Is there a non-documented flash read protection in str7?

[dd9]

Posted on April 17, 2006 at 07:01

Is there a non-documented flash read protection in str7?

[dd9]

Posted on April 12, 2006 at 00:58

In coding up and testing a JTAG bootloader for an STR71 (using the DCC Jtag comms channel), and I seem to have accidently activated read out protection on the chip.. It will reprogram correctly and JtAG works fine, but any read attempt either from JTAG or using a ram program yields only FFFF's. The chip does have data programmed at 0x4000000 and runs the program so I know it has data.. ?

All I've read in the Flash programming manual is about write protectiona and the debug protection that disables the JTAG.. Is there any way to re-enable the read access?? I've already cleared and reprogrammed the chip a few times and of course it don't verify, but the program works...

I''m assuming it's another of those undocumented features.. Any help would be appreciated..!

[shangdawei1]

Posted on April 12, 2006 at 01:24

Quote:

On 12-04-2006 at 04:28, Anonymous wrote:

I''m assuming it's another of those undocumented features.. Any help would be appreciated..!

do you mean there is a back door to read the debug protected flash ?

[kim1417]

Posted on April 12, 2006 at 06:38

Did you see it about ''Flash Programming Reference Manual - App Note 11130.pdf''?

I am reading it now.

[dd9]

Posted on April 12, 2006 at 11:00

Yes of course I read the Flash programming manual, and what it describes are how to control the Write protection of the flash and how to activate/deactivate Debug protection (which effectively disables JTAG ).

The issue I have is that the JTAG access to the chip is fine and I can write/erase flash fine, get chip ID, etc, but any direct reads of it (either via jtag or running test code in ram) yields only 0xFFFFFFFF. (I havent tried a test read program from flash yet) I know I can write to it as test programs written to flash work fine. In testing a bootloader I had wrong offsets and tried to flash out of bounds areas of flash space.. I can't see how this would cause this, but yet there it is.. And no, I can't see this as being a backdoor to anything, but seems like very good read protection so far if it's accurate behavior.. I just want the chip back to virgin state (it's on my dev board and I really would hate to have to replace the chip :(

[ This message was edited by: AJT on 12-04-2006 14:33 ]

[dd9]

Posted on April 12, 2006 at 22:32

Well, it seems there are read protection bits afterall.. I used Anglia' ST's nice little gui app IDEAList's (nice job SJO) to clear them and things are cool.. I still havent seen any documentation on those though..