PCA9641PW datasheet(30/55 Pages) NXP

30 / 55 page

PCA9641

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Product data sheet

Rev. 2.1 — 27 October 2015

30 of 55

NXP Semiconductors

PCA9641

2-channel I2C-bus master arbiter

13. General call software reset

The Software Reset Call allows all the devices in the I2C-bus to be reset to the power-up

state value through a specific formatted I2C-bus command. To be performed correctly, it

implies that the I2C-bus is functional and that there is no device hanging the bus.

The Software Reset sequence is defined as following:

1. A START command is sent by the I2C-bus master.

2. The reserved General Call I2C-bus address ‘0000 000’ with the R/W bit set to 0 (write)

is sent by the I2C-bus master.

3. The device(s) acknowledge(s) after seeing the General Call address ‘0000 0000’

(00h) only. If the R/W bit is set to 1 (read), no acknowledge is returned to the I2C-bus

master.

4. Once the General Call address has been sent and acknowledged, the master sends

1 byte. The value of the byte must be equal to 06h. The device acknowledges this

value only. If the byte is not equal to 06h, the device does not acknowledge it. If more

than 1 byte of data is sent, the device does not acknowledge any more.

5. Once the right byte has been sent and correctly acknowledged, the master sends a

STOP command to end the Software Reset sequence: the slave device then resets to

the default value (power-up value) and is ready to be addressed again within the

specified bus free time. If the master sends a Repeated START instead, no reset is

performed.

6. PCA9641 will issue the bus recovery procedure.

The I2C-bus master must interpret a non-acknowledge from the slave device (at any time)

as a ‘Software Reset Abort’. Slave device does not initiate a reset of its registers.

1000 0101

INT_MASK

MB_LO

MB_HI

CONTR

STATUS

INT_

STATUS

1000 0110

MB_LO

MB_HI

CONTR

STATUS

INT_

STATUS

INT_MASK

1000 0111

MB_HI

CONTR

STATUS

INT_

STATUS

INT_MASK

MB_LO

Table 15.

Read/write the registers using Auto-Increment …continued

Command

code

First

data byte

Second

data byte

Third

data byte

Fourth

data byte

Fifth

data byte

Sixth

data byte

Seventh

data byte

Eighth

data byte

Fig 18. Software Reset sequence

aaa-008555

SWRST Call I2C-bus address

START condition

R/W

acknowledge

from slave(s)

SWRST data = 06h

acknowledge

from slave(s)

PCA9641 is reset.

Registers are set to default power-up values.

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