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Section 25 Flash Memory
25.5.2
Software Protection
Software protection is set up in any of two ways: by disabling the downloading of on-chip
programs for programming and erasing and by means of a key code.
Table 25.11 Software Protection
Item
Protection by the
SCO bit
Protection by the
FKEY register
25.5.3
Error Protection
Error protection is a mechanism for aborting programming or erasure when an error occurs, in the
form of the microcomputer entering runaway during programming/erasing of the flash memory or
operations that are not according to the established procedures for programming/erasing. Aborting
programming or erasure in such cases prevents damage to the flash memory due to excessive
programming or erasing.
If the microcomputer malfunctions during programming/erasing of the flash memory, the FLER
bit in the FCCS register is set to 1 and the error-protection state is entered, and this aborts the
programming or erasure.
The FLER bit is set in the following conditions:
1. When an interrupt such as NMI occurs during programming/erasing.
2. When the flash memory is read during programming/erasing (including a vector read or an
instruction fetch).
3. When a SLEEP instruction (including software-standby mode) is executed during
programming/erasing.
Rev. 1.00 Mar. 12, 2008 Page 984 of 1178
REJ09B0403-0100
Description
•
The program/erase-protected state is
entered by clearing the SCO bit in
FCCS which disables the downloading
of the programming/erasing programs.
•
Downloading and
programming/erasing are disabled
unless the required key code is written
in FKEY. Different key codes are used
for downloading and for
programming/erasing.
Function to be Protected
Download
Program/Erase
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