ARM and interrupts

[Bill Gatliff]

Toralf:


> How about the stack pointer etc.? Do I have to set up that 
> specifically for IRQ mode, too? Is the morale perhaps that I simply 
> can't use the crt0 provided with newlib? (I was otherwise thinking 
> that I might simply insert the vectors in front of it, if you now what 
> I mean.) 


It depends.  Angel, when present, sets up the stack pointers for all 
operational modes.  If you turn of RDP/RDI, you expose a bug whereby the 
stack pointer gets initialized to a value that causes it to gobble up 
your program!

You're mostly correct: for embedded work you'll need to roll your own 
_start function.  Use the crt0 that comes with newlib as a guide, but 
note that it doesn't do anything involving the various stack pointers 
for the "other" modes.  See gdbstubs for that if you need examples.

>> See also the ARM Architecture Reference Manual, by David Seal. It 
>> contains some brief examples too.
>
>
> I'll have a closer look at what you mention here... 


The book is good, but it isn't cheap.  But hey, lack of knowledge on 
these details is even more expensive!

> We also found some example code for a test board from Motorola (we're 
> actually using a Motorola CPU with ARM core), and it turns out that 
> they also have an "Interrupt Controler" application note that's quite 
> helpful (unlike the CPU reference manual, I might add..) 


Yes, I was going to mention something related to that.  With the 
"advanced/vectored interrupt controllers" that are all the rage now, 
there are some nifty tricks you can use to really boost interrupt 
handling performance.  I have examples, but if there are some in your 
manuals then go with them.


b.g.

-- 
Bill Gatliff
bgat@billgatliff.com



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