I am reading through the Device Profile and noticed a reference to a 32 KHz crystal in the Accumulated Crank Period section. It seems like using a crystal is almost a necessity based on the rollover value of 2048s. I know that the MSP430's source 32 KHz from an external crystal through ACLK. I would be nice to be a able to use the DCO if possible to avoid the external crystal but maybe it's not accurate enough? I am pretty new to this stuff so I was hoping someone could validate my thoughts.
The profile just specifies the units of time in which the values need to be encoded, but the specific crystal implementation is up to your own design, as long as you convert the time to the proper units.