TLF9390

February 1988

MM54HC148MM74HC148

8-3 Line Priority Encoder

General Description

This priority encoder utilizes advanced silicon-gate CMOS

technology It has the high noise immunity and low power

consumption typical of CMOS circuits as well as the speeds

and output drive similar to LB-TTL

This priority encoder accepts 8 input request lines 0 – 7 and

outputs 3 lines A0 – A2 The priority encoding ensures that

only the highest order data line is encoded Cascading cir-

cuitry (enable input EI and enable output EO) has been pro-

vided to allow octal expansion without the need for external

circuitry All data inputs and outputs are active at the low

logic level

All inputs are protected from damage due to static dis-

Features

Y

Typical propagation delay 13 ns

Y

Wide supply voltage range 2V – 6V

Connection Diagram

Dual-In-Line Package

TLF9390 – 1

Order Number MM54HC148 or MM74HC148

Truth Table

Inputs

Outputs

EI

01234567

A2

A1

A0

GS

EO

H

X

XXXXXXX

H

H

H

H

H

L

H

HHHHHHH

H

H

H

H

L

L

X

XXXXXX

L

L

L

L

L

H

L

X

XXXXX

L

H

L

L

H

L

H

L

X

XXXX

LH

H

L

H

L

L

H

LX

X

X

X

L

H

H

H

L

H

H

L

H

LX

X

X

L

H

H

H

H

H

L

L

L

H

L

X

X

L

HHHHH

H

L

H

L

H

L

X

L

HHHHHH

H

H

L

L

H

L

L

HHHHHHH

H

H

H

L

H

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A