TLF6420

May 1989

54LS279DM54LS279DM74LS279

Quad S-R Latches

General Description

The ’LS279 consists of four individual and independent Set-

Reset Latches with active low inputs Two of the four latch-

es have an additonal S input ANDed with the primary S

input A low on any S input while the R input is high will be

stored in the latch and appear on the corresponding Q out-

put as a high A low on the R input while the S input is high

will clear the Q output to a low Simultaneous transistion of

the R and S inputs from low to high will cause the Q output

to be indeterminate Both inputs are voltage level triggered

and are not affected by transition time of the input data

Features

Y

Alternate militaryaerospace device (54LS279) is avail-

able Contact a National Semiconductor Sales Office

Distributor for specifications

Connection Diagram

Dual-In-Line Package

TLF6420 – 1

Order Number 54LS279DMQB 54LS279FMQB 54LS279LMQB

DM54LS279J DM74LS279M or DM74LS279N

See NS Package Number E20A J16A M16A N16E or W16A

Function Table

Inputs

Output

S(1)

R

Q

LL

H

LH

H

HL

L

HH

This output level is pseudo stable that is it may not persist when the S and R

inputs return to their inactive (high) level

Note 1

For latches with double S inputs

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A