PI74LCX646

PI74LCX652

3.3V 8-BIT REGISTERED TRANSCEIVER

2

PS2104A 02/07/97

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Inputs

DATA I/O

(2)

Function/Operation

GAB

GBA

CPAB

CPBA

SAB

SBA

A0-A7

B0-B7

Isolation

L

H

H or L

H or L

X

X

Input

Input

Store A and B Data

L

H

↑↑

XX

Store A, Hold B

X

H

↑

H or L

X

X

Input

Store A in Both Registers

H

H

↑↑

X

(2)

X

Input

Output

Hold A, Store B

L

X

H or L

↑

X

X

Input

Store B in Both Registers

L

L

↑↑

XX

(2)

Output

Input

Real Time B Data to A Bus

L

L

X

X

X

L

Output

Input

Stored B Data to A Bus

L

L

X

H or L

X

H

Real Time A Data to B Bus

H

H

X

X

L

X

Input

Output

Stored A Data to B Bus

H

H

H or L

X

H

X

Stored A Data to B Bus and

H

L

H or L

H or L

H

H

Output

Output

Stored B Data to A Bus

Pin Name

Description

Data Register A Inputs

Data Register B Outputs

Data Register B Inputs

Data Register A Outputs

CPAB, CPBA

Clock Pulse Inputs

SAB, SBA

Output Data Source SelectInputs

DIR, G

Output Enable Inputs (LCX646)

GAB, GBA

Output Enable Inputs (LCX652)

GND

Ground

Power

Product Pin Description

CPAB

SAB

DIR

GND

CPBA

SBA

G

24-PIN

H24

L24

Q24

S24

PI74LCX646

Product Pin Configuration

CPAB

SAB

GAB

GND

CPBA

SBA

GBA

24-PIN

H24

L24

Q24

S24

PI74LCX652

Product Pin Configuration

PI74LCX646 Truth Table

Inputs

DATA I/O

(2)

Function/Operation

G

DIR

CPAB

CPBA

SAB

SBA

A0-A7

B0-B7

Isolation

H

X

H or L

H or L

X

X

Input

Input

Store A and B Data

H

X

↑↑

XX

Real Time B Data to A Bus

L

L

X

X

X

L

Output

Input

Stored B Data to A Bus

L

L

X

H or L

X

H

Real Time A Data to B Bus

L

H

X

X

L

X

Input

Output

Stored A Data to B Bus

L

H

H or L

X

H

X

PI74LCX652 Truth Table

Notes:

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 to load both registers.

H = High Voltage Level; L = Low Voltage Level; X = Don't Care;

↑ = LOW-to-HIGH transition

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13