HD74AC157 查看數據表（PDF） - Hitachi -> Renesas Electronics

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HD74AC157

Quad 2-Input Multiplexer

Hitachi -> Renesas Electronics 

HD74AC157

Logic Symbol

E I0a I1a I0b I1b I0c I1c Iod I1d

S

Za

Zb

Zc

Zd

Pin Names

I0a to I0d

I1a to I1d

E

S

Za to Zd

Source 0 Data Inputs

Source 1 Data Inputs

Enable Input

Select Input

Outputs

Functional Description

The HD74AC157 is a quad 2-input multiplexer. It selects four bits of data from two sources under the

control of a common Select input (S). The Enable input (E) is active-Low. when E is High, all of the

outputs (Z) are forced Low regardless of all other inputs. The HD74AC157 is the logic implementation of

a 4-pole, 2-position switch where the position of the switch is determined by the logic levels supplied to the

Select input. The logic equations for the outputs are shown below:

Za = E•(I1a•S + I0a•S)

Zb = E•(I1b•S + I0b•S)

Zc = E•(I1c•S + I0c•S)

Zd = E•(I1d•S + I0d•S)

A common use of the HD74AC157 is the moving of data from two groups of register to four common

output busses. The particular register from which the data comes is determined by the state of the Select

input. A less obvious use is as a function generator. The HD74AC157 can generate any four of the sixteen

different functions of two variables with one variable common. This is useful for implementing gating

functions.

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