3

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Function Table

H

= HIGH Voltage Level

L

= LOW Voltage Level

X

= Immaterial

 = 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. This also applies to data I/O (A and B: 8–15) and #2 control pins.

Logic Diagrams

Please note that these diagrams are provided only for the understanding of logic operations and should not be used to estimate propagation delays.

Inputs

Inputs/Outputs (Note 1)

Operating Mode

L

H

H or L

H or L

X

X

Input

Input

Isolation

L

H





X

X

Store A and B Data

X

H



H or L

X

X

Input

Not Specified

Store A, Hold B

H

H





X

X

Input

Output

Store A in Both Registers

L

X

H or L



X

X

Not Specified

Input

Hold A, Store B

L

L





X

X

Output

Input

Store B in Both Registers

L

L

X

X

X

L

Output

Input

Real-Time B Data to A Bus

L

L

X

H or L

X

H

Store B Data to A Bus

H

H

X

X

L

X

Input

Output

Real-Time A Data to B Bus

H

H

H or L

X

H

X

Stored A Data to B Bus

H

L

H or L

H or L

H

H

Output

Output

Stored A Data to B Bus and

Stored B Data to A Bus