IDT54/74FCT646/2646/652/2652T/AT/CT/DT, 648T/AT/CT

FAST CMOS OCTAL TRANSCEIVER/REGISTER

MILITARY AND COMMERCIAL TEMPERATURE RANGES

6.20

3

FUNCTION TABLE (646/648)

FUNCTION TABLE (652)

Inputs

Operation or Function

G

G

DIR

CPAB

CPBA

SAB

SBA

FCT646T/FCT2646T

FCT648T

H

H

X

X

H or L

↑

H or L

↑

X

X

X

X

Input

Input

Isolation

Store A and B Data

Isolation

Store A and B Data

L

L

L

L

X

X

X

H or L

X

X

L

H

Output

Input

Real-Time B Data to A Bus

Stored B Data to A Bus

Real-Time

B Data to A Bus

Stored

B Data to A Bus

L

L

H

H

X

H or L

X

X

L

H

X

X

Input

Output

Real-Time A Data to B Bus

Stored A Data to B Bus

Real-Time

A Data to B Bus

Stored

A Data to B Bus

2634 tbl 02

Inputs

Data I/O

Operation or Function

GAB

GBA

GBA CPAB CPBA SAB SBA

FCT652T/FCT2652T

L

L

H

H

H or L

↑

H or L

↑

X

X

X

X

Input

Input

Isolation

Store A and B Data

X

H

H

H

↑

↑

H or L

↑

X

X

X

Input

Input

Output

Store A, Hold B

Store A in Both Registers

L

L

X

L

H or L

↑

↑

↑

X

X

X

Output

Input

Input

Hold A, Store B

Store B in Both Registers

L

L

L

L

X

X

X

H or L

X

X

L

H

Output

Input

Real-Time B Data to A Bus

Stored B Data to A Bus

H

H

H

H

X

H or L

X

X

L

H

X

X

Input

Output

Real-Time A Data to B Bus

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

NOTES:

2634 tbl 03

1. The data output functions may be enabled or disabled by various signals at the GAB or 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.

2. Select control = L: clocks can occur simultaneously.

Select control = H: clocks must be staggered in order to load both registers.

H = HIGH, L = LOW, X = Don't Care,

≠ = LOW-to-HIGH transition.

3.

A in B Register.

4.

B in A Register.