Philips Semiconductors

Product specification

74F381

Arithmetic Logic Unit

1

1989 Mar 01

853–0418 95907

FEATURES

look-ahead generator

DESCRIPTION

The 74F381 performs three arithmetic and three logic operations on

two 4-bit words, A and B. Three additional Select (S0–S2) input

codes force the Function outputs Low or High. Carry Propagate (P)

and Generate (G) ouputs are provided for use with the 74F182

Carry Look Ahead Generator for high-speed expansion to longer

word lengths. For ripple expansion, refer to the 74F382 ALU data

sheet.

Signals applied to the Select inputs (S0–S2) determine the mode of

operation, as indicated in the Function Select Table. An extensive

listing of input and output function levels is shown in the Function

Table. The circuit performs the arithmetic functions for either

active-HIgh or active-Low operands, with output levels in the same

convention. In the subtract operating modes, it is necessary to force

a Carry (High for active-HIgh operands, Low for active-Low

operands) into the Cn input of the least significant package. The

Carry Generate (G) and Carry Propagate (P) outputs supply input

signals to the 74F182 Carry look-ahead generator for expansion to

longer word length, as shown in Figure 1. Note that a 74F382 ALU is

used for the most significant package. Typical delays for Figure 1

are given in Table 1.

PIN CONFIGURATION

20

19

18

17

16

15

14

7

6

5

4

3

2

1

13

8

VCC

A1

B1

A0

B0

S0

S1

S2

F0

F1

GND

A2

B2

A3

B3

Cn

P

G

F3

F2

SF00921

12

9

11

10

TYPE

TYPICAL

PROPAGATION

DELAY

TYPICAL SUPPLY

CURRENT (TOTAL)

74F381

6.5ns

59mA

ORDERING INFORMATION

DESCRIPTION

COMMERCIAL RANGE

20-pin plastic DIP

N74F381N

20-pin plastic SO

N74F381D

INPUT AND OUTPUT LOADING AND FAN OUT TABLE

PINS

DESCRIPTION

74F (U.L.)

HIGH/LOW

LOAD VALUE

HIGH/LOW

A0 – A3

A operand inputs

1.0/4.0

20

µA/2.4mA

B0 – B3

A operand inputs

1.0/4.0

20

µA/2.4mA

S0 – S2

Function select inputs

1.0/1.0

20

µA/0.6mA

Cn

Carry input

1.0/4.0

20

µA/2.4mA

P

Carry Propagate ouptut (active-Low)

50/33

1.0mA/20mA

G

Carry Generate ouptut (active-Low)

50/33

1.0mA/20mA

F0–F3

Outputs

50/33

1.0mA/20mA

NOTE:

One (1.0) FAST unit load is defined as 20

µA in the High state and 0.6mA in the Low state.