[avr-chat] Help! Can't get Timer 3 interrupt to work (mega128)

[Rick Mann]

I have the following code (sorry for the bad formatting; I use 4-char  
tab stops):

void
initControl()
{
        //      Set up Timer 3. It should count, and generate an interrupt at 
TOP.
        //      This will drive the basic control loop.
        
	TCCR3A = (0 << COM3A1) | (0 << COM3A0)									//	Output  
disconnected (we only want interrupts)
				| (0 << COM3B1) | (0 << COM3B0)								//	Output disconnected (we  
only want interrupts)
				| (0 << COM3C1) | (0 << COM3C0)								//	Output disconnected (we  
only want interrupts)
                                | (0 << WGM31) | (0 << WGM30);                  
                                            //      CTC, TOP := ICR3
        
	TCCR3B = (0 << ICNC3) | (0 << ICES3)									//	Disable input  
capture noise canceler, edge select to negative.
                                | (0 << WGM33) | (1 << WGM32)                   
                                            //      CTC, TOP := OCR3A
				| (0 << CS32) | (1 << CS31) | (0 << CS30);					//	prescale: clk(i/ 
o) / 8
        
        OCR3A = 9999;                                                           
                                                        //      100 Hz loop
        //ICR3 = 1999;                                                          
                                                        //      500 Hz loop
        //ICR3 = 999;                                                           
                                                                //      1000 Hz 
loop
        //ICR3 = 499;                                                           
                                                                //      2000 Hz 
loop
        
        TCNT3 = 0;                                                              
                                                                //      Reset 
the timer
	TIMSK |= (1 << OCIE3A);													//	Enable Timer 3 OCRA match  
interrupt
}

It's supposed to call the interrupt handler at 100 Hz. Instead, the  
default handler is getting called at 10 kHz. I've put in handles for  
all of the TIMER3 vectors I could find in iom128.h, but it's still  
triggering something else. Any ideas?

I was hoping to use the timer in CTC mode, with no output pins  
active, to generate an internal interrupt.

Any ideas what I'm doing wrong? I guess my next step is to install  
handlers for all the rest of the vectors...sigh.

Thanks!

--
Rick

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