TCA9545A: TCA9545A: VCC rising time unknown state

user5865991 said:

Part Number: TCA9545A

Dear Bobby

 

I’m inoue.

Thank you for answer the "TCA9545A: VCC rising time".

I have additional three questions.

＞a bad PoR causing the state machine of the device to start up in an unknown state

 

 　1)If the device starts up in an unknown state,

       Is the state fixed after sending the first Read or Write command?

It should be able to be fixed by doing a write to all the registers by setting the default values back into the writable registers.

 

＞Toggling the SCL pin 8 times should resolve the issue but is not a 100% guarantee.

 

 　2)What are the concerns that are not 100%?
        The state machine is in an unknown state which it was not designed to be in. In this case (I've never seen this occur though) I would guess there is a possibility it would ignore the 8 clock pulses.... There have not been any reported issues of this happening... I would suggest another power cycle or toggling reset if this did occur.

 　3)What should be the SDA state when the SCL is toggled 8 times? Don’t care?

        The TCA9545A may latch the SDA line low if it powers up and the state machine thinks it is ACKing. A clock pulse should resolve that. You should perform a stop condition after 8 pulses though.

 

Inoue

Comments provided in bold above.

-Bobby

Dear Bobby

Thank you for answer.

-Inoue