RE: [ECOS] interrupt/virtual vectors confusion

["Matt Sartori" <msartori at hanoverdisplays dot com>]

>-----Original Message-----
>From: Andrew Lunn [mailto:andrew@lunn.ch] 
>Sent: 16 August 2005 15:25
>To: Matt Sartori
>Cc: ecos-discuss@ecos.sourceware.org
>Subject: Re: [ECOS] interrupt/virtual vectors confusion
>
>On Tue, Aug 16, 2005 at 03:06:39PM +0100, Matt Sartori wrote:
>> 
>> >Is Blinky an eCos RAM program? If so it should of taken over the
>> >interrupt vectors from Redboot. Redboot should no longer be active
>> >unless blinky actually calls into Redboot via the virtual vectors.
>> 
>> Blinky is just a standalone program I decided to use as a test. The
only
>> change I've made to it to make it run is to link it directly into
free
>> ram so that I can run it after having loaded it from Redboot (with a
>> load -r -m ymodem -b 0x20005b68). 
>> The reason I know that Redboot is handling (or at least that Redboot
>> code is being called) the IRQ is that I put while(1){flash an led
every
>> second} at the top of hal_IRQ_handler and that it gets stuck there
when
>> I run Blinky.
>
>Well if you have not taken over the vector it will still be Redboot
>that controls it. If blinky needs to handle the vector simply take it
>over. 
>
>> >The vectors will be in RAM, not ROM. On ARM architectures what
>> >normally happens is that at startup ROM is mapped to address 0x0.
Once
>> >the program is running is remaps the memory so that ROM is moved to
>> >higher addresses and RAM is mapped to address 0x0. The vectors can
>> >then be changed by the application. 
>> 
>> Hmm. I know that my board maps Flash ROM (0x40000000) to 0x00000000.
It
>> also puts something in RAM because when I run Redboot I get the 
>> 	RAM: 0x20000000-0x20010000, [0x20005b68-0x20010000] available 
>> Message. On an interrupt the PC goes to 0x00000018 which is where
>> Redboot's vector sits (having been mapped by the board) and that's
why
>> (I think) the Redboot ends up handling my interrupts. Do you mean
that
>> Redboot also remaps it's vector to 0x20000000? 
>
>The RAM could be mapped into two locations in the address space at the
>same time. You need to read the datasheet for you processor to find
>out what it actually does. 

A quick look at my datasheet mentions that RAM is mapped both to
0x20000000 and 0x00000000, but only in RAM boot mode. I am currently
running in user flash boot mode.

>
>> When you say "the
>> program...remaps the memory" is the program Redboot or your own
program?
>
>eCos ROM application will do this. If the vector was in ROM there
>would be no way for an appliction to register its interupt
>handlers....
>
>RedBoot is just an eCos ROM appliction, so it will of done this. When
>you blinky program gets to run this mapping will still be in force. 
>

The root of my problem.

>Just try overwritting the vector at 0x18 and see what happens. If im
>wrong and it is still in ROM it will either throw on exception and
>drop into the gdb stubs, or the value will not change.

I have tried overwriting the vector at 0x00000018 which is just ignored.
I've not tried changing 0x20000018 if that's what you mean.



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