AnsweredAssumed Answered

HotSync and backdoor key mechanism

Question asked by Martin Bosma on Apr 9, 2015
Latest reply on Apr 9, 2015 by Tony Papadimitriou

Hi All,


My application has a bootloader and appliation. Recently a new app version was release, which contained a bug.

Programming using the bootloader works ok, but when the application start it seems to crash.

Now it is rebooting in an endless loop and I cannot access the bootloader nor the app, unfortunately.


The application runs on a mc9s08dz60 and I have enabled the backdoor key (NVBACKKEY0-7) and KEYEN=1.

I also found out that I can connect my debugger (Cyclone Pro) in HotSync, using the attach debug session type.


It seems I can connect with my device, but obviously all I read back is 0.

Now, is there any way I can enter the backdoor key so I can step through my code finding the line where the code crashes?

I can access the key registers using the register window and I can also write them with the key I have.

But nothing seems to happen. I've read somewhere that you also need to set KEYEN=1, but the register containing it is readonly.


Any other possibility is also very welcome.