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PCA9674_PCA9674A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 7 — 30 May 2013 11 of 40
NXP Semiconductors
PCA9674; PCA9674A
Remote 8-bit I/O expander for Fm+ I
2
C-bus with interrupt
7.2 Software Reset Call, and device ID addresses
Two other different addresses can be sent to the PCA9674; PCA9674A.
• General Call address: allows to reset the PCA9674; PCA9674A through the I
2
C-bus
upon reception of the right I
2
C-bus sequence. See Section 7.2.1 “Software Reset” for
more information.
• Device ID address: allows to read ID information from the device (manufacturer, part
identification, revision). See Section 7.2.2 “
Device ID (PCA9674; PCA9674A ID field)”
for more information.
7.2.1 Software Reset
The Software Reset Call allows all the devices in the I
2
C-bus to be reset to the power-up
state value through a specific formatted I
2
C-bus command. To be performed correctly, it
implies that the I
2
C-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 I
2
C-bus master.
2. The reserved General Call I
2
C-bus address ‘0000 000’ with the R/W bit set to 0 (write)
is sent by the I
2
C-bus master.
3. The PCA9674; PCA9674A 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 I
2
C-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.
a. The PCA9674; PCA9674A acknowledges this value only. If the byte is not equal to
06h, the PCA9674; PCA9674A does not acknowledge it.
If more than 1 byte of data is sent, the PCA9674; PCA9674A 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 PCA9674; PCA9674A
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.
Fig 7. General Call address
Fig 8. Device ID address
0
002aac115
0 0 0 0 0 0 0
R/W