Philips Semiconductors

Product specification

74LVC646A

Octal bus transceiver/register (3-State)

1998 Jul 29

3

PIN CONFIGURATION

SV00766

1

2

3

4

5

6

7

8

9

10

11

12

CP AB

S AB

DIR

A 0

A 1

A 2

A 3

A 4

A 5

A 6

A 7

GND

V CC

CP BA

S BA

OE

B 0

B 1

B 2

B 3

B 4

B 5

B 6

B 7

24

23

22

21

20

19

18

17

16

15

14

13

PIN DESCRIPTION

PIN NUMBER

SYMBOL

FUNCTION

1

‘A’ to ‘B’ clock input

(LOW-to-HIGH, edge-triggered)

2

Select ‘A’ to ‘B’ source input

3

DIR

Direction control input

4, 5, 6, 7, 8,

9, 10, 11

‘A’ data inputs/outputs

12

GND

Ground (0V)

20, 19, 18, 17,

16, 15, 14, 13

‘B’ data inputs/outputs

21

OE

Output enable input (active LOW)

22

Select ‘B’ to ‘A’ source input

23

‘B’ to ‘A’ clock input

(LOW-to-HIGH, edge-triggered)

24

Positive supply voltage

FUNCTION TABLE

INPUTS

DATA I/O *

FUNCTION

OE

DIR

FUNCTION

X

X

X

X

↑

X

X

↑

X

X

X

X

input

un *

un *

input

store A, B unspecified *

store B, A unspecified *

H

H

X

X

↑

H or L

↑

H or L

X

X

X

X

input

input

store A and B data,

isolation hold storage

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

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

*

The data output functions may be enabled or disabled by

various signals at the OE and DIR inputs. Data input

functions are always enabled, i.e., data at the bus inputs will

be stored on every LOW-to-HIGH transition on the clock

inputs.

un

= unspecified

H

= HIGH voltage level

L

= LOW voltage level

X

= Don’t care

↑

= LOW-to-HIGH level transition