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TCA9534A: Decoding Adress

Part Number: TCA9534A
Other Parts Discussed in Thread: TCA9555

Can you change the address of the TCA9534A when its powered on by changing the state of the address pins or can this only be changed when the device is powered on. If it can not be changed when it is powered on does TI make a GPIO expander that has this ability?

  • Hey Andrew,

    It's funny you bring this up. I am working on a technical document which discusses this, (dynamic addressing). We've found that in some rare instances, designers run out of I2C addresses and rather than using I2C switches (sometimes the switches themselves do not have unique addresses!) they would prefer to dynamically change the address.

    "Can you change the address of the TCA9534A when its powered on by changing the state of the address pins or can this only be changed when the device is powered on?"

    I've done testing on our TCA9555 to verify if the address pins latched upon start up or if the device was dynamically addressable. I found that the TCA9555 was indeed dynamically addressable (address is not latched) so a reset was NOT necessary to communicate with the device over I2C when changing the address pins after power up. Now I know your question was specifically for TCA9534A however I talked to some other peers who have supported these devices for much longer than I and found that the digital cores of all the I2C devices should all be identical. This means if TCA9555 is dynamically addressable then TCA9534A should also be dynamically addressable.

    Thanks,

    -Bobby