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How is on-chip debug option byte set for program in mass-production?

Latest Updated:07/04/2013

Question:

I am using the RL78 family MCU. From the view of security, such as preventing a third party from tampering with the program, how should the on-chip debug option byte be set for a program to be used in mass-production?

Answer:

The setting of "On-chip debug operation disabled" by the on-chip debug option byte is not sufficient from the point of ensuring security, such as preventing a third party from tampering with the program. The security of the microcontroller has to be set separately.

The operations determined by the combination of the on-chip debugger operation setting by the on-chip debug option byte and security setting of the microcontroller are shown below.

Change the settings appropriately to match the situation in which they are used.

  On-chip debug option byte is set to "Disabling on-chip debugger operation" (*Note 1) On-chip debug option byte is set to "Enabling on-chip debugger operation" (*Note 2)
Microcontroller has a security setting Reading or writing by a third party can be completely prohibited by the security setting of the microcontroller.
  • The code can be read by the on-chip debugger.
  • Erasing or writing to the chip by a programmer can be prohibited.
Microcontroller has no security setting
  • The code cannot be read by the on-chip debugger.
  • The chip can be erased or written to by a programmer. (*Note 3)
  • The code can be read by the on-chip debugger.
  • The chip can be erased or written to by a programmer.

*Note 1
The on-chip debug security ID is to be input when the on-chip debugger is started up. Therefore, as long as "Disabling on-chip debugger operation" is set, the on-chip debug security ID setting is irrelevant.

*Note 2
Since the on-chip debug security ID must be matched to start up the on-chip debugger, a certain level of security can be ensured by setting a unique on-chip debug security ID.

*Note 3
There is a possibility that the on-chip debug option byte or security ID might be rewritten.

Suitable Products
RL78 Family
CS+ (formerly CubeSuite+)
E1 [R0E000010KCE00]
E20 [R0E000200KCT00]