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Re: 2 types of FLASH memory
- From: Andrew Lunn <andrew at lunn dot ch>
- To: Radu Cernea <rc at unusus dot com>
- Cc: ecos-discuss at ecos dot sourceware dot org
- Date: Tue, 2 Mar 2004 09:27:25 +0100
- Subject: Re: [ECOS] 2 types of FLASH memory
- References: <200403011421.GAA19127@friend.incoop.net>
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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