74ACQ657SPC Ver la hoja de datos (PDF) - Fairchild Semiconductor
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74ACQ657SPC
Fairchild Semiconductor
74ACQ657SPC Datasheet PDF : 10 Pages
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Functional Description
The Transmit/Receive (T/R) input determines the direction
of the data flow through the bidirectional transceivers.
Transmit (active HIGH) enables data from the A-Port to the
B-Port; Receive (active LOW) enables data from the B-Port
to the A-Port.
The Output Enable (OE) input disables the parity and
ERROR outputs and both the A and B Ports by placing
them in a HIGH-Z condition when the Output Enable input
is HIGH.
When transmitting (T/R HIGH), the parity generator detects
whether an even or odd number of bits on the A-Port are
HIGH and compares these with the condition of the parity
select (ODD/EVEN). If the Parity Select is HIGH and an
even number of A inputs are HIGH, the Parity output is
HIGH.
In receiving mode (T/R LOW), the parity select and number
of HIGH inputs on port B are compared to the condition of
the Parity input. If an even number of bits on the B-Port are
HIGH, the parity select is HIGH, and the PARITY input is
HIGH, then ERROR will be HIGH to indicate no error. If an
odd number of bits on the B-Port are HIGH, the parity
select is HIGH, and the PARITY input is HIGH, the ERROR
will be LOW indicating an error.
Function Table
Number of
Inputs That
Are High
OE
0, 2, 4, 6, 8
L
L
L
L
L
L
1, 3, 5, 7
L
L
L
L
L
L
Immaterial
H
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
Inputs
T/R
H
H
L
L
L
L
H
H
L
L
L
L
X
ODD/EVEN
H
L
H
H
L
L
H
L
H
H
L
L
X
Input/
Output
Parity
H
L
H
L
H
L
L
H
H
L
H
L
Z
Outputs
ERROR
Z
Z
H
L
L
H
Z
Z
L
H
H
L
Z
Outputs Mode
Transmit
Transmit
Receive
Receive
Receive
Receive
Transmit
Transmit
Receive
Receive
Receive
Receive
Z
Function Table
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Inputs
OE
T/R
L
L
L
H
H
X
Outputs
Bus B Data to Bus A
Bus A Data to Bus B
High-Z State
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