A process program such as an erasing/programming program is stored in a
boot mat in a nonvolatile memory operational in a boot mode specified
after reset start, and a transfer control program for the process program
is also stored therein in advance. With an action of setting control
information to a predetermined register as trigger, the state of an
on-chip CPU is changed from placed in execution of an optional user
program to enabled for execution of a transfer control program in the
boot mat, and the CPU is returned to the re-execution state of the
optional program, after the process program is transferred to an on-chip
RAM.