problem LPC2148 VIC IRQ request

Hi

the code given below needs to run the ISR when a cpature event occurs.
But on simulating the code and running it on debugger it doesnot switch to irq mode and hence does not go to ISR for that event.

I have tried running the simplest IRQ code given in hitex.pdf.
Even in that case irq ISR is not executed.

can someone please help with this.

Thanks in advance

#include <LPC21xx.H>                       /* LPC21xx definitions */

void T0isr()__irq;


 int main (void) {

        VPBDIV=0x2;
        PINSEL1=0x2000;
         IODIR0=0x0;
         IODIR1=0xff0000;

         T0TCR=0x2;
         T0CCR=0x7;
         T0TCR=0x00;

         VICIntSelect=0x0;
         VICIntEnable=0x10;
         VICVectCntl0=0x24;


          VICVectAddr0=(unsigned long)T0isr;
          T0TCR=0x01;
         while(1);


}

void T0isr()__irq
{
static int value;

        value=T0CR0;
        T0IR=0x1;

         IODIR1 = 0x00FF0000;


      IOSET1 = 0xffff;

        VICVectAddr=0x00;
}