PCA9675 Datasheet, PDF (10/34 Pages) NXP Semiconductors – Remote 16-bit I/O expander for Fm+ I2C-bus with interrupt

NXP Semiconductors
PCA9675
Remote 16-bit I/O expander for Fm+ I²C-bus with interrupt
The I²C-bus master must interpret a non-acknowledge from the PCA9675 (at any time) as
a ‘Software Reset Abort’. The PCA9675 does not initiate a reset of its registers.
The unique sequence that initiates a Software Reset is described in Figure 12.
SWRST Call I²C address
SWRST data = 06h
S0 0 0 0 0 0 0 0A0 0 0 0 0 1 1 0AP
START condition
R/W
acknowledge
acknowledge
from slave(s)
from slave(s)
PCA9675 is(are) reset.
Registers are set to default power-up values.
002aac156
Fig 12. Software Reset sequence
7.2.2 Device ID (PCA9675 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 Semiconductors).
• 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, PCA9675 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, hard wired 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.
PCA9675_1
Product data sheet
Rev. 01 — 1 February 2007
© NXP B.V. 2007. All rights reserved.
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