Experiment- 3

Aim :-

Designing half and full adder, half and full subtractor using logic gates.

Apparatus :-

Software: Orcad Capture

Hardware: Digital IC Trainer Kit

IC used- 7400 , 7402 , 7404 , 7408. 7432 ,7486 and patch cords.

Procedure :-

Software Implementation

1. Open Capture CIS application.

2. Go to File->New->Project.

3. Give a project name and specify the directory to save the project. Click OK.

4. Select “Create a blank Project” and click OK.

5. Go to Place->Part->Add Library. Select “7400” library and choose the required gate and place it

on the grid.

6. Go to Place->Wire and connect the wires as required.

7. Click Place->Part->Add Library- Select “Source”Library and choose “Digiclock” option.

8. Set the ONTIME and OFFTIME of the digiclock as required.

9. Place the Digiclock at the required inputs.

10. Go to Pspice->Create netlist.

11. Again click Pspice->New Simulation Profile and give a suitable name.

12. Set “Run to time” in the Simulation Settings and click OK.

13. Click Pspice->Marker->Voltage/Level Marker and place it at the desired inputs and outputs.

14. Go to Pspice->Run and the output shall appears.

Hardware Implementation

1. Implement the circuits as per the circuit diagram using patch cords.

2. Switch on the board and enable input keys(LED indicators).

3. Observe and record the logic outputs using logic output LED indicators.

4. Verify the truth table.

Precautions:-

1.Circuit should be properly connected.

2. Switch off the board if not In use.

3. Wires should be held by their heads while being removed else they may get damaged.

Circuit Diagram: Half Adder

Output:

Truth Table:

A B Sum (U1) Carry (U2)

0 0 0 0

0 1 1 0

1 0 1 0

1 1 0 1

Circuit Diagram: Full Adder

Output:

Truth Table:

A B C Sum (U1) Carry (U2)

0 0 0 0 0

0 0 1 1 0

0 1 0 1 0

0 1 1 0 1

1 0 0 1 0

1 0 1 0 1

1 1 0 0 1

1 1 1 1 1

Circuit Diagram: Half Subtractor

Output:

Truth Table:

A B Difference

(U7)

Borrow

(U6)

0 0 0 0

0 1 1 1

1 0 1 0

1 1 0 0

Circuit Diagram: Full Subtractor

Output:

Truth Table:

A B C Difference

(U9)

Borrow

(U12)

0 0 0 0 0

0 0 1 1 1

0 1 0 1 1

0 1 1 0 1

1 0 0 1 0

1 0 1 0 1

1 1 0 0 0

1 1 1 1 1