74lvth646 Fairchild Semiconductor, 74lvth646 Datasheet - Page 3

• Manufacturer Part Number: 74lvth646
• Description: Low Voltage Octal Transceiver/register With 3-state Outputs
• Manufacturer: Fairchild Semiconductor

Functional Description
In the transceiver mode, data present at the HIGH impedance 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 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 function 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.
OE
OE
L
L
L
DIR
DIR
Real-Time Transfer
H
L
L
Transfer Storage
Bus B to Bus A
Data to A or B
H or L
CPAB CPBA SAB SBA
CPAB CPBA SAB SBA
X
X
H or L
X
X
X
X
H
H
X
L
3
OE
OE
H
H
L
L
L
DIR
DIR
H
Real-Time Transfer
H
X
X
L
Bus B to Bus A
CPAB CPBA SAB SBA
Storage
CPAB CPBA SAB SBA
X


X
X
X


X
X
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L
X
X
X
L
X
X
X
X
L