Hi,

We are designing a board based on the AT91SAM920-EK evaluation board. We have some query related to SAM-BA Recovery procedures and the circuitry required for it.

It was mentioned in the document (www.atmel.com/dyn/resources/prod_documents/doc6281.pdf) that if there is a wrong image programmed in NAND Flash or in DataFlash, the board can become non-responsive even to SAM-BA. As a remedy for this erasing data flash or nanad flash was specified as the option. In the development board AT91SAM920-EK the data flash is being erased if pressing the BP4 (PA31 in). My query is, in the new board that we are designing do we need to reserve this pin for the same functionality?

Expecting your valuable reply.

Regards,
Bijesh V.M.

9260 or 9G20?

What provisions are you making for recovery/programming? Do you understand why you would need to do so?

You can do it as a software trap door using any GPIO of your choice and programmed accordingly in AT91BootStrap, or you can use a hardware solution that breaks the CS to the boot strap memory device.

On the 9G20-EK they also had jumpers on the CS lines, as the zero-ohm resistors on the 9260-EK were a pain to remove.

If you haven't already located it, the bootstrap code is here ...
http://www.atmel.com/dyn/products/tools ... ol_id=4093

As CptTitanic mentioned you can use the same GPIO, change it by modifying the bootstrap code or you can implement a hw solution.

I replaced the 0 ohm with a 33 ohm resistor on the NAND Flash and Data Flash CS lines. That way I could short the CS line to 3.3V on power up, using a tweezers. I use 33 ohms to protect the processor pin so it does not get damaged by the 3.3V short. A simple way to disable memory on power up for the few times I have had to do so.

Hi,

We developed board based on "at91sam9g20-ek and in the actual board also we are using same 9g20 processor. We are looking for an optimum method by which we can bring back the sam-ba detection if the samba detection becomes not working due to some wrong boot code in data flash or nand flash.

We are planing to erase data flash (if probelm happens)using the sam-ba once it gets detected.
Storing a recovery program in board or through storage cards seems as an overhead. Also using ICE also will be a problem since in production line or by technician will have to use multiple tools. Sam-ba tool is the one we are planning to use for loading all firmwares. Also we prefer to avoid method of rewiring (mthod of removing chip enable resistors)for the board recovery. But its seems ok to provide input gpios (with some dip switch ) for this recovery procedure. Please correct me if my plan is wrong

I would also like to know were this AT91BootStrap program is stored in the at91sam9g20-ek board? am seing that am able to erase the data flash by pressing one of the push button (BP4) in the at91sam9g20-ek board during the board powerup.

Regards
Bijesh

The AT91BootStrap program is stored in your boot strap device, ie dataflash or NAND. It is copied into SRAM by the internal ROM based ROMBoot program. BMS controls whether external NOR or internal ROM is booted.

You can't get into SAM-BA to erase the dataflash, it's going to start the code stored in the dataflash, which looks at BP4, which erases the front of the dataflash so it is no longer recognized by ROMBoot.

When ROMBoot fails to find a boot strap memory device, it falls into SAM-BA mode.

If your AT91BootStrap code fails, you need to break the CS to the boot strap device, or JTAG, to recover the board.