2

Functional Diagram

FUNCTION TABLE

INPUTS

DATA I/O

OPERATION OR FUNCTION

OEAB

OEBA

CAB

CBA

SAB

SBA

A0 THRU A7

B0 THRU B7

651

652

L

H

H or L

H or L

X

X

Input

Input

Isolation (Note 1)

Isolation (Note 1)

LH

↑↑

X

X

Store A and B Data

Store A and B Data

XH

↑

H or L

X

X

Input

Unspecified

(Note 2)

Store A, Hold B

Store A, Hold B

HH

↑↑

X

(Note 3)

X

Input

Output

Store A in Both

Registers

Store A in Both

Registers

L

X

H or L

↑

X

X

Unspecified

(Note 2)

Input

Hold A, Store B

Hold A, Store B

LL

↑↑

XX

(Note 3)

Output

Input

Store B in Both

Registers

Store B in Both

Registers

L

L

X

X

X

L

Output

Input

Real-Time B Data to

A Bus

Real-Time B Data to

A Bus

L

L

X

H or L

X

H

Stored B Data to A

Bus

Stored B Data to A

Bus

H

H

X

X

L

X

Input

Output

Real-Time A Data to

B Bus

Real-Time A Data to

B Bus

H

H

H or L

X

H

X

Stored 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 A Data to B

Bus

Stored B Data to A

Bus

Stored B Data to A

Bus

NOTES:

1. To prevent excess currents in the High-Z (isolation) modes, all I/O terminals should be terminated with 10k

Ω to 1MΩ resistors.

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

3. Select Control = L: Clocks can occur simultaneously.

Select Control = H: Clocks must be staggered in order to load both registers.

20

19

18

17

15

13

14

16

4

B0

B1

B2

B3

B4

B5

B6

B7

OEBA

OEAB

21

3

6

11

5

7

8

9

10

A0

A1

A2

A3

A4

A5

A6

A7

1

23

2

22

CAB CLOCK

CBA CLOCK

SAB SOURCE

SBA SOURCE

GND = PIN 12

VCC = PIN 24

B

DATA

PORT

A

DATA

PORT

FLIP-FLOP

CLOCKS

DATA

SOURCE

SELECTION

INPUTS

CD74HC652, CD74HCT652

CD74HC652, CD74HCT652