RE: mpc555 memory mapping

> I'm wondering if someone can help me with a memory mapping question.
>
> We've got a custom 555 board with 4MB of external RAM, all on one CS.
> When running from internal flash, the base address of the 555 is
> 0x000000 and the external RAM is mapped to address 0x400000. When
> we're debugging, we disable the internal flash and map the external
> RAM to address 0x000000. In this debug configuration, we can't access
> external RAM addresses from 0x2FC000 to 0x3FFFFF because those are
> assigned to internal 555 registers and internal RAM.

Check out the DME bit in the DMBR.  That will allow you to keep your
external RAM configured at 0x400000, and also map the internal flash address
range (at 0x0) on top of it.  Special registers and internal RAM will not be
redirected.

Randall Young
Senior Software Engineer
NavCom Technology, Inc.
A John Deere Company

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