LPCXpresso IDE中的主题 Re: Upgrade disaster!

Upgrade disaster!

lpcware — Wed, 15 Jun 2016 22:30:25 GMT

Content originally posted in LPCWare by micrio on Wed Mar 23 09:08:27 MST 2011
[SIZE=4]In my code I provided a backdoor way of defeating the security (CRP) feature. I read a special pin for a zero. If a zero is read, I wait for a few seconds and then issue an IAP command to erase all flash. I have tested this back door in development and it worked OK. I am using CRP3, the highest level of security.[/SIZE]

[SIZE=4]Now we have to upgrade the firmware in a bunch of units. I ground the special pin and expect the code to erase the flash. Well, only about half the units successfully erase thenselves.[/SIZE]

[SIZE=4]The unit emitts pulses during normal operation. When I ground the pin the pulses stop after the safety delay. This is the normal behavior for the backdoor erase feature. However when I power cycle the unit the old code comes back in half the units![/SIZE]

[SIZE=4]I can't predict which units will erase themselves and which won't. They are all the same in both hardware and code.[/SIZE]

[SIZE=4]Am I doing something wrong in my backdoor erase function? Is there a more reliable way to do it?[/SIZE]

[SIZE=4]Thanks,[/SIZE]
[SIZE=4]Pete.[/SIZE]

Re: Upgrade disaster!

lpcware — Wed, 15 Jun 2016 22:30:26 GMT

Content originally posted in LPCWare by larryvc on Wed Mar 23 09:19:06 MST 2011
I'm not sure how pertinent it is but look at this post http://knowledgebase.nxp.com/search.php?searchid=22762

I thought CRP3 was permanent code protection that even ISP could not circumvent. If I'm wrong please let me know.

Re: Upgrade disaster!

lpcware — Wed, 15 Jun 2016 22:30:26 GMT

Content originally posted in LPCWare by micrio on Wed Mar 23 09:41:35 MST 2011
[SIZE=4]It is true that CRP3 cannot be defeated by any external means. It does not prevent reprogramming the flash internally using the IAP function calls. I use the IAP functions to maintain state in my code even with CRP3 set. The only difference is that I am erasing the first page (and all other pages) to kill the CRP3 rather than erasing the last page where my state is saved.[/SIZE]

[SIZE=4]Pete[/SIZE].

Re: Upgrade disaster!

lpcware — Wed, 15 Jun 2016 22:30:27 GMT

Content originally posted in LPCWare by larryvc on Wed Mar 23 09:55:48 MST 2011
Interesting. I'll have to read up on this.

Thanks,
Larry