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Re: ec555 memory map, bootcode


On Thu, Nov 25, 2004 at 09:31:36AM +0100, Meulendijks, J. wrote:
> My board indeed has 2MB RAM and 4MB FLASH so I will be using F04_S02
> configuration. But I am _not_ using the Wuerz bootloader, but a own bootloader.
> So I must set some configuration before starting eCos. Maybe you know exactly
> what things to setup? You already mentioned interrupt vectors and virtual vector
> table.

Compare how a ROM application starts up compared to a RAM
application. The differences your boot loader has to take care off.

What i've done in the past is build my application as a ROM
application but loaded it into RAM via a bootloader. The ROM app then
reinitialises the world to how it expects it, with exception to the
SDRAM controller.  You need to make sure the code which does the SDRAM
initialisation can detect the controller has already been initialized
and leave it alone. If it reinitialises it, its very likely the RAM
becomes unaccessable when it is actually running from RAM and you
crash and burn horribly...

Another option is to make your application a ROMRAM application and
let your application live in FLASH. Your bootloader just jumps into
the application in FLASH. The application then reinitialized to world
to how it wants it and in the process copies itself from ROM into RAM.
Doing it this way you don't need to worry about the SDRAM
controller. Its safe to play around with it since you are running from
ROM not RAM.

        Andrew

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