74LCX646 Datasheet, PDF (3/10 Pages) Fairchild Semiconductor – Low Voltage Octal Transceiver/Register with 5V Tolerant Inputs and Outputs

Functional Description
In the transceiver mode, data present at the HIGH imped-
ance port may be stored in either the A or B register or
both. The select (SAB, SBA) controls can multiplex stored
and real-time. The examples shown below demonstrate the
four fundamental bus-management functions that can be
performed.
The direction control (DIR) determines which bus will
receive data when OE is LOW. In the isolation mode (OE
HIGH), A data may be stored in one register and/or B data
may be stored in the other register. When an output func-
tion is disabled, the input function is still enabled and may
be used to store and transmit data. Only one of the two
busses, A or B, may be driven at a time.
Real-Time Transfer
Bus B to Bus A
Real-Time Transfer
Bus A to Bus B
OE DIR CPAB CPBA SAB SBA
LL X
X XL
Transfer Storage
Data to A or B
OE DIR CPAB CPBA SAB SBA
L
H
X
X
L
X
Storage
OE DIR CPAB CPBA SAB SBA
L
L
X H or L X
H
L
H H or L X
H
X
OE
L
L
H
H
DIR
H
L
X
X
CPAB CPBA
X
 X
X
 X
SAB
L
X
X
X
SBA
X
L
X
X
3
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