PCA9674ATS datasheet(12/34 Pages) PHILIPS

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PCA9674_PCA9674A_2

Product data sheet

Rev. 02 — 12 October 2006

12 of 34

NXP Semiconductors

PCA9674/74A

Remote 8-bit I/O expander for Fm+ I2C-bus with interrupt

7.2.2 Device ID (PCA9674/74A ID ﬁeld)

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

• 8 bits with the manufacturer name, unique per manufacturer (for example, NXP).

• 13 bits with the part identiﬁcation, assigned by manufacturer, the 7 MSBs with the

category ID and the 6 LSBs with the feature ID (for example, for example

PCA9674/74A 16-bit quasi-output I/O expander).

• 3 bits with 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 8 manufacturer bits (ﬁrst byte +

4 MSB of the second byte), followed by the 13 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

PCA9674/74A rolls back to the ﬁrst byte and keeps sending the Device ID sequence

until a NACK has been detected.

For the PCA9674/74A, the Device ID is as shown in Figure 12.

Fig 12. PCA9674/74A ID

002aac118

revision

part identification

manufacturer

category identification

feature identification

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