Lpc2000

--- In lpc2000@yahoogroups.com, "ylavoie66" <ylavoie66@...> wrote:

> Is it something you already tried and tested? 
> Philips documentation does not clearly state that.  Then again it 
> won't be the first time an IC manufacturer gives incomplete 
> documentation :(
> 
> Regards,
> 
> Yves Lavoie
>

Yves,

The following code generates a 1ms "tick" interrupt, which I believe is 
what you're looking for. It assumes a 60 MHz system. The manual is 
quite clear about the need to subtract one from the desired value when 
setting the counter value.

Hope this helps: it's been tried an tested on a LPC2134 (pretty much 
the same as the LPC2138). Note that the function to initialise the 
timer is called once on system startup, and assumes (all) interrupts 
are disabled.

Brendan

>>>>>>>>>>>>>> CODE EXAMPLE <<<<<<<<<<<<<<<<<<<<

/* TIMER counter value for 1ms tick */

#define	TIMER_TICK_1_MS   (59999)   /* VPB at 60 MHz clock */

/* system tick count in milliseconds */

static volatile
int   tick_count;

/*
 * Interrupt handler for 1ms "tick"
 *
 * The handler will be called from interrupt processing context
 */

static
void    tick_isr(void)

{
    /* reset the interrupt */

    REG(TIMER1_IR) = 0x01;

    /* bump the millisecond conter */

    tick_count++;

    /* call RTOS to handle tick */

    RtosTick();

    return;
}

/*
 * Start "tick" interupt for 1ms system "tick" using TIMER 1
 */

static
void    tick_init(void)

{
    /* ensure timer 1 is off */

    TIMER1_TCR = 0x00;

    /* set timer counter and prescale counter */

    TIMER1_TC = 0x0;
    TIMER1_PC = 0x0;

    /* set prescale and match values to give 1 ms "tick" */

    TIMER1_PR = 0x0;
    TIMER1_MR0 = TIMER_TICK_1_MS;

    /* set control to interrupt on MR0 match, 
       and reset to 0 (i.e. "tick") */

    TIMER1_MCR = 0x3;

    /* vector TIMER 1 as mid-level priority and enabled */

    VICVectCntl11 = 0x25;

    /* vector TIMER 1 interrupt address */

    VICVectAddr11 = (unsigned int) tick_isr;

    /* enable TIMER 1 in VIC */

    VICIntEnable = 0x0020;

    /* go start timer 1... */

    TIMER1_TCR = 0x1;

    return;
}

>>>>>>>>>>>>>> END CODE EXAMPLE <<<<<<<<<<<<<<<<<<<<