Arithmetic Logic
Description
Philips Semiconductors
Product specification
Arithmetic Logic Unit
74F381
FEATURES
• Low-input loading minimizes drive requirements • Performs six arithmetic and logic functions • Selectable Low (clear) and High (preset) functions • Carry Generate and Propagate outputs for use with Carry
look-ahead generator
PIN CONFIGURATION
A1 1 B1 2 A0 3 B0 4 S0 5 20 V CC 19 A2 18 B2 17 A3 16 B3 15 Cn 14 P 13 G 12 F3 11 F2
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.
S1 6 S2 7 F0 8
F1 9 GND 10
SF00921
TYPE 74F381
TYPICAL PROPAGATION DELAY 6.
5ns
TYPICAL SUPPLY CURRENT (TOTAL) 59mA
ORDERING INFORMATION
DESCRIPTION 20-pin plastic DIP 20-pin plastic SO COMMERCIAL RANGE VCC = 5V ±10%, Tamb = 0°C to +70°C N74F381N N74F381D
INPUT AND OUTPUT LOADING AND FAN OUT TABLE
PINS A0 – A3 B0 – B3 S0 – S2 Cn P G A operand inputs A...
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