PCA9633DP2 datasheet(17/43 Pages) NXP

17 / 43 page

PCA9633_5

Product data sheet

Rev. 05 — 25 July 2008

17 of 43

NXP Semiconductors

PCA9633

4-bit Fm+ I2C-bus LED driver

7.6 Software Reset

The Software Reset Call (SWRST 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 SWRST Call function is deﬁned as the following:

1. A START command is sent by the I2C-bus master.

2. The reserved SWRST I2C-bus address ‘0000 011’ with the R/W bit set to 0 (write) is

sent by the I2C-bus master.

3. The PCA9633 device(s) acknowledge(s) after seeing the SWRST Call address

‘0000 0110’ (06h) only. If the R/W bit is set to 1 (read), no acknowledge is returned to

the I2C-bus master.

4. Once the SWRST Call address has been sent and acknowledged, the master sends

2 bytes with 2 speciﬁc values (SWRST data byte 1 and byte 2):

a. Byte 1 = A5h: the PCA9633 acknowledges this value only. If byte 1 is not equal to

A5h, the PCA9633 does not acknowledge it.

b. Byte 2 = 5Ah: the PCA9633 acknowledges this value only. If byte 2 is not equal to

5Ah, then the PCA9633 does not acknowledge it.

If more than 2 bytes of data are sent, the PCA9633 does not acknowledge any more.

5. Once the right 2 bytes (SWRST data byte 1 and byte 2 only) have been sent and

correctly acknowledged, the master sends a STOP command to end the SWRST Call:

the PCA9633 then resets to the default value (power-up value) and is ready to be

addressed again within the speciﬁed bus free time (tBUF).

The I2C-bus master must interpret a non-acknowledge from the PCA9633 (at any time) as

a ‘SWRST Call Abort’. The PCA9633 does not initiate a reset of its registers. This

happens only when the format of the SWRST Call sequence is not correct.

PCA9633DP2 Datasheet(PDF) 17 Page - NXP Semiconductors