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configure Timer 2 on P89C51RD2

Moshe Drori

I'll very appreciate if you can help me with the following issue: Configured Timer 2 on P89C51RD2 .

I'm getting around me and become confused from it ...

So, I configure Timer 2 / 16-bit timer (the timer overflows (goes from 0xFFFF to 0x0000)

An interrupt service routine (ISR) have to be invoked whan timer 2 have expired.

(In which register I have to set the interrupt number void timer2_ISR (void) interrupt xx ??)

Can you send me a 'C' example code which demonstrated this issue.

Thanks

Moshe

  • 0

    (In which register I have to set the interrupt number void timer2_ISR (void) interrupt xx ??)
    What do you mean by "In which register", just set the number at "xx"
    What the number is, tou find in the datasheet for your device.

    Erik

  • 0

    Hi,

    Here is an example of using timer 2 from one of my projects, which you can easily customise to suit your own requirements:-

    #define XTAL 22118200L
#define TIMER2_CLOCK_TICK_PERIOD 1e-03 /* 1ms */
#define TIMER2_CLK_TICK_RELOAD (unsigned int)(-TIMER2_CLOCK_TICK_PERIOD * XTAL / 12)

/* init timer2 to required delay and start it*/
static void timer2_init(void)
{
	T2CON = 0x00; /* timer 2 16 bit auto-reload. */
	TL2 = TIMER2_CLK_TICK_RELOAD & 0xFF;
	TH2 = TIMER2_CLK_TICK_RELOAD % 0x0100;
	RCAP2L = TIMER2_CLK_TICK_RELOAD & 0xFF; /* lower byte of 16 bit reload value. */
	RCAP2H = TIMER2_CLK_TICK_RELOAD % 0x0100;/* upper byte of 16 bit reload value. */
	TR2 = 1; /* start timer 2. */
	ET2 = 1; /* enable timer 2 interrupt. */
}

/* timer 2 interrupt function */
static void isr_timer2(void) interrupt 5
{
	TF2 = 0; /* Clear Timer 2 overflow flag bit. Must be cleared in software. */
/* anything else to be done in timer2 interrupt? */
}

    Hope this helps,
    Mark.

  • 0 in reply to Mark H

    Previous Post continued..

    I just realise that there is a mistake on how I have shown the upper byte is calculated to be loaded into TH2 and RCAP2H, they should of been '/' rather than '%' so whe now have :-

    	TH2 = TIMER2_CLK_TICK_RELOAD / 0x0100;
	RCAP2H = TIMER2_CLK_TICK_RELOAD / 0x0100;/* upper byte of 16 bit reload value. */

    I had originally created two macros called HIGH and LOW to give me the upper and lower byte of an unsigned int and in removing them, cut and pasted the wrong lines.

    Mark.

  • 0 in reply to Mark H

    Hi

    Thanks. It's works but u have to add EA=1

    Moshe


    /* init timer2 to required delay and start it*/
    static void timer2_init(void)
    {
    T2CON = 0x00; /* timer 2 16 bit auto-reload. */
    TL2 = TIMER2_CLK_TICK_RELOAD & 0xFF;
    TH2 = TIMER2_CLK_TICK_RELOAD % 0x0100;
    RCAP2L = TIMER2_CLK_TICK_RELOAD & 0xFF; /* lower byte of 16 bit reload value. */
    RCAP2H = TIMER2_CLK_TICK_RELOAD % 0x0100;/* upper byte of 16 bit reload value. */
    TR2 = 1; /* start timer 2. */
    ET2 = 1;

    EA = 1;
    }