I2C Clocking and power considerations

The Master function of the I^ 2C always requires a peripheral clock to be running in order to operate. The Slave function can operate without any internal clocking when the slave is not currently addressed. This means that reduced power modes up to Power-down mode can be entered, and the device will wake up when the I^ 2C Slave function recognizes an address. Monitor mode can similarly wake up the device from a reduced power mode when information becomes available.