Microcomputer with built-in flash memory, method for writing data to built-in flash memory of microcomputer, and program for writing data to flash memory

This microcomputer with a built-in flash memory includes two memory blocks to be sequentially updated. Each memory block includes block management information and multiple slots for storing data. The block management information includes an update counter indicating a sequence in which the data is updated. Each of the multiple slots has updated data and a write completion flag (WCM) indicating the completion of writing of the updated data. The data in the multiple slots is updated in a predetermined sequence. The microcomputer includes: a memory block detection means for detecting the most recently updated memory block on the basis of the update counters in the two memory blocks (S14); and a slot detection means for detecting, with consideration given to the predetermined sequence and the write completion flags, the slot to which data write is most recently completed in the memory block detected by the memory block detection means (S15-S17).