IIC Maximum Speed?

[Wings]

In the data sheet for a 9S08GT32A it says in the "features" section that the IIC module can clock as high as 100KHz, and yet the control registers allow me to set the clock frequency as high as Fbus/20. I have several peripherals that have a max clock freq of 400KHz, and that's what I want to use. What's stopping me?

I see nothing in the AC Specs about the IIC module at all.

[Techno]

IIC protocol works on the open drain configuration and although the control register allows you to configure the
IIC to work at higher frequencies but the maximum speed at which the IIC  works will depend on the load on the common SCL and SDA bus and the pad delays of these pin.
You should therefore consult the RM and check how much speed is specified for this protocol.If ur datasheet specifies 100 Khz it must be specified for some load. And one more thing IIC is a slow protocol and u have to bear with this bandwidth.

[Alban]

Hi Wings,

There's never really anything to stop you doing what you want

You may get reliability trouble in the communication. (lost frames/intermittent errors)

Also for I²C high speed the bus load is important, otherwise the signals won't be recognized.

If it is for a demo or home use you can try. If it is for production, be careful about analyzing the behaviour accross temperature and voltage to see the behaviour of the MCU and the Data/Clock lines.

I haven't done I²C for a while, but maybe the 400kHz works with additional features the module doesn't have ?

Cheers,

Alban.