Datasheet

PCA9570 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 4 — 17 September 2014 7 of 32
NXP Semiconductors
PCA9570
Remote 4-bit general purpose outputs for 1 MHz I
2
C-bus
7.2.2 Device ID (PCA9570 ID field)
The Device ID field is a 3 byte read-only (24 bits) word giving the following information:
• 12 bits with the manufacturer name, unique per manufacturer (for example, NXP).
• 9 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 PCA9570 4-bit 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 I
2
C-bus address followed by the R/W bit
set to 0 (write): ‘1111 1000’.
3. The master sends the I
2
C-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 I
2
C-bus slave address).
4. The master sends a Re-START command.
Remark: A STOP command followed by a START command resets the slave state
machine and the Device ID read cannot be performed. Also, a STOP command or a
Re-START command followed by an access to another slave device resets the slave
state machine and the Device ID Read cannot be performed.
5. The master sends the Reserved Device ID I
2
C-bus address followed by the R/W bit
set to 1 (read): ‘1111 1001’.
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 (4 LSBs of the
second byte + 5 MSBs of the third byte), and then the 3 die revision bits (3 LSBs 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.
If the master continues to ACK the bytes after the third byte, the slave rolls back to the
first byte and keeps sending the Device ID sequence until a NACK has been
detected.
For the PCA9570, the Device ID is as shown in Figure 10
.
Fig 10. PCA9570 Device ID field
0
002aag791
0 0
00 0 0 0 0 0 0
00 0 0 0 0 0 0
revision
1
0 0 0 0
part identification
manufacturer