100kHz I2C device in 400kHz clock environment.

[spktu]

400 khz clock

What will be the behaviour of I2C device capable of only 100kHz clock in 400kHz clock environment?

 

[VVV]

a i2c 400khz works with 100khz bus

Most likely it will not work. It may not have enough time to move the data internally, since it was designed to work at lower speed.

 

[spktu]

i2c 400khz to 100khz

I can change clock to 100kHz when addressing 100kHz device.
But when I address to 400kHz devices on the same I2C bus, what will be the behaviour of 100kHz devices?
I am afraid , that they will behave unpredictably even though they are not addressed, but just because the clock is 400kHz.
Am I right?

 

[VVV]

That is the most likely scenario.
I would not change the bus rate. If I remember correctly, the I2C bus specification does not allow it. All the devices on the bus must run at the same rate.