HD74LS248

Rev.3.00, Jul.15.2005, page 2 of 6

Function Table

Inputs

Outputs

Decimal

or

Function

LT

RBI

D

C

B

A

BI/

RBO

a

b

c

d

e

f

g

Note

0

H

H

L

L

L

L

H

H

H

H

H

H

H

L

1

H

X

L

L

L

H

H

L

H

H

L

L

L

L

2

H

X

L

L

H

L

H

H

H

L

H

H

L

H

3

H

X

L

L

H

H

H

H

H

H

H

L

L

H

4

H

X

L

H

L

L

H

L

H

H

L

L

H

H

5

H

X

L

H

L

H

H

H

L

H

H

L

H

H

6

H

X

L

H

H

L

H

H

L

H

H

H

H

H

7

H

X

L

H

H

H

H

H

H

H

L

L

L

L

8

H

X

H

L

L

L

H

H

H

H

H

H

H

H

9

H

X

H

L

L

H

H

H

H

H

H

L

H

H

10

H

X

H

L

H

L

H

L

L

L

H

H

L

H

11

H

X

H

L

H

H

H

L

L

H

H

L

L

H

12

H

X

H

H

L

L

H

L

H

L

L

L

H

H

13

H

X

H

H

L

H

H

H

L

L

H

L

H

H

14

H

X

H

H

H

L

H

L

L

L

H

H

H

H

15

H

X

H

H

H

H

H

L

L

L

L

L

L

L

1

BI

X

X

X

X

X

X

L

L

L

L

L

L

L

L

2

RBI

H

L

L

L

L

L

L

L

L

L

L

L

L

L

3

LT

L

X

X

X

X

X

H

H

H

H

H

H

H

H

4

H; high level, L; low level, X; irrelevant

Notes: 1. The blanking input (BI) must be open or held at a high logic level when output functions 0 through 15 are

desired. The ripple-blanking input (RBI) must be open or high if blanking of a decimal zero is not desired.

2.

When a low logic level is applied directly to the blanking input (BI), all segment outputs are off regardless of

the level of any other input.

3.

When ripple-blanking input (RBI) and inputs A, B, C, and D are a low level with the lamp test input high, all

segment outputs go off and the ripple-blanking output (RBO) goes to a low level (response condition).

4.

When a blanking input ripple blanking input (BI/RBO) is open or held high and a low is applied to the lamp-

test input, all segment outputs are on.