Note: You may or may not have an exact match for the part in EWB.

3. Design and construct the bi-directional shift register using EWB. Use switches for all other functions. Demonstrate all operating modes to the instructor, including:

(i) Shift Left

(ii) Shift Right

(iii) Load

(iv) Clear

Procedure 2:

Observe the operation of a self-starting 4-bit Shift Register

1. Modify the circuit of procedure 1 or 2 so that it functions as a self-starting ring counter. Include a control circuit so that the first clock pulse automatically initializes the ring counter after power is applied. (Subsequent clock pulses will then only sequence the counter.) Demonstrate the operation to the instructor by powering up the circuit. Note: This circuit may not function in EWB.

Hints for initializing circuits: RC circuit (provide a load or logic high input), or logic-based circuit (“if the output is 0000, perform a function”).

Use the Vulcan trainer Clk output to a Schmitt trigger input, Schmitt trigger output to Clk input of shift register. Count sequence below occurs on power up. Power down the circuit for 20 seconds then power up the count sequence below still occurs.

0001 0010 0100 1000 0001 0010 0100 10002 …… note no, 00002 outputs.

2. Sketch the initializing circuit at the end of the lab.

3. Continue with the next procedure

Procedure 3:

Add a modification to the operation of a self-starting 4-bit Shift Register

Modify the self-starting Shift Register with one of the following choices:

1. Reverses its sequence: 1000, 0100, 0010, 0001, 0010, 0100,1000…

2. Reverses its sequence: 1000, 1100, 1110, 1111, 1110, 1100, 1000…

3. Sequence of a signal light: 0000, 1000, 1100, 1110, 1111, 0000…

4. Connect 2 registers together and create a single high bit that goes from one end to another.

Challenge:

5. Sequence of a light: 0010, 0100, 0001, 1000, 0010…

Answer the following questions.

1. Explain why the shift register from procedure 1 can be both a SISO and a PIPO.

2. Sketch a block diagram of the initializing circuit from procedure 2

3. Explain how to connect two universal shift registers from procedure 1 to create an 8-bit register. Sketch a block diagram.

Signatures:

Procedure 1 simulation, circuit and question: ______

Procedure 2 simulation, circuit and question: ______

Procedure 3 circuit, diagram and question: ______

Student Name: ______Date: ______