PCA9673PW datasheet(8/33 Pages) PHILIPS

8 / 33 page

PCA9673_1

Product data sheet

Rev. 01 — 1 February 2007

8 of 33

NXP Semiconductors

PCA9673

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

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 0 (write)

is sent by the I2C-bus master.

3. The PCA9673 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 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 PCA9673 acknowledges this value only. If the byte is not equal to 06h, the

PCA9673 does not acknowledge it.

If more than 1 byte of data is sent, the PCA9673 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 PCA9673 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.

The I2C-bus master must interpret a non-acknowledge from the PCA9673 (at any time) as

a ‘Software Reset Abort’. The PCA9673 does not initiate a reset of its registers.

The unique sequence that initiates a Software Reset is described in Figure 12.

7.2.2 Device ID (PCA9673 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, PCA9673 16-bit

quasi-output I/O expander).

Fig 12. Software Reset sequence

002aac307

SWRST Call I2C-bus address

START condition

R/W

acknowledge

from slave(s)

SWRST data = 06h

acknowledge

from slave(s)

PCA9673 is(are) reset.

Registers are set to default power-up values.

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