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

dd9
Associate II
Posted on April 17, 2006 at 07:01

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

5 REPLIES 5
dd9
Associate II
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
Associate II
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
Associate II
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
Associate II
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
Associate II
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..