MPC850 and GDB help

Wolfgang Denk wd at
Mon Oct 25 09:39:55 EST 2004

In message <77988B3D-260C-11D9-BA35-0050E4B0DC64 at> you wrote:
> Ahh yes.. I wanted to get u-boot loaded into RAM and running from 
> there.  The reason being, I'm having a bit of a hard time writing a 
> flash chip definition file in the MPCBDM Flash.def format for the Intel 
> DA28F320J5 flash chip.  My thought was to boot u-boot from ram and then 
> see if it had better luck at detecting my flash chip and then try to 
> coerce it into writing u-boot to flash for me.

This is the wrong approach. First understand the problem, and fix it.
You will need exavctly this understanding to be able to port U-Boot.

You MUST go step by step. You cannot leapfrog problems.

> As for the "running Linux from ram" thing it was another fleeting 
> thought.  Something along the lines of if I can't get u-boot to run 
> from ram maybe I could get Linux to boot from ram and then go from 
> there.

No, that would even be trying to jump over more than one problem, and
is all the more bound to fail.

> Answer me this if you would.. Does the MPC850 have some sort eeprom or 
> parameter RAM on-chip that would be remembered in the event of a hard 
> reset or power cycle and preclude the chip from booting from flash if 
> certain registers were changed?

No. There is no information kept in the MPC8xx processor itself after
power-cycling it.  But  depending  on  your  hardware  there  may  be
features like an EEPROM with VPD or programmable BCSR's or even plain
old jumpers.

> I'm looking through the manual for the 850 now but don't see anything 
> jumping out at me.

Check the documentation for your _board_. If you have  it,  that  is.
[And  if  you  don't,  then either give up now or plan for a _lot_ of
frustrating experience.]

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at
Boykottiert Microsoft - Kauft Eure Fenster bei OBI!

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