PCA9641PW datasheet(34/55 Pages) NXP

34 / 55 page

PCA9641

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Product data sheet

Rev. 2.1 — 27 October 2015

34 of 55

NXP Semiconductors

PCA9641

2-channel I2C-bus master arbiter

16.1 Specific applications

The PCA9641 is a 2-to-1 I2C-bus master arbiter designed for dual masters sharing the

same downstream slave devices. Any master can request the downstream bus at any

time and PCA9641 will let the master know when it is its turn to control the downstream

bus. The master will not overwrite the other master’s transactions, and no advance

software is needed. In high reliability I2C-bus applications, the PCA9641 will switch

between masters when the downstream bus is free and clear. If the downstream bus

hangs, PCA9641 will remotely recover the bus by multiple ways, such as smart

initialization, SMBus time-out, remote toggling of SCL and SDA.

16.2 High reliability systems

In a typical multipoint application, shown in Figure 22, the two masters (for example,

primary and back-up) are located on separate I2C-buses that connect to multiple

downstream I2C-bus slave cards/devices via a PCA9641 for non-hot swap applications to

provide high reliability of the I2C-bus.

I2C-bus commands are sent via the primary or back-up master and either master can take

command of the I2C-bus. Either master at any time can gain control of the slave devices if

the other master is disabled or removed from the system. The failed master is isolated

from the system and will not affect communication between the on-line master and the

slave devices located on the cards.

For even higher reliability in multipoint backplane applications, two dedicated masters can

be used for every card as shown in Figure 23.

Fig 21. Arbitration application

aaa-009751

Master 0

M0-Trans3

M0-Trans2

M0-Trans1

I2C M0

PCA9641

ARBITER

I2C M1

M0-Trans1

M1-Trans2

Master 1

M0-Trans3

M1-Trans2

Slave 1

Slave 0

M0-Trans2

M0-Trans1

Slave 2

Slave 3

Slave 4

M0-Trans1

Fig 22. High reliability backplane application

002aag820

SCL1

SDA1

SCL0

SDA0

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