PCA9641PW datasheet(31/55 Pages) NXP

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PCA9641

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Product data sheet

Rev. 2.1 — 27 October 2015

31 of 55

NXP Semiconductors

PCA9641

2-channel I2C-bus master arbiter

14. Device ID (PCA9641 ID field)

The Device ID field is a 3-byte read-only (24 bits) word giving the following information:

• The first 12 bits are for the manufacturer name, unique per manufacturer (for

example, NXP).

• The next 9 bits are for the part identification, assigned by manufacturer.

• The last 3 bits are for the die revision, assigned by manufacturer (for example,

Rev X).

The Device ID is read-only, hardwired in the device and can be accessed as follows:

1. START command.

2. The master sends the Reserved Device ID I2C-bus address ‘1111 100’ with the R/W

bit set to 0 (write).

3. The master sends the I2C-bus slave address of the slave device it needs to identify.

The LSB is a ‘Don’t care’ value. Only one device must acknowledge this byte (the one

that has the I2C-bus slave address).

4. The master sends a Re-START command.

Remark: A STOP command followed by a START command will reset the slave state

machine and the Device ID read cannot be performed.

Remark: A STOP command or a Re-START command followed by an access to

another slave device will reset the slave state machine and the Device ID read cannot

be performed.

5. The master sends the Reserved Device ID I2C-bus address ‘1111 100’ with the R/W

bit set to 1 (read).

6. The device ID read can be done, starting with the 12 manufacturer bits

(first byte + 4 MSB of the second byte), followed by the 9 part identification bits and

then the 3 die revision bits (3 LSB of the third byte).

7. The master ends the reading sequence by NACKing the last byte, thus resetting the

slave device state machine and allowing the master to send the STOP command.

Remark: The reading of the Device ID can be stopped anytime by sending a NACK

command.

Remark: If the master continues to ACK the bytes after the third byte, the PCA9641

rolls back to the first byte and keeps sending the Device ID sequence until a NACK

has been detected.

Table 16.

PCA9641 ID field

Byte 3

Byte 2

Byte 1

000

001

0000

011

100

Bits [23:11]

Bits [10:3]

Bits [2:0]

Manufacturer ID

Part ID

Revision

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