[U-Boot-Users] SDRAM Access Question

[VanBaren, Gerald (AGRE)]

> -----Original Message-----
> From: u-boot-users-admin at lists.sourceforge.net
> [mailto:u-boot-users-admin at lists.sourceforge.net]On Behalf Of Jihua
> Cheng
> Sent: Thursday, September 30, 2004 11:24 AM
> To: u-boot-users at lists.sourceforge.net
> Subject: [U-Boot-Users] SDRAM Access Question
>
>
> Hi,
>
> My question about SDRAM may be out of track, forgive me.
>
> I am working on the bring-up of a customer board based on
> PQ2FADS. I use BDI2000. When I use "mm addr value count" cmd
> to write any data( such as, 0x12345678) to any address
> between address 0x0 to 0x7fc, then I use "md" cmd to show the
> contents of address 0x0 to 0x7fc, I found all the contents
> between 0x0 and 0x7fc (2KB range)are the same value (
> 0x12345678), the contents above address 0x800 are not
> changed. If I write a data to any address between address
> 0x800 to 0xc00, the whole block from 0x800 to 0xffc (2KB
> range)are changed, and address 0x0 to address 0x7fc. The My
> BDI2000 configuration file works fine to my PQ2FADS
> evaluation board, and the SDRAM component and design of my
> customer board are copied from PQ2FADS.
>
> I am atruggling for the problem for a quite while. I do not
> know what can cause the 2K range problem? Any point or clue
> are appreciated.
>
> Thanks!
>
> Jihua

Wolfgang Knows.

Then to add to his response...

SDRAM has multiplexed address lines with half of the address lines being presented as a "row" and then the other half as a "column".  SDRAM configuration requires you to configure the SDRAM machine where the row ends and column starts.  If you are wrong, the addressing gets all balled up and you are likely writing and reading into/from an unintended address.

That would be the good news.  The bad news is that, if it isn't a software configuration problem, it is a hardware problem and that would be really bad news indeed (can you spell board spin $$$).

My bet is the SDRAMs you use are different from the SDRAMs used on the PQ2FADS and you didn't reconfigure your SDRAM initialization.  Time to read the SDRAM and 82xx manuals.  You have my sympathy, it takes some time and serious concentration to figure out SDRAM configuration :-/.

gvb


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