what's the application scenario of the CPUDIV in CLK?

[l yk]

We can get the information that the CPUDIV can be used to divide fMATESR for CPU. And the divide ration can up to 128：1. I wonder that when you configure CPUDIV to 128:1, can CPU works normally when access peripherals such as I2C. Or CPUDIV is just for some special scenario?