Some thoughts about the flash device driver and the flashdisk block driver

[Ian Caddy]

Hi Astrid,


Astrid Hanssen wrote:
> 
> Its the Coldfire MCF5208 evaluation board, which contains an AMD
> AM29BDD160G 16/32-bit flash device.
> Although I already started writing my own flash chip driver, now
> I like to switch over to the chip driver format defined by
> flashdisk.h and the example that can be found in libchip/flash.
> After the flash driver will be thoroughly tested, I feel like
> submitting it to libchip/flash.
> 
> However, not the whole area of the flash chip shall be available
> to the libblock flashdisk block driver. The device will also have
> to contain the RTEMS software itself as well as some type of an
> optimized flash parameter storage system.
> The latter may also use the flash device driver, but not the
> flashdisk block driver.

One thing to be aware of is that most NOR type flash chips do not allow 
you to read from them while writing to them.  This would mean that you 
can't run RTEMS from the flash while programming another area of the 
same flash chip.

There are normally two solutions to this problem, copy everything into 
RAM and run from there, allowing full access to the flash, or have a 
separate flash chip for your file system.

Hope this helps.

regards,

Ian Caddy

-- 
Ian Caddy
Goanna Technologies Pty Ltd
+61 8 9444 2634