Failsafe backup mode in an implantable medical device

A method for use with an implantable medical device (IMD) that includes a processor, a counter, a non-volatile memory (NVM) that stores backup mode firmware, and a random access memory (RAM) that includes multiple separate RAM blocks, the method comprising:

• monitoring for and detecting a malfunction that when detected should cause the IMD to operate in accordance with a backup mode;
• in response to the malfunction being detected, performing a device reset operation of the IMD, incrementing the counter, and the processor executing the backup mode firmware and thereby operating the IMD in accordance with the backup mode;
• and
• while the processor is executing the backup mode firmware and thereby operating the IMD in accordance with the backup mode, the processor storing and accessing variables in one of the RAM blocks identified using the counter following the incrementing of the counter.

An implantable medical device (IMD), comprising:

• a non-volatile memory (NVM) that stores backup mode firmware;
• a random access memory (RAM) that includes multiple separate RAM blocks;
• a processor that executes the backup mode firmware to operate the IMD in accordance with a backup mode, wherein when the processor operates the IMD in the backup mode the processor stores and accesses variables in one of the RAM blocks;
• and
• a counter that is selectively incremented after a reset operation and used to select which one of the RAM blocks the variables are stored within while the processor operates the IMD in the backup mode.