Lpc2000

I have a dumb question. I am embarrassed to ask but... I am using a
timer interrupt. My setup is as follows:
	/* Timer 0 interrupt is an IRQ interrupt */
	VICIntSelect &= ~(0x10);
	/* Enable timer 0 interrupt */
	VICIntEnable = (0x10);
	/* Use slot 0 for timer 0 interrupt */
	VICVectCntl0 = 0x24;
	/* Set the address of ISR for slot 0 */
	VICVectAddr0 = (unsigned long)timer0ISR;
	/* Reset timer 0 */
	T0TCR = 0;
	/* Set the timer 0 prescale counter */
	T0PR = 2500;
	/* Set timer 0 match register */
	T0MR0 = 1000;
	/* Generate interrupt and reset counter on match */
	T0MCR = 3;
	/* Start timer 0 */
	T0TCR = 0x01;
	T0IR = 0xFF;

The interrupt was being called, then it stopped. I changed some
settings and it came back, then it stopped again. I added T0IR = 0xFF;
to the end of the setup and it worked, then it stopped again. What
have I missed? I am beginning to feel like a goof.

Thanks,

Mike Haines

---- Original Message ----

From: "mhaines4102" <mhaines4102@...>
To: <lpc2000@yahoogroups.com>
Sent: Thursday, November 10, 2005 9:40 PM
Subject: [lpc2000] Timer Interrupt on Crossworks

> I have a dumb question. I am embarrassed to ask but... I am using a
> timer interrupt. My setup is as follows:
> /* Timer 0 interrupt is an IRQ interrupt */
> VICIntSelect &= ~(0x10);
> /* Enable timer 0 interrupt */
> VICIntEnable = (0x10);
> /* Use slot 0 for timer 0 interrupt */
> VICVectCntl0 = 0x24;
> /* Set the address of ISR for slot 0 */
> VICVectAddr0 = (unsigned long)timer0ISR;
> /* Reset timer 0 */
> T0TCR = 0;
> /* Set the timer 0 prescale counter */
> T0PR = 2500;
> /* Set timer 0 match register */
> T0MR0 = 1000;
> /* Generate interrupt and reset counter on match */
> T0MCR = 3;
> /* Start timer 0 */
> T0TCR = 0x01;
> T0IR = 0xFF;
> 
> The interrupt was being called, then it stopped. I changed some
> settings and it came back, then it stopped again. I added T0IR = 0xFF;
> to the end of the setup and it worked, then it stopped again. What
> have I missed? I am beginning to feel like a goof.

Have you remembered a
   VICVectAddr = 0x00;  /* Clear interrupt flag in the VIC */
and a
   T0IR = 0x01  /* Clear the match 0 interrupt flag */
in your interrupt handler?

Karl Olsen

Well this is what I have now and it is working:
	/* Timer 0 interrupt is an IRQ interrupt */
	VICIntSelect &= ~(0x10);
	/* Enable timer 0 interrupt */
	VICIntEnable = (0x10);
	/* Clear a selected interrupt. 0s should do nothing. */
	VICIntEnClr = 0x0000;
	/* Use slot 0 for timer 0 interrupt */
	VICVectCntl0 = 0x24;
	/* Clear a previous interrupt call */
	VICVectAddr = 0x0;
	/* Set the address of ISR for slot 0 */
	VICVectAddr0 = (unsigned long)timer0ISR;

	/* Reset timer 0 */
	T0TCR = 0;
	/* Set the timer 0 prescale counter */
	T0PR = 2500;
	/* Set timer 0 match register */
	T0MR0 = 1000;
	/* Generate interrupt and reset counter on match */
	T0MCR = 3;
	/* Start timer 0 */
	T0TCR = 0x01;
	T0IR = 0xFF;

I just went through the book and made sure anything that could be
reset, was.

Thanks,

Mike Haines


--- In lpc2000@yahoogroups.com, "Karl Olsen" <kro@p...> wrote:

>
> ---- Original Message ----
> From: "mhaines4102" <mhaines4102@y...>
> To: <lpc2000@yahoogroups.com>
> Sent: Thursday, November 10, 2005 9:40 PM
> Subject: [lpc2000] Timer Interrupt on Crossworks
> 
> > I have a dumb question. I am embarrassed to ask but... I am using a
> > timer interrupt. My setup is as follows:
> > /* Timer 0 interrupt is an IRQ interrupt */
> > VICIntSelect &= ~(0x10);
> > /* Enable timer 0 interrupt */
> > VICIntEnable = (0x10);
> > /* Use slot 0 for timer 0 interrupt */
> > VICVectCntl0 = 0x24;
> > /* Set the address of ISR for slot 0 */
> > VICVectAddr0 = (unsigned long)timer0ISR;
> > /* Reset timer 0 */
> > T0TCR = 0;
> > /* Set the timer 0 prescale counter */
> > T0PR = 2500;
> > /* Set timer 0 match register */
> > T0MR0 = 1000;
> > /* Generate interrupt and reset counter on match */
> > T0MCR = 3;
> > /* Start timer 0 */
> > T0TCR = 0x01;
> > T0IR = 0xFF;
> > 
> > The interrupt was being called, then it stopped. I changed some
> > settings and it came back, then it stopped again. I added T0IR = 0xFF;
> > to the end of the setup and it worked, then it stopped again. What
> > have I missed? I am beginning to feel like a goof.
> 
> Have you remembered a
>    VICVectAddr = 0x00;  /* Clear interrupt flag in the VIC */
> and a
>    T0IR = 0x01  /* Clear the match 0 interrupt flag */
> in your interrupt handler?
> 
> Karl Olsen
>

--- In lpc2000@yahoogroups.com, "mhaines4102" <mhaines4102@y...> 
wrote:
>
> I have a dumb question. I am embarrassed to ask but... I am using a
> timer interrupt. My setup is as follows:
> 	/* Timer 0 interrupt is an IRQ interrupt */
> 	VICIntSelect &= ~(0x10);
> 	/* Enable timer 0 interrupt */
> 	VICIntEnable = (0x10);
> 	/* Use slot 0 for timer 0 interrupt */
> 	VICVectCntl0 = 0x24;
> 	/* Set the address of ISR for slot 0 */
> 	VICVectAddr0 = (unsigned long)timer0ISR;
> 	/* Reset timer 0 */
> 	T0TCR = 0;
> 	/* Set the timer 0 prescale counter */
> 	T0PR = 2500;
> 	/* Set timer 0 match register */
> 	T0MR0 = 1000;
> 	/* Generate interrupt and reset counter on match */
> 	T0MCR = 3;
> 	/* Start timer 0 */
> 	T0TCR = 0x01;
> 	T0IR = 0xFF;
> 
> The interrupt was being called, then it stopped. I changed some
> settings and it came back, then it stopped again. I added T0IR = 
0xFF;
> to the end of the setup and it worked, then it stopped again. What
> have I missed? I am beginning to feel like a goof.
> 
> Thanks,
> 
> Mike Haines
>

I have Timer0 interrupt 2000 times per second using a prescale of 2 
and a count of 14400.  Besides toggling an LED, it increments a tick 
counter for the uIP (TCP/IP) stack - specifically for telnet.

Here is my Timer0 setup (setup.c):

// set up Timer 0
TIMER0_TC    = 0; // clear the timer count
TIMER0_PR    = 1; // prescale divide by 2
TIMER0_MR0   = 14400; // divide by 14400 to get 2048 ints per second
TIMER0_MCR   = 0x03; // interrupt on match, reset on match
TIMER0_TCR   = 0x01; // start the timer
VICVectCntl3 = 0x00000024; // set priority 3 for Timer 0
VICVectAddr3 = (unsigned long) T0ISR; // pass the address of the ISR
VICIntEnable = 0x00000010; // enable interrupt

This is my interrupt routine (interrupt.c):

void T0ISR(void)
{
 ticks++;
 if ((ticks & 0x07FF) == 0) // every 2048 ticks
 {
 if (ticks & 0x0800) // every 4096 ticks
 IOSET = LED_YELLOW;
 else
 IOCLR = LED_YELLOW;
 }
 TIMER0_IR = 0x01;
 VICVectAddr = 0xFF;
}

Here is my interrupt routine prototype (interrupt.h):

void T0ISR (void)   __attribute__ ((interrupt));
	

The only other changes I have made is to increase all of the stacks 
to 64 bytes from 4.  Not necessary perhaps, but safe.

Richard