This disclosure is directed to the synchronization of clocks of a secondary implantable medical device (IMD) to a clock of a primary IMD. The secondary IMD includes a communications clock. The communications clock may be synchronized based on at least one received communications pulse. The secondary IMD further includes a general purpose clock different than the communications clock. The general purpose clock may be synchronized based on at least one received power pulse. The communications clock may also be synchronized based on the at least one received power pulse.