Quote Originally Posted by Bill Legge View Post
Or, can the MCU run at, say 20MHz and the 32768Hz be provided to the device from another source?
The I²C clock is usually supplied from a pin on the MCU.
Quote Originally Posted by Bill Legge View Post
The ratings for the other pins are not given in the spec sheet. Are they '5 Volt tolerant' ?
Not likely. Always assume they are not unless explicitly stated in the datasheet.