[avr-gcc-list] Interrupt Clock

[Dario Carluccio]

Hello AVR-Freaks,

pleas excuse my poor English, but I'll try it anyway, hope you
understand my problem.

I want to program a clock using the internal Timer interrupt.

Therefor i have a Atmel 90C2313 and a 9.216MHz Oszillator
attached to it.


The cntIntClk is declared using this statement:
,-----
| volatile uint8_t cntIntClk;             // 10ms counter for internal clock
`-----

Now I Initialise the Timer1 using this code, to get an
Interrupt every 10ms:

,-----
| // Timer Init code
| TCCR1A = 0;                               // No Output, No PWM
| TCCR1B = (1<<CS11)|(1<<CS10)|(1<<CTC1);   // CK/64 , CTC1
| OCR = 10 * 9216000 / 64000L;              // 10ms: 5A0h = 1440d
| TIMSK = (1<<OCIE1A);                      // Interrupt Enable
`-----

And the Interrupt routine every 10ms is:

,-----
| SIGNAL (SIG_OUTPUT_COMPARE1A){
|   cntIntClk++;        // counter internal clock
| }
`-----

In the Main loop the following code is waiting for hundred 10ms-counts.

,-----
|   // Internal Clock
|   if (cntIntClk>=100){              // every 100 * 10ms
|     cntIntClk -= 100;               // subtract 100 * 10ms from counter
|     InternalClock();                // add 1 second
|     BitSet (CtrlReg, CtrlSecPuls);  // set Flag second
|    }
`-----


The function InternalClock(); adds one second to the internal clock.

But the resulting Time is not sync to the real time, it is a little
bit faster.


Where is my error?


Bye, Dario.

-- 
No SIG