M74HCT257 查看數據表（PDF） - STMicroelectronics
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M74HCT257 Datasheet PDF : 10 Pages
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M74HCT257
INPUT AND OUTPUT EQUIVALENT CIRCUIT
PIN DESCRIPTION
PIN No
1
2, 5, 14, 11
3, 6, 13, 10
4, 7, 12, 9
15
8
16
SYMBOL
SELECT
1A to 4A
1B to 4B
1Y to 4Y
OE
GND
Vcc
NAME AND FUNCTION
Common Data Select
Input
Data Input From Source A
Data Input From Source B
3 State Multiplexer
Outputs
3 State Output Enable
Inputs (Active Low)
Ground (0V)
Positive Supply Voltage
TRUTH TABLE
OE
H
L
L
L
L
X : Don’t Care
Z : High Impedance
LOGIC DIAGRAM
INPUTS
SELECT
A
X
X
L
L
L
H
H
X
H
X
OUTPUT
B
Y
X
Z
X
L
X
H
L
L
H
H
This logic diagram has not be used to estimate propagation delays
2/10
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