I'm using a at91sam9g20 CPU on a project and the hardware we produced did not provide a jumper on the NAND Chip Select the way the EK board is designed. I made slight modifications to the at91bootstrap and for some reason the check for BP4 is not executing allowing me to clear out the boot strap code. I am not unable to connect SAM-BA to flash the device, receiving the typical "No valid processor ID found" message. I know this is due to RomBOOT finding a valid image in the NAND and jumping to it.

Is there any way to force RomBOOT to skip directly to the SAM-BA Boot sequence and not follow the flow diagram in the AT91SAM9G20 Preliminary document (Figure 13-1)?

I think the only thing you can do is short the pull-up resistor on the NAND FLash CE line when you power the unit. I use a metal tweezers to do that that as a quick and dirty way to disable the NAND Flash.

You can provide it a valid bootable device higher up the list. Like an MMC/DataFlash type device.

You can connect via JTAG, reset, halt and step through the code. You could breakpoint it at the boot probing stage, and jump to the SAM-BA entry point instead of going through the list.

You might be able to use/configure something like JFlashARM to manage the NAND via JTAG

I was able to erase the the flash using JLink. For anyone who needs it I did the following.

I created an elf binary that erases NAND Block 0

// eraser_app
int main()
{
hw_init();
nandflash_hw_init();
AT91F_NandEraseBlock0();
return 0;
}

I then started JLink, halted the CPU, loaded my app into memory and ran it.

J-Link> usb 0
J-Link> h
J-Link> loadbin eraser_app.elf 0x20000
J-Link> setpc 0x20000
J-Link> g

Power cycled the board and all I get is RomBOOT. Not the greatest fix, but at least I won't have more dead boards.