Datasheet
PCA9670 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 3 — 30 May 2013 8 of 35
NXP Semiconductors
PCA9670
Remote 8-bit I/O expander for Fm+ I
2
C-bus with reset
7.2 Software Reset Call, and device ID addresses
Two other different addresses can be sent to the PCA9670.
• General Call address: allows resetting the PCA9670 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 reading ID information from the device (manufacturer, part
identification, revision). See Section 7.2.2 “
Device ID (PCA9670 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 PCA9670 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 PCA9670 acknowledges this value only. If the byte is not equal to 06h, the
PCA9670 does not acknowledge it.
If more than 1 byte of data is sent, the PCA9670 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 PCA9670 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
R/W
002aac116
1 1 1 1 1 0 0