Re: [avr-gcc-list] Hard coded asm in an interrupt routine

[Larry Barello]

GCC pushes all registers used by the ISR in the prolog.  If you have
little C code and no procedure calls, it probably won't save much.
You better check what it saves (compile using the -S option) and add,
in your asm, additional pushes to make some temporary work space.

Better yet: punt C altogether and just save what you need.  There is
*no* reason to use a C declaration if you don't plan on using C code.
Take a look at the source of some of the libraries to see how to write
an ASM module.  It is pretty simple. E.g:
----- Snip here ---
    .func    SomeFunc
    .global SomeFunc
SomeFunc:
    asm
    asm
    asm
    reti
    .endfunc
--- Snip here ----

Cheers!

----- Original Message -----
From: "Grant Stockly" <address@hidden>
...
> My most important question is in an ISR in C, can I use the
temporary
> registers in the AVR for anything that I want?  I don't plan on
having any
> C code in the ISR.  Just a C shell.
>
> Grant
>
> avr-gcc-list at http://avr1.org
>

avr-gcc-list at http://avr1.org