Chapter 8 Data Protection And Security; Overview; N-Wire Debug Interface Protection - NEC V850ES/F 3-L Series User Manual

Chapter 8 Data Protection and Security

8.1 Overview

Security functions
Protection
functions

8.2 N-Wire Debug Interface Protection

The microcontroller supports various methods for securing safe
(re-)programming of the internal flash memory and protecting of the flash
memory data against undesired access, such as illegal read-out or illegal
reprogramming.
Security functions provide countermeasures against unexpected failures
during reprogramming processes. These are basically:
• Secure self-programming
• Secure bootloader update
• Boot swapping
• Boot block cluster protection
These functions are described in detail in "Flash Memory" on page 259.
Protection functions provide a set of mechanisms to protect the internal flash
memory data from being read, erased or altered by unauthorized persons.
These are basically:
• On-chip (N-Wire) debug interface protection
• Flash memory erase/write/read protection via the serial programming
interface
Some interfaces offer in general access to the internal flash memory: N-Wire
debug interface, external flash programmer interfaces and self-programming
facilities. All of these interfaces need to be considered for a proper protection
concept.
The following sections give an overview about supported protection methods.
In general read-out of the flash memory contents is possible via the N-Wire
debug interface, but protection against illegal read-out can be enabled. For
protection of the flash memory, the usage of the debug interface can be
protected and it can be disabled. The debug interface is protected via a
10-byte ID code and an internal flag (N-Wire use enable flag).
When the debugger is started, the status of a flag is queried (N-Wire use
enable flag). Set this flag to zero to disable the use of the N-Wire in-circuit
emulator.
When debugging is enabled (N-Wire use enable flag is set), you have to enter
a 10-byte ID code via the debugger. The code is compared with the ID code
stored in the internal flash memory. If the codes do not match, debugging is not
possible.
The N-Wire use enable flag can be set or reset while reprogramming the flash
by an external flash writer or with the self-programming feature. The flag is
located at bit 7 at address 0000 0079
User's Manual U18743EE1V2UM00
.
H
289