Security Function - NEC V850E/Dx3 Preliminary User's Manual

On-Chip Debug Unit
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28.1.2 Security function

This microcontroller has a N-Wire security function, that demands the user to
input an ID code upon start of the debugger. The ID code is compared to a
predefined ID code, written in advance to the internal flash memory by an
external flash programmer. This function prevents unauthorized persons to
operate the microcontroller in N-Wire debug mode and to read the internal
flash memory area.
The ID code in the internal flash memory can only be written by an external
flash programmer. It can't be changed in self-programming mode and therefore
also not in N-Wire debugging mode.
ID code Be sure to write an ID code when writing a program to the internal flash
memory.
The area of the ID code is 10 bytes wide and in the range of addresses
0000 0070 to 0000 0079
H
The ID code when the memory is erased is shown below.
Address
0000 0079
H
0000 0078
H
0000 0077
H
0000 0076
H
0000 0075
H
0000 0074
H
0000 0073
H
0000 0072
H
0000 0071
H
0000 0070
H
Security bit Bit 7 of address 0000 0079
• Bit 7 of address 0000 0079
0: disabled N-Wire emulator cannot connect to the on-chip debug unit.
1: enabled N-Wire emulator can connect to the on-chip debug unit if the
This security bit can only be modified by programming the flash memory via an
external flash programmer. It is not possible to modify the security bit in self-
programming mode, and therefore also not in N-Wire debugging mode.
After reset the entire ID code area is set to FF
• N-Wire debugging is generally enabled
• the ID code is FF
Consequently controller access is possible without any restriction.
Caution If access via the N-Wire interface should be disabled "block erase disabled"
should be configured as well. Otherwise the flash memory blocks containing
the ID code could be erased and N-Wire access could be enabled.
Preliminary User's Manual U17566EE1V2UM00
.
H
ID code
FF
H
FF
H
FF
H
FF
H
FF
H
FF
H
FF
H
FF
H
FF
H
FF
H
enables or disables use of the N-Wire emulator.
H
H
10-byte ID code input matches the ID code stored in the flash
memory
for all ID code bytes
H
Chapter 28
. This means that
H
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