[SOLVED] 16 bit timer in avr attiny88

[sammey_geek]

hi,...
i am using a dimmer in my project..for that i want to intialise a 16 bit timer and for every 2.5ms,5ms,7.5ms..it has to generate interrupt....the time period of the clock must 10ms.....can anyone tell me...how to make the timer to generate interrupt at 2.5ms, 5ms, and 7.5 ms....




thank you,

 

[jayanth.devarayanadurga]

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//Timer1 Prescaler = 0; Preload = 10000; Actual Interrupt Time = 2.5 ms
 
//Place/Copy this part in declaration section
void InitTimer1(){
  SREG_I_bit = 1; 
  OCR1AH = 0x27; 
  OCR1AL = 0x10;
  TCCR1A = 0x80;
  TCCR1B |= 0x09; 
  OCIE1A_bit = 1; 
}
 
void Timer1Overflow_ISR() org IVT_ADDR_TIMER1_COMPA {
  //Enter your code here 
}
 
 
 
 
//Timer1 Prescaler = 0; Preload = 20000; Actual Interrupt Time = 5 ms
 
//Place/Copy this part in declaration section
void InitTimer1(){
  SREG_I_bit = 1; 
  OCR1AH = 0x4E; 
  OCR1AL = 0x20;
  TCCR1A = 0x80;
  TCCR1B |= 0x09; 
  OCIE1A_bit = 1; 
}
 
void Timer1Overflow_ISR() org IVT_ADDR_TIMER1_COMPA {
  //Enter your code here 
}
 
 
//Timer1 Prescaler = 0; Preload = 30000; Actual Interrupt Time = 7.5 ms
 
//Place/Copy this part in declaration section
void InitTimer1(){
  SREG_I_bit = 1; 
  OCR1AH = 0x75; 
  OCR1AL = 0x30;
  TCCR1A = 0x80;
  TCCR1B |= 0x09; 
  OCIE1A_bit = 1; 
}
 
void Timer1Overflow_ISR() org IVT_ADDR_TIMER1_COMPA {
  //Enter your code here 
}

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[sammey_geek]

thank you sir,

SREG_I_bit = 1; this is for enabling the global interrupt right?? ......
OCIE1A_bit = 1; it is also sets I bit in SREG ...why we need to enbale it again..if we already enabled global interrupt by SREG_I_bit = 1;


and the values which u have given on comapre register OCR1AH & OCR1AL are the timer count value for required delay??
can u post the formula for calculating timer count value for required delay......

 

[jayanth.devarayanadurga]

See datasheet for registers SREG_I_bit = 1, OCIE1A_bit = 1. I used mikroe Timer Calculator application. Google to get info about how to Calculate Timer values.

 

[sammey_geek]

thank you........