A leadless pacemaker, and method for storing event data therein, comprising a central processing unit, a first logic circuit configured to generate event data based on a first event occurring during operation of the leadless pacemaker, a first hardware event counter configured to be incremented if specific event data are generated by said first logic circuit, a first memory unit comprising a first bit configured to be set if said first hardware event counter is incremented to a first maximum number of counts, a second memory unit communicating with said first memory unit, wherein said central processing unit is configured to transfer said first bit to said second memory unit, a first RAM event counter in a random access memory of said leadless pacemaker, wherein said central processing unit is configured to increment said first RAM event counter if said first bit is transferred to the second memory unit.