Philips Semiconductors

Product specification

74F651A/74F652A

Transceivers/registers

1999 Jun 23

5

The following examples demonstrate the four fundamental

bus-management functions that can be performed with the 74F651A

and 74F652A. The select pins determine whether data is stored or

transferred through the device in real time. The output enable pins

determine the direction of the data flow.

BUS MANAGEMENT FUNCTIONS

REAL TIME BUS TRANSFER

BUS B TO BUS A

REAL TIME BUS TRANSFER

BUS A TO BUS B

STORAGE FROM

A, B, OR A AND B

TRANSFER STORED DATA

TO A AND/OR B

OEAB OEBA CPAB CPBA SAB SBA

OEAB OEBA CPAB CPBA SAB SBA

OEAB OEBA CPAB CPBA SAB SBA

OEAB OEBA CPAB CPBA SAB SBA

BUS A

BUS A

BUS A

BUS A

BUS B

BUS B

BUS B

BUS B

SF00409

L

L

X

X

X

L

H

H

XXL

X

X

H

↑

XX

X

LX

X

↑

XX

LH

↑↑

XX

H

L

H or L H or L

H

H

FUNCTION TABLE

INPUTS

DATA I/O

OPERATING MODE

OEAB

OEBA

CPAB

CPBA

SAB

SBA

An

Bn

74F651A

74F652A

L

H

H or L

H or L

X

X

Input

Input

Isolation

Isolation

L

H

↑

↑

X

X

Input

Input

Store A and B data

Store A and B data

X

H

↑

H or L

X

X

Input

Unspecified*

Store A, hold B

Store A hold B

H

H

↑

↑

L

X

Input

Output

Store A in both registers

Store A in both registers

L

X

H or L

↑

X

X

Unspecified*

Input

Hold A, store B

Hold A, store B

L

L

↑

↑

X

L

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

Output

Input

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

Input

Output

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

Stored A data to B bus

H

L

H or L

H or L

H

H

Output

Output

Stored B data to A bus

Stored B data to A bus

Notes to function table

1. H = High-voltage level

2. L

= Low-voltage level

3. *

= The data output function may be enabled or disabled by various signals at the OEBA and OEAB inputs. Data input functions are

always enabled, i.e., data at the bus pins will be stored on every low-to-high transition of the clock.

4.

↑ = Low-to-high clock transition

5. X = Don’t care