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Original question:

PCA9536: one question about the POR function of PCA9536

PCA9536: PoR V.S. soft reset

Joseph Chao
Prodigy 20 points
Part Number: PCA9536

Sir,

I have a question about PCA9536 power-on reset, if register values are incorrect,  is it safe if write all regs right (software reset?) after power up to make sure the value is correct?  

what's the different between power-on reset and software reset ?

  • 0
    TI__Mastermind 34135 points

    Hi Joseph,

    After an internal power-on reset (POR), the device state machine and all register values will be in their defaults states. This is useful in the case of a timeout or other error where a master may be unable to reconfigure the device using a software reset. After a POR, the register may be written to their desired configuration. If the register values at start-up do not appear to match the specified default values (Table 2 of the datasheet), the POR may not have been successful. In this case, ensure that the power-on reset cycle complies with the specifications described in section 9.1 of the datasheet. 

    Let me know if this answers your question.

    Regards,
    Eric

  • 0 in reply to Eric Schott1
    Prodigy 20 points

    Hi Eric,

    I'm sorry, in the other words, if register values aren't in their default states after power up,  are there any side effect if using a software reset?

    I mean if the POR not have been successful, maybe hardware issue causing Toff < 100 ms, may I  write all registers right but doesn't power down to fix this hardware issue?

    thanks for your kindly reply.

  • 0 in reply to Joseph Chao
    TI__Mastermind 34135 points

    Hi Joseph,

    Re-initializing the device using software is fine. The advantage of using a POR is that it can clear the device's state machine in case it is caught and communication is not possible. If I2C communication is still working, configuring the device via I2C commands will not have any negative effects.

    Regards,
    Eric