MC74ACT157 데이터 시트보기 (PDF) - ON Semiconductor

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MC74ACT157

Quad 2-Input Multiplexer

ON Semiconductor 

MC74AC157, MC74ACT157

E I0a I1a I0b I1b I0c I1c I0d I1d

S

Za

Zb

Zc

Zd

Figure 2. Logic Symbol

FUNCTIONAL DESCRIPTION

The MC74AC157/74ACT157 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

MC74AC157/74ACT157 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 MC74AC157/74ACT157 is the

moving of data from two groups of registers 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

MC74AC157/74ACT157 can generate any four of the

sixteen different functions of two variables with one

variable common. This is useful for implementing gating

functions.

I0a

I1a

I0b

I1b

I0c

I1c

I0d

I1d

E

S

Za

Zb

Zc

Zd

NOTE: This diagram is provided only for the understanding of logic

operations and should not be used to estimate propagation delays.

Figure 3. Logic Diagram

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