The configuration of a microcomputer to be used as the control device of a medium
reading apparatus is such that writing unit by unit into and erasion block by block
from a prescribed area, such as a user data storage area, in a nonvolatile memory
built into the microcomputer makes possible, if any writing into the user data
storage area is needed, for data to be successively written while updating the
units, data included in the prescribed area to be erased when all the units have
been written into, and the next data to be written into the erased blocks.
