[ECOS] interrupt/virtual vectors confusion

[Matt Sartori]

I'm not sure I understand how this would work. Switching my board into
RAM boot mode means that it maps internal RAM (0x20000000) to
0x00000000. On reset it always start execution from 0x0 but will in this
case find nothing there to execute. On the other hand if booting in the
boards normal mode (USER mode with flash mapped to 0x0) it will boot
fine but when your app wants to change the vector at 0x18 it, as you
pointed out, fail to do so.
Jumping into high address mapping (by that I understand that when an
exception/interrupt occurs all the instructions in the vector at 0x0
jump to another vector in RAM) is what I want to do but still haven't
quite worked out where to do - presumably by changing the vector setup
of Redboot.

m@

-----Original Message-----
From: Andrew Lunn [mailto:andrew@lunn.ch] 
Sent: 16 August 2005 16:21
To: Matt Sartori
Cc: eCos Disuss
Subject: Re: [ECOS] interrupt/virtual vectors confusion

> >You probably need to change this so that it runs in user flash boot
> >mode. If you don't have RAM at 0x0 there is no way to change the
> >vectors. I expect if you run the eCos tests which test interrupts
they
> >will fail.
> >
> 
> And booting in RAM mode Redboot would still work because the first
thing
> it does is copy itself into RAM? My current Redboot setup is running
in
> ROM mode (CYG_HAL_STARTUP == ROM). Presumably that would need changing
> to ROMRAM then?

It should still be able to run in ROM. It just need to take care when
the ROM is remapped out from 0x0 that it is already running from the
mapping at the higher address space. You will find the existing ARM
platforms do this. What is actually quite common is that the reset
vector jumps straight into the high address mapping. 

        Andrew

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