TCA9548A in multi-master setup

Hi Dewey,
I will be happy to help you.

1. If more than one channel is enabled, can devices on downstream channels communicate with each other through the switch?
TCA9548A switching device is a passive FET switch with I2C core. Once you enable the FET switches using the I2C programming from SCL/SDA, slaves on downstream channels can talk to each other

2. If a master device is placed on a downstream channel, can it address the switch and enable/disable channels?
The downstream channels do not have the capability to control the passive FET switches. So, the downstream master cannot change which switch to turn on/off.

Thanks,
Rajan

Thanks for the quick reply Rajan,

Just out of curiosity, how does the I2C core differentiate a command sent from the upstream channel from one sent from a downstream channel, as the two channels are connected together by the FET? Perhaps the block diagram in the documentation is too simplistic in this regard.

Thanks,

Dewey

Dewey,
This is an interesting question. For the switch that is already connected by the main master, you can actually have the downstream bus control the I2C core, since as you mentioned the FET is already on, and the two SCL's and SDA's are connected. For the switches that are off, the downstream bus cannot control the I2C core. Have you tried experimenting with this topology on a board?

Thanks,
Rajan

I have not tried this yet, I'm looking into using this chip on a multi-master bus and just want to figure out all the details.

Thanks,

Dewey

Dewey,
Ok.. It will be possible to do this. During power-on reset the TCA9545A will reset to its default state, so you will have to use the upstream master bus to control the TCA9545A again before the downstream bus will be able to communicate.

Thanks,
Rajan