Renesas H8S Series Hardware Manual page 798

Section 21 Flash Memory (0.18-µm F-ZTAT Version)
• Flash Key Code Register (FKEY)
FKEY is for software protection that enables download of an on-chip program and
programming/erasing of flash memory. Before setting the SCO bit to 1 to download an on-chip
program or before executing the downloaded programming/erasing program, the key code
must be written, otherwise the processing cannot be executed.
Initial
Bit Bit Name Value
7 K7 0
6 K6 0
5 K5 0
4 K4 0
3 K3 0
2 K2 0
1 K1 0
0 K0 0
Rev. 3.00 Jul. 14, 2005 Page 750 of 986
REJ09B0098-0300
R/W Description
R/W Key Code
R/W Only when H'A5 is written, writing to the SCO bit is valid.
When a value other than H'A5 is written to FKEY, 1
R/W
cannot be set to the SCO bit. Therefore downloading to
R/W
the on-chip RAM cannot be executed. Only when H'5A is
written, programming/erasing can be executed. Even if
R/W
the on-chip programming/erasing program is executed,
R/W
the flash memory cannot be programmed or erased when
R/W
a value other than H'5A is written to FKEY.
R/W
H'A5: Writing to the SCO bit is enabled. (The SCO bit
cannot be set by a value other than H'A5.)
H'5A: Programming/erasing is enabled. (Software
protection state is entered for a value other than
H'5A.)
H'00: Initial value