Datasheet

78K0/Kx2-L CHAPTER 25 FLASH MEMORY
R01UH0028EJ0400 Rev.4.00 707
Sep 27, 2010
25.6 Security Settings
The 78K0/Kx2-L microcontrollers support a security function that prohibits rewriting the user program written to the
internal flash memory, so that the program cannot be changed by an unauthorized person.
The operations shown below can be performed using the Security Set command. The security setting is valid when the
programming mode is set next.
• Disabling batch erase (chip erase)
Execution of the block erase and batch erase (chip erase) commands for entire blocks in the flash memory is
prohibited by this setting during on-board/off-board programming. Once execution of the batch erase (chip erase)
command is prohibited, all of the prohibition settings (including prohibition of batch erase (chip erase)) can no longer
be cancelled.
Caution After the security setting for the batch erase is set, erasure cannot be performed for the device. In
addition, even if a write command is executed, data different from that which has already been
written to the flash memory cannot be written, because the erase command is disabled.
• Disabling block erase
Execution of the block erase command for a specific block in the flash memory is prohibited during on-board/off-board
programming. However, blocks can be erased by means of self programming.
• Disabling write
Execution of the write and block erase commands for entire blocks in the flash memory is prohibited during on-
board/off-board programming. However, blocks can be written by means of self programming.
• Disabling rewriting boot cluster 0
Execution of the block erase command and write command on boot cluster 0 (0000H to 0FFFH) in the flash memory
is prohibited by this setting. Execution of the batch erase (chip erase) command is also prohibited by this setting.
The batch erase (chip erase), block erase, write commands, and rewriting boot cluster 0 are enabled by the default
setting when the flash memory is shipped. Security can be set by on-board/off-board programming and self programming.
Each security setting can be used in combination.
All the security settings are cleared by executing the batch erase (chip erase) command.
Table 25-7 shows the relationship between the erase and write commands when the 78K0/Kx2-L microcontroller
security function is enabled.