dm74as651 Fairchild Semiconductor, dm74as651 Datasheet - Page 2

• Manufacturer Part Number: dm74as651
• Description: Octal Bus Transceiver And Register
• Manufacturer: Fairchild Semiconductor

www.fairchildsemi.com
GAB GBA CAB
Connection Diagram
Function Table
H
L
X
Note 1: The data output functions may be enabled or disabled by various signals at the GAB and GBA inputs. Data input functions are always enabled,
i.e., data at the bus pins will be stored on every LOW-to-HIGH transition on the clock inputs.
Note 2: If the select control is LOW, the clocks can occur simultaneously. If the select control is HIGH, the clocks must be staggered in order to load both
registers.
H
H
H
H
L
L
L
L
X
L
L
LOW Level
LOW-to-HIGH Transition
HIGH Level
Irrelevant
H
H
H
H
H
H
L
L
L
X
L
H or L H or L
H or L
H or L H or L
H or L
X
X
X
INPUTS
H or L
H or L
CBA
X
X
X
(Note
SAB
2)
H
H
X
X
X
X
L
X
X
X
X
(Note
SBA
2)
H
H
X
X
L
X
X
X
X
X
X
Unspecified
(Note 1)
Output
Output
Output
THRU
DATA I/O (Note 1)
Input
Input
Input
Input
A1
A8
Unspecified
(Note 1)
Output
Output
Output
THRU
2
Input
Input
Input
Input
B1
B8
Isolation
Store A and B Data
Real Time B Data to A
Bus
Stored B Data to A Bus
Real Time A Data to B
Bus
Stored A Data to B Bus
Stored A Data to B Bus
& Stored B Data to A Bus & Stored B Data to A Bus
Store A, Hold B
Store A in both registers
Hold A, Store B
Store B in both registers
DM74AS651
OPERATION OR FUNCTION
Isolation
Store A and B Data
Real Time B Data to A
Bus
Stored B Data to A Bus
Real Time A Data to B
Bus
Stored A Data to B Bus
Stored A Data to B Bus
Store A, Hold B
Store A in both registers
Hold A, Store B
Store B in both registers
DM74AS652