Functional Description
Inputs
OEAB
L
L
X
H
L
L
L
L
H
H
H
OEBA
H
H
H
H
X
L
L
L
H
H
L
CPAB
H or L
N
N
N
H or L
N
X
X
X
H or L
H or L
CPBA
H or L
N
H or L
N
N
N
X
H or L
X
X
H or L
(Continued)
Inputs/Outputs
(Note 1)
SAB
X
X
X
X
X
X
X
X
L
H
H
SBA
X
X
X
X
X
X
L
H
X
X
H
Output
Output
Input
Output
Input
Input
Not Specified
Output
Output
Not Specified
Output
Input
Input
Input
A
0
thru A
7
Input
B
0
thru B
7
Input
Isolation
Store A and B Data
Store A, Hold B
Store A in Both Registers
Hold A, Store B
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
Operating Mode
H = HIGH Voltage Level
L = LOW Voltage Level
X = 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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