US Patent 12135874 Live firmware update of flash memory

In described examples, a flash memory bank includes application and bootloader portions. The application portion stores first instructions for performing an interrupt service routine (ISR). The bootloader portion stores second instructions for: causing the flash memory bank to receive new first instructions for performing the ISR and write the new first instructions to replace old first instructions, and executing the new first instructions. The new first instructions execute the following steps in order. First, while maintaining an interrupt response, initializing variables specified by the new first instructions and not specified by the old first instructions, and not changing variables specified by the old first instructions. Second, after determining there is no interrupt response in process, disabling the interrupt response and proceeding to a third step. Third, initializing a stack, updating an interrupt vector, and updating a function pointer. Fourth, re-enabling the interrupt response.