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TCA9548A: Can I have standard I2C mode on few outputs and fast I2C mode on the rest

Owais Malik
Prodigy 50 points
Part Number: TCA9548A

Hi, 

I have two I2C buses on each of the output of TCA9548A switch. One output can support up to fast mode and other only supports standard mode. Can I use this TCA9548A I2C switch to isolate both I2C buses. If not then can you suggest alternate switch, Thanks

Regards

Owais

  • 0
    TI__Guru 71790 points

    Hi Owais,

    Yes, you technically can since the TCA9548A device supports fast mode and is okay with seeing standard mode traffic as well. Using a standard 2:X channel MUX/Switch can also be used if you prefer to control the channels with a select pin instead using I2C to configure the channels (TCA9548A).

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 50 points

    Just to clarify, it means that I have to set up a device with a mode I want. For example first I start with channel that is only compatible to standard mode then if I have to use another channel which support high speed, Do I need to configure the device (TCA9548) in fast mode or is it automatic sensing? Please confirm.

  • +1 in reply to Owais Malik
    TI__Guru 71790 points

    The TCA9548A doesn't know if you're operating in standard mode or fast mode. You don't have to modify any setting in the device to make it operate in either mode. 

    If you place all I2C standard mode target (slave) devices on ch0 and all I2C fast mode devices on ch1 then you would simply just enable ch0 and disable ch1 and communicate using standard mode. Then when you want to communicate using fast mode, you enable ch1 and disable ch0. You communicate to the TCA9548A in fast mode if you like, though if ch0 is enabled there could always be a chance the downstream target devices misinterprets the I2C communication since it's outside of the frequency it normally supports. 

    -Bobby