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delay generation

mr.rohit

Delay generation using timer in pic18f46k22

 

I am using timer interrupt for delay generation in pic18f

when i generate  any delay using timer that time this delay is not proper which i want,it showing some difference in time.

i want knw what is the reason of that difference ?

plz help me...

thank u..

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  • Hello,

    there are too many variables. The more details you add, the more we would be able to help you.

    Basically, I would focus on the following:

    1) oscillator frequency and stability - this is crucial - are you using an integrated RC or some kind of external oscillator? (What are the conditions your design works in? e.g. variable temperature..)

    2) is your timer (and prescaler / postscaler) set correctly?

    3) do you work with the timer properly? (for example if you generate periodically an interrupt, but have poorly written ISR, it looses precision; the same if multiple interrupts occur at once or even worse, the same source of interrupt occurs multiple times, before you finish the ISR)

    4) What makes you think that you have a difference in time delay? Do you have any measurement instrument? What delays are you trying to achieve?

  • in reply to koudelad

    i am  using DSO for time period measurement

    i want time delay in microsecond for CTMU unit in pic18f46k22

    i am using internal oscillator with PLL - 64MHz (16MHz  + 4xPLL),

     

    my timer register detail is

     

     

    T0CONbits.T0PS = 1;                 //timer0 prescalar enable    

        T0CONbits.PSA = 1;

        T0CONbits.T0PS0 = 0;

        T0CONbits.T0PS1 = 0;

        T0CONbits.T0PS2 = 0;

        T0CONbits.T08BIT = 1; //8 BIT MODE

        INTCONbits.TMR0IE = 1; //Enable TIMER0 Interrupt

        T0CONbits.TMR0ON = 1; //Now start the timer!

        T0CONbits.T0CS = 0;

        TMR0 = 254; //load count in TMR0 register

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  • in reply to koudelad

    i am  using DSO for time period measurement

    i want time delay in microsecond for CTMU unit in pic18f46k22

    i am using internal oscillator with PLL - 64MHz (16MHz  + 4xPLL),

     

    my timer register detail is

     

     

    T0CONbits.T0PS = 1;                 //timer0 prescalar enable    

        T0CONbits.PSA = 1;

        T0CONbits.T0PS0 = 0;

        T0CONbits.T0PS1 = 0;

        T0CONbits.T0PS2 = 0;

        T0CONbits.T08BIT = 1; //8 BIT MODE

        INTCONbits.TMR0IE = 1; //Enable TIMER0 Interrupt

        T0CONbits.TMR0ON = 1; //Now start the timer!

        T0CONbits.T0CS = 0;

        TMR0 = 254; //load count in TMR0 register

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