Manner of data writing/the read-out in flash memory and the memory storage null which uses flash

摘要

PROBLEM TO BE SOLVED: To prevent information from being lost or becoming a wrong value even when power supply is discontinued while data are updated. SOLUTION: At the time of writing data in a flash memory 1, the magic numbers of blocks 0 and 1 are checked and, when both the magic numbers are proper values, the block having a smaller sequential number is selected by comparing the sequential numbers of the blocks with each other and the data are written by erasing the selected block. Then the value obtained by adding '1' to the sequential number of the other block is written in the sequential number of the selected block and, finally, the magic number is written in the selected block. At the time of reading out data from the memory 1, the magic numbers of the blocks 0 and 1 are checked and, when both the magic numbers are proper, the data are read out from the block having the larger sequential number. When the magic numbers of the blocks are not proper, processing is performed by setting the sequential numbers of the blocks at '0'.