Digital Design: IMPLEMENTATION OF COMBINATIONAL LOGIC BY STANDARD ICs and PROGRAMMABLE ROM MEMORIES

Chapter 12

IMPLEMENTATION OF COMBINATIONAL LOGIC BY

STANDARD ICs and PROGRAMMABLE ROM

MEMORIES

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 2

Lesson 1

STANDARD ICs FOR DESIGN IMPLEMENTATION

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 3

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC• Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 4

Standard ICs for a combinational circuit• Binary arithmetic circuits, • Decoders, • Encoders, • Multiplexers, • Code converters, • Digital comparator for magnitude and equality,• Parity generators and checkers • Bit wise ‘AND’, ‘OR’, ‘NOT’ logic processing

circuits.

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 5

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 6

IC for addition /subtraction

• CMOS based 74HC 83 and TTL 7483 family other ICs —four bits full adders

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 7

Full Adder/Subtractor• 7483 4-bit Full Adder

74834-bit

Full Adder

Vcc

B0-B3

A0-A3

S0-S3

CyCy-1

GND

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 8

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC• Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 9

IC for Decoder• MSI chip 74138 is 3-line to 8-line (1 of 8)

decoder IC with three control pins G0, G1, and G2. G0, and G1 control pins are activated by '0' and G2 pin is activated by '1'.

• Output logic active state 0• Inactive output state tristate

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 10

Decoder• 74138— 3 to 8 decoder with active output 0 and

tristate remaining pins

74384-bit

Full Adder

Vcc

G0

A0-A2 -A3 Y0-Y7

G2

GND

G1

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 11

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC• Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 12

IC for encoder

• CMOS based 74HC148 and TTL 74148 family other ICs —8:3 encoder with one active ‘0’ gate enable pin and one active ‘0’ out enable pin

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 13

8:3 Encoder• 74148

741484-bit

Encoder

Vcc

I0-I7F0-F2

OEG

GND

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 14

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC• Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 15

IC for Multiplexer

• CMOS based 74HC 156 and TTL 74156 family other ICs —4 to 1 multiplexer

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 16

Multiplexer• 74156 MUX Vcc

I0-I3 F

A1GND

Strobe

A0

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 17

Outline

• Design by standard ICs• Adder/Subtractor IC• Decoder IC• Encoder IC • Multiplexer IC • Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 18

IC for Magnitude Comparator

• 7485 4-bit Digital Magnitude Comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 19

Full Adder/Subtractor• 7485 Digital Comparator

7485Digital

MagnitudeComparator

Vcc

B0-B3

A0-A3A>B

GND

A>BA=B

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 20

Summary

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 21

We learnt ICs for • Full adder/subtractor• Decoder• Encoder• Multiplexer• Magnitude comparator

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 22

End of Lesson 1

STANDARD ICs FOR DESIGN IMPLEMENTATION

Ch12L1-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 23

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