Functional Description

In the transceiver mode data present at the HIGH imped-

ance port may be stored in either the A or B register or both

The select (SAB SBA) controls can multiplex stored and

real-time

The examples in

Figure 1 demonstrate the four fundamental

bus-management functions that can be performed with the

Octal bus transceivers and receivers

Data on the A or B data bus or both can be stored in the

internal D flip-flop by LOW to HIGH transitions at the appro-

priate Clock Inputs (CPAB CPBA) regardless of the Select

or Output Enable Inputs When SAB and SBA are in the real

time transfer mode it is also possible to store data without

using the internal D flip-flops by simultaneously enabling

OEAB and OEBA In this configuration each Output reinforc-

es its Input Thus when all other data sources to the two

sets of bus lines are in a HIGH impedance state each set of

bus lines will remain at its last state

Note A Real-Time

Transfer Bus B to Bus A

TLF9581 – 6

OEAB

OEBA

CPAB

CPBA

SAB

SBA

LL

X

X

X

L

Note B Real-Time

Transfer Bus A to Bus B

TLF9581 – 7

OEAB

OEBA

CPAB

CPBA

SAB

SBA

HHX

X

L

X

Note C Storage

TLF9581 – 8

OEAB

OEBA

CPAB

CPBA

SAB

SBA

XH

L

XX

X

LX

X

L

XX

LH

LL

XX

Note D Transfer Storage

Data to A or B

TLF9581 – 9

OEAB

OEBA

CPAB

CPBA

SAB

SBA

H

L

HorL

HorL

H

X

FIGURE 1

Inputs

InputsOutputs (Note 1)

Operating Mode

OEAB

OEBA

CPAB

CPBA

SAB

SBA

L

H

HorL

HorL

X

X

Input

Input

Isolation

LH

LL

X

X

Store A and B Data

XH

L

H or L

X

X

Input

Not Specified

Store A Hold B

HH

LL

X

X

Input

Output

Store A in Both Registers

L

X

HorL

L

X

X

Not Specified

Input

Hold A Store B

LL

LL

X

X

Output

Input

Store B in Both Registers

LL

X

X

X

L

Output

Input

Real-Time B Data to A Bus

L

L

X

H or L

X

H

Store B Data to A Bus

HHX

X

L

X

Input

Output

Real-Time A Data to B Bus

H

H

H or L

X

H

X

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

Note 1

The data output functions may be enabled or disabled by various signals at OEAB or OEBA inputs Data input functions are always enabled ie data at the

bus pins will be stored on every LOW to HIGH transition on the clock inputs

4