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timer1 interrupt does not fire

 
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Joined: 24 Mar 2010
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timer1 interrupt does not fire
PostPosted: Thu Dec 23, 2010 3:36 am     Reply with quote
Hi,

I am using pic16f882 with ccs PCM 4.077.

My application goes to sleep after finishes task.

Between sleeps (during the task) I need timer1 to fire an interrupt every ~33ms (see my code).

What happens is that the interrupt fires only once before entering sleep in main loop.

Important note: when I replaced the SLEEP() command with while(1); the interrupt fires correctly and I see a ~33ms pulse as expected.

Can you tell me what is wrong with my code?

Thanks
Code:

#INT_TIMER1
void Timer1_ISR()   
{
    set_timer1(0xFFFF);      //every ~33m sec interrupt and recharge timer
   
   
    if (temporar == 0)
    {
        output_high (no_connected_RA5);    //pulse to measure timer interval
        temporar = 1;
       
    }
    else
    {
        output_low (no_connected_RA5);     //pulse to measure timer interval
        temporar = 0;
       
    }
   
}



void main(void)
{
   BYTE i;
   // set the internal clock to 8MHz ...
   setup_oscillator(OSC_8MHZ);
   setup_timer_1(T1_DIV_BY_1 | T1_INTERNAL);   
   
   INTCON = 0x00; // clear all interrupts
   
   
   set_tris_a(0x00);
   

   port_B_pullups(pin_B0);
   output_float(pin_B0);  //INPUT INT PIN B0
   IOCB = 0x00; // int RB not active
   SETUP_CCP1(CCP_OFF);
   SETUP_CCP2(CCP_OFF);
   SETUP_ADC(ADC_OFF);
   output_low (not_connected_B5);
   output_low (no_connected_RA5);
   output_low (no_connected_RA6);
   output_low (no_connected_RA7);
   

   CLEAR_INTERRUPT(INT_TIMER1);
   
   enable_interrupts (INT_TIMER1);
   enable_interrupts (INT_SSP);
   enable_interrupts (GLOBAL);
     
   #asm  // here interrupt enter !!!   
       NOP  //window for interrupt entry
       NOP  //window for interrupt entry
       NOP  //window for interrupt entry
       NOP  //window for interrupt entry
   #endasm

        disable_interrupts (GLOBAL);

      //--------------------------------
      // enter sleep mode
      //--------------------------------
   
   while(1)
   {
       
       INTCON = 0xD0;             // enable interrupts
       
       TMR1ON = 0;
       SLEEP();                       
   
   
       CLEAR_INTERRUPT(INT_TIMER1);     
       enable_interrupts (INT_TIMER1);
       TMR1ON = 1;
       setup_uart(TRUE);
       
       setup_timer_1(T1_DIV_BY_1 | T1_INTERNAL); 

       INTCON = 0x00;            // disable interrupts

   }
}

_________________
Gil F.
Ttelmah



Joined: 11 Mar 2010
Posts: 19535

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PostPosted: Thu Dec 23, 2010 3:50 am     Reply with quote
Study the data sheet.
Section 14.6.1.
Then the second list of numbered items. Number 1. Note the _limitation_ about Timer1. _Is_ your timer operating as an asynchronous counter?....
(Internal clock _stops_ when you sleep)

Best Wishes
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