[ECOS] Re: RAM vs. ROMRAM question

Grant Edwards grante@visi.com
Mon Oct 30 13:35:00 GMT 2006


On 2006-10-30, Nick Garnett <nickg@ecoscentric.com> wrote:

> Using a RAM RedBoot to load RAM applications will not work
> since RedBoot would load at exactly the same address as the
> applications, with obvious bad consequences.

That's odd, I do it all the time. ;) I've been shipping
products for years where RedBoot runs from RAM as a "ROM
Monitor" and loads applications into RAM.  All you have to do
is run RedBoot in a section of RAM that you don't use for
applications.

> If this functionality is needed then RedBoot needs to be
> relocated.

Which I guess is what I've done.

> Since the main reason for doing this is often to allow RedBoot
> to be loaded via JTAG,

I usually run RedBoot from RAM because

 1) On my targets, RAM is several orders of magnitude faster
    than ROM, and it allows RedBoot to keep up with network
    traffic better.

 2) Doing things like re-formatting flash and updating RedBoot
    is much simpler if your not runnning from flash.  

I've been talking to our hardware guys about our next desing,
andit might not even have any any executable ROM, so RedBoot
will have to run from RAM.
    
> then targets that support this usually have a JTAG startup
> type to support this. The same startup type supports the
> running of full applications via JTAG too.

I've never heard of a JTAG startup type.  How does it differ
from RAM startup?

-- 
Grant Edwards                   grante             Yow!  Hmmm... A hash-singer
                                  at               and a cross-eyed guy were
                               visi.com            SLEEPING on a deserted
                                                   island, when...


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