[ECOS] 2 types of FLASH memory

Andrew Lunn andrew@lunn.ch
Tue Mar 2 08:27:00 GMT 2004


On Mon, Mar 01, 2004 at 02:21:07PM -0000, Radu Cernea wrote:
> Hello,
> 
> Is it possible, with eCcos, to have a FLASH file system that covers 2 
> different FLASH banks?
> 
> I have a board that has 2 different banks of FLASH memory. 
> 
> One consists in 2 AM20LV040B organized as a 16 bit memory:
> -	CYGNUM_FLASH_INTERLEAVE = 2
> -	CYGNUM_FLASH_WIDTH = 8
> -	CYGNUM_FLASH_SERIES = 1
> 
> The 2nd one consists of 4 AM29LV116D) organized as a 32 bit memory:
> -	CYGNUM_FLASH_INTERLEAVE = 2
> -	CYGNUM_FLASH_WIDTH = 16
> -	CYGNUM_FLASH_SERIES = 2
> 
> The design idea was to have the possibility to change the program (stored in 
> the small 2*AM29LV040B which has a socket), and store a large database in the 
> other FLASH bank.

There are two major issues here.

1) There does not appear to be a flash driver for the AM20LV040B. I
   only had a quick look so i might of missed it. If it really does
   not exist you need to write one. This is normally not too
   hard. There are plenty of examples.

2) The current flash infrastructure does not allow two different flash
   drivers to reside in the same eCos configuration. There two
   possible workarounds.

   a) A long time ago, someone, i forgot who, rewrote the flash
      infrastructure it make it more plugable. If i remember
      correctly, that would allow multiple drivers. The contribution
      never got included, but i cannot remember why. Look back in the
      ecos-patches archive.

   b) You might not actually need to be able to driver both flashs at
      the same time. You could build your redboot image to known only
      about the application flash and your application to know only
      about your database flash. You need to asses your requirements
      and see if this is sufficient.

      Andrew

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