How to set Tmr1 to interrupt every 5 seconds

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  1. #1
    Join Date
    Oct 2008

    Default How to set Tmr1 to interrupt every 5 seconds

    So I'm playing with DT's instant interrupts and even started to modify the T1CON register to adjust the prescaler. I'm using the 16F628A running at 4Mhz so it looks like the maximum time I can get from timer1 is about 0.5s

    4Mhz/4 = 1us * 65535 = 0.0655ms * 8 (max prescaler) = 0.524s and that seems to work as my led blinks around 0.5s ON, 0.5s OFF

    I'm very new to the interrupts and would like to trigger my interrupt if my switch on PortB.0 hasn't been pressed for at least 10 seconds.

    How can I do that?


    @ __config _HS_OSC & _WDT_OFF & _MCLRE_ON & _LVP_OFF & _CP_OFF
    LED1     VAR  PORTB.1
    INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
    INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
    INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
            INT_Handler   TMR1_INT,  _ToggleLED1,   PBP,  yes
        INT_CREATE               ; Creates the interrupt processor
    T1CON = %00110001            ; Prescaler = 8, TMR1ON
    @ INT_ENABLE  TMR1_INT       ; enable Timer 1 interrupts
      PAUSE 1
    GOTO Main
    '---[TMR1 - interrupt handler]--------------------------------------------------
         TOGGLE LED1

  2. #2
    Join Date
    Sep 2005
    Campbell, CA


    One way would be to increase your interrupt rate to once every 50 milliseconds. In your ISR, check for PORTB.0 to be low and increment a counter. If the counter reaches 200, before PORTB.0 goes low, then the button hasn't been pushed for 10 seconds.
    Charles Linquist

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