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

[Grant Stockly]

At 09:29 AM 7/25/2002 -0600, you wrote:
> If you're integrating this into a C project, why not use the processor 
> timers to achieve your timing requirements instead of nops and jmps?

I need to have 4 precise 10kHz timers with the same time base and with 
~14bit accuracy.  So I use the 16 bit timer, and on every 10kHz overflow I 
generate an external interrupt to run the secondary timers.

> You could "bookend" the assembly routine: In C, initialize an output 
> compare for the fixed time length, then call or inline your assembly code 
> (minus the additional jmps and nops), then in C, sit in a loop waiting for 
> the output compare to match. The only other caveat is to make sure that 
> the timer output compare is not being used in the mainline code and only 
> used in your ISR.

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

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