Functional Description (Continued)
Inputs
Inputs/Outputs (Note 1)
A0 thru A7 B0 thru B7
Operating Mode
OEAB OEBA
CPAB
CPBA
SAB
X
SBA
X
L
L
H
H
H
H
X
L
H or L
H or L
Input
Input
Isolation
N
N
X
X
Store A and B Data
X
H
L
N
N
H or L
X
X
Input
Not Specified
Output
Input
Store A, Hold B
N
X
X
Input
Store A in Both Registers
Hold A, Store B
H or L
N
N
X
X
Not Specified
Output
Output
L
N
X
X
X
Input
Store B in Both Registers
Real-Time B Data to A Bus
Store B Data to A Bus
Real-Time A Data to B Bus
Stored A Data to B Bus
Stored A Data to B Bus and
Stored B Data to A Bus
L
L
X
X
L
Input
L
L
X
H or L
X
X
H
X
H
H
H
H
H
L
X
L
Input
Output
Output
H or L
H or L
X
H
H
X
H or L
H
Output
=
=
=
H
L
X
HIGH Voltage Level
LOW Voltage Level
Immaterial
=
N
LOW to HIGH Clock Transition
Note 1: The data output functions may be enabled or disabled by various signals at OEAB or OEBA 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.
5
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