Software Protection; Error Protection; Table 20.10 Software Protection - Renesas H8S/2437 Hardware Manual

20.5.2

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 20.10 Software Protection

Item Description
•
Protection by
SCO bit
•
Protection by
FKEY
20.5.3

Error Protection

Error protection is a mechanism for forcibly suspended 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 specified procedures for
programming/erasing. Forcibly suspending 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 FCCS is set to 1 and the error-protection state is entered, and this suspends 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
Error protection is canceled by a reset or in hardware standby mode. Note that the reset should be
released after the reset period of 100 µs which is longer than normal. Since high voltages are
applied during programming/erasing of the flash memory, some voltage may remain after the
error-protection state has been entered. For this reason, it is necessary to reduce the risk of damage
to the flash memory by extending the reset period so that the charge is released.
The program/erase-protected state is entered
by clearing the SCO bit in FCCS to 0 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
Rev. 1.00, 09/03, page 579 of 704