program stored in a nonvolatile memory the program often is parameterized u2014 i e one or more of the operations the microprocessor performs is alterable by setting a parameter for example the microprocessor may be programmed to periodically trigger atrium stimulator 212 one of the parameters for this operation might be a value specifying the rate at which the stimulator is triggered the parameters may be provided to microprocessor 204 via telemetry module 218 and stored in memory 206 pacer 106 in fig2 uses first interval timer 208 to determine the delay between trigger signals applied to atrium stimulator 212 and ventricle stimulator 214 further second interval timer 210 measures the time since the last heartbeat sensed by the atrium sensor stimulator 212 or ventricle sensor stimulator 214 when either timer elapses the elapsed timer asserts an interrupt to microprocessor 204 to notify microprocessor 204 that the set amount of time has passed microprocessor 204 determines the source of the interrupt and takes the appropriate action for example if a maximum time has elapsed since the last heartbeat microprocessor 204 might trigger atrium sensor stimulator 212 microprocessor 204 preferably also monitors one or more physiological signals for example microprocessor 204 may detect cardiac voltage signals via atrium sensor 212 and or ventricle sensor 214 blood pressure body temperature and adaptive configuration data may also be monitored these signals preferably are logged in memory 206 for later retrieval by programmer 110 memory 206 preferably is large enough to store a.