Subject: Re: SDRAM is finally working

From: "Donald White" <[email-masked]>
Date: Wed, 20 Feb 2002 17:41:27 -0700

Navin,

While I have no right to ask, could you provide a tutorial on how one
goes from the SDRAM chip specifications to the UPM words?

I did a port of HHL 2.0 to an 860 board and never felt I really
understood the SDRAM initialization.  The board manufacturer provided a
set of UPM words.  These had been used by a previous vxWorks port.  But
burst mode never worked right for either and I was never confident that
the UPM words were right.

Thanks,

Don

Navin Boppuri wrote:
>
> I now have Linux kernel booting up and mounting a file system without
>any problems. I had all the timing right but my SDRAM initialization
>was messed up. My init sequence was missing a single NOP command at
>the very start. And so, things worked fine with PPCBOOT but with more
>memory intensive stuff that the kernel does, I had software emulation
>errors during the kernel boot.
>
> I appreciate all the help from Wolfgang in doing this. I got my very
>first SDRAM interface working on the 855 processor.
>
> I would like to point out to everyone in this mailing list that there
>is an App. Note from Motorola (ANxxx/D) that talks about a high speed
>SDRAM interface to the MPC823. The document is a good start for anyone
>trying to interface the 8xx processor to and SDRAM while running the
>bus at speeds greater than 50Mhz. But please NOTE that the timings
>shown in the example SDRAM interface in this App. Note for the Micron
>MT48LC* chip are very wrong. Please do not design your timing around
>this example.
>
> I looked at the sample timings from various board supports in PPCBOOT
>(eg. hermes). I manually inserted these timings into an *.mgp file for
>the MCUinit utility and looked at them in the GUI interface. But the
>final timings are totally dependent on your particular SDRAM chip ( The
>fact which Wolfgang tells us about all the time ;) ).

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