topic how protec a sector of flash memory in 8-bit Microcontrollers

how protec a sector of flash memory

yecosuma — Sun, 23 May 2010 03:46:21 GMT

hello how i can protec a sector of memory flash?

Re: How to protect a sector of flash memory

peg — Sun, 23 May 2010 05:25:57 GMT

Hello,

Not sure on your definition of a sector, but, you can't just protect a small amount of flash in the middle of the memory map.

FPROT allow a value to be entered where the flash from this address, extended to 16-bits, to the top of flash memory is protected.

Depends to some degree on which device you are using.

See the section of the FLASH chapter of the datasheet that is titled "FLASH Block Protection".

Re: how protec a sector of flash memory

yecosuma — Mon, 24 May 2010 00:39:05 GMT

hello friends;

yes I already read this but i dont understand the procedure,

I have that charger value in FPROT

FPROT=0XDE; FOR PROTECCION OF LAST 8192 BYTES of memory this is correct?

also i must put register NVPROT of this form

const byte NVPROT_INIT @0x0000FFBD = 0XDE; this is correct or not ?

how i can know if the area is protect in the true time simulator of code warrior?

Re: How to protect a sector of flash memory

peg — Mon, 24 May 2010 04:16:41 GMT

Hello,

You programme the value to NVPROT along with the rest of your code.

This value is automatically copied across to FPROT after a reset.

FPROT cannot be written from user code, otherwise it could be unlocked.

FPROT can be written in background debug mode which is how you can "unprotect" the flash.

Using the simulator you could simply check that the value you programmed into NVPROT is automatically copied to NVPROT after reset.

You would need to attempt to programme the flash from user code (resident in RAM) to really confirm that it is indeed protected.

Re: how protec a sector of flash memory

yecosuma — Mon, 24 May 2010 05:07:25 GMT

hello thanks

in my code I put :

const byte NVPROT_INIT @0x0000FFBD = 0XDE; just after of a reset the adress FFBD IS EQUAL 0XDE in the true time simulate

can i am sure that already is protec the flash?

other issue how i can insert a key ? I will must to vrite value in NVBACKKEY in the similar way that NVPROT ?

IT IS CORRECT ?

THANKS NEWLY

Re: How to protect a sector of flash memory

peg — Mon, 24 May 2010 05:42:46 GMT

Hello

I made an error in my last post.

It should have said to check that it is automatically copied across to FPROT (the second time).

As stated before you will need to attempt to alter flash to prove that it is working.

You seem to be confusing flash protection with flash security.

The flash protection we are discussing here is meant to protect against code runaway or the like from inadvertently changing flash contents. It is not meant to protect from someone deliberately doing it.

To unprotect the flash you simply write to FPROT through the BDM connection, not exactly secure but rogue code proof.