PCA9671DB datasheet(9/35 Pages) NXP

9 / 35 page

PCA9671

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Product data sheet

Rev. 2 — 29 July 2010

9 of 35

NXP Semiconductors

PCA9671

Remote 16-bit I/O expander for Fm+ I2C-bus with reset

7.2 Software Reset call, and device ID addresses

Two other different addresses can be sent to the PCA9671.

• General Call address: allows to reset the PCA9671 through the I2C-bus upon

reception of the right I2C-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 (PCA9671 ID field)” for more

information.

7.2.1 Software Reset

The Software Reset Call allows all the devices in the I2C-bus to be reset to the power-up

state value through a specific formatted I2C-bus command. To be performed correctly, it

implies that the I2C-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 I2C-bus master.

2. The reserved General Call I2C-bus address ‘0000 000’ with the R/W bit set to logic 0

(write) is sent by the I2C-bus master.

3. The PCA9671 device(s) acknowledge(s) after seeing the General Call address

‘0000 0000’ (00h) only. If the R/W bit is set to logic 1 (read), no acknowledge is

returned to the I2C-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 PCA9671 acknowledges this value only. If the byte is not equal to 06h, the

PCA9671 does not acknowledge it.

If more than 1 byte of data is sent, the PCA9671 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 PCA9671 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 10. General Call address

Fig 11. Device ID address

002aac155

R/W

002aab638

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