topic Re: Security for QD2/4 with NVBACKKEY in 8-bit Microcontrollers

Security for QD2/4 with NVBACKKEY

Blendi — Fri, 02 Jul 2010 14:50:14 GMT

For production I need secure flash. When in CreateImage.exe is set Secure Device then processor is secured but it is not able re-program again with image where is used EraseModule.? I don´t know why? The CyclonePro stop in security flag.

The image is with commands:

EM ;Erase Module

PM ;Program

PT ;Trim

VM ;verify

SD ;secure

In Metrowerks or in CyclonePro_ProgHcs08.exe is able Erase Module. But why not in Cyclone Image?

Next: When I set NVBACKKEY0-7 for key and KEYEN = 1. Where I can set BACKKEY in programmer for reading code? I can secure but never read? In HC08 was not problem in HCS08 ???

Re: Security for QD2/4 with NVBACKKEY

kef — Fri, 02 Jul 2010 17:47:07 GMT

I'm not familiar with Cyclone and can't say why it can't unsecure flash when ?run standalone?. Maybe because there is no unsecure command. These are questions for P&E.

Regarding backdoor unsecure access, you can't do it via BDM. Backdoor unsecure is possible only executing code on chip. CPU must execute backdoor unsecure sequence, including writing bytes to be compared into NVBACKKEY locations. In secured mode it is not possible to write NVBACKKEY via BDM.

Re: Security for QD2/4 with NVBACKKEY

irob — Wed, 07 Jul 2010 20:38:03 GMT

Blendi, it's my understanding of the HCS08 family security architecture that it can't be unsecured by the programmer (BDM mode) after being programmed with security bits.

The only way to reuse the part is to mass erass with your Cyclone and reprogram.

Why are you wanting to use NVBACKKEY? To read flash contents? Why not just use a serial boot loader or write your own serial interface? That's what I did. Works really well for reading out info about the target and writing out config data to the target.