Combinational Logic Circuits with NAND and NOR Gates

Digital Logic Design Lab. Experiment#2

Experiment #2

Combinational Logic Circuits with NAND and NOR gates

OBJECTIVES

1. Understanding how to construct other combinational logic gates using NOR, or NAND gates.

2. Understanding how to construct any combinational logic function using NAND or NOR gates only.

BACKGROUND

The Boolean expression for the NOR gate is F=(A+B); in deMorgan’s theorem, F=(A+B)=A'B'. The NOR gate can be used to construct NOT; OR; AND; NAND; and XOR gates. We will attempt to construct various logic gates in this experiment by connecting NOR gates in different ways.

The Boolean expression for the NAND gate is F=(AB); in deMorgan’s theorem, F=(AB)=A'+B'. The NAND gate like the NOR gate can be used to construct NOT; OR; AND; NAND; and XOR gates. We will attempt to construct various logic gates in this experiment by connecting NAND gates in different ways.

EQUIPMENTS REQUIRED

KL-31001 trainer kit; 74LS00 (Quad 2 input NAND), 74LS02 (Quad 2 input NOR), 74LS 08 (Quad 2 input AND), 74LS32 (Quad 2 input OR), 74LS 04 (Hexa Not gates).

PRELAB:

1) Carefully read the procedures of your experiment. Draw circuit connection in pin diagram and logic diagram for step (a) in each part, and write down the truth table.

PROCEDURES:

NOR gate

Part I:

a) Use the 74LS02 NOR gates to build an inverter as shown in figure (1).

b) Connect the circuit (according to the pin diagram in your prelab), on the breadboard of the trainer kit, connect input A to data switch SW0, and output F to LED L1, and verify the truth table.

Part II:

a) Use the 74LS02 NOR gates to build an OR gate as shown in figure (2).

b) Connect the circuit (according to the pin diagram in your prelab), on the breadboard of the trainer kit, connect inputs A, B, and output F to SW1, SW0, and L1 respectively, and verify the truth table.

NAND gate

Part III:

a) Use the 74LS00 NAND gates to build an inverter as shown in figure (3).

b) Connect the circuit (according to the pin diagram in your prelab), on the breadboard of the trainer kit, connect input A to data switch SW0, and output F to LED L1, and verify the truth table.

Part IV:

a) Use the 74LS00 NAND gates to build an AND gate as shown in figure (4).

Part V:

a) Use the 74LS00 NAND gates to build an OR gate as shown in figure (5).

Part VI:

c) Use the 74LS00 two input NAND gates to build a 3 input NAND gate as shown in figure (6).

d) Connect the circuit (according to the pin diagram in your prelab), on the breadboard of the trainer kit, connect inputs A, B, C, and output F to SW2, SW1, SW0, and L1 respectively, and verify the truth table.

Note: Don’t forget to connect the Vcc and GND for each IC used throughout your experiment.

Exercise:

v Use your own design to:

a) Build a NAND gate using 2 inputs NOR gates draw logic diagram.

b) Build 3 input NOR using 2 inputs NOR gates draw logic diagram.

c) Build an inverter using XOR gate draw logic diagram.

v Implement the following function with NAND gates only:

F= xy + xy + z

1By: Eng. Ruba A. Salamah