PWM output pulse variation is not showing in proteus

I want to generate the pulse based on analog input giving to ADC and convert ADC value to PWM signal using LPC2138 ARM processor. I am able to dubug in Keil software in which it works perfectly as I want. but in Proteus it is not working

 #include<LPC214x.h>     // Define LPC2148 Header File

#include <stdio.h>


void initPWM(void);
void fanstart(void);
void Delay();
 #define DONE    0x80000000
 #define START   0x01000000
 #define PRESET  0x00230600
 #define PLOCK 0x00000400
 #define PWMPRESCALE 60   //60 PCLK cycles to increment TC by 1 i.e 1 Micro-second 
 unsigned long Val;
void main ()
{
          initPWM();
VPBDIV   =   0x02;        //pclk @ 30MHz
   //Serial_Init ();
   PINSEL1   =   0x01 << 24; //P0.28 configure as ADC0.1
//   Welcome ();
   AD0CR   =   PRESET | 0x02;
   AD0CR   |=   START;       //Start Conversion NOW

   while (1)
   {
      do

      {
         Val = AD0GDR;
      } while ((Val & DONE) == 0);
      Val = ((AD0GDR >> 8) & 0x0FF);
          if(Val>=0x08)              //check condition of adc input and goto function fan()
           fanstart();
           else
           {
           PWMMR1=0;
               PWMLER =(1<<1);
               }
           Delay();     
   }
}

void Delay ()
{
   unsigned int i,j;
   for (i=0;i<50;i++)
      for (j=0;j<500;j++);
}


void fanstart(void)
{
    //initClocks(); //Initialize CPU and Peripheral Clocks @ 60Mhz


    //IO0DIR = 0x1; This is not needed!
    //Also by default all pins are configured as Inputs after MCU Reset.

               PWMMR1=0;
               PWMLER =(1<<1);
        if( Val>=0x08 && Val<=0x45  ) // Check adc value range and change the pulse width
        {
            PWMMR1 = 1000;
            PWMLER = (1<<1);
        Val=0x00; //Update Latch Enable bit for PWMMR1
        }
        else if(Val>0x45 &&  Val<=0x8B ) // Check adc value range and change the pulse width
        {
            PWMMR1 = 1250;
            PWMLER = (1<<1);    
        Val=0x00;
        }
        else if( Val>0x8B && Val <=0xD1 ) //Check adc value range and change the pulse width
        {
            PWMMR1 = 1500;
            PWMLER = (1<<1); 
        Val=0x00;
        }
        else if( Val>0xD1 && Val <=0xFF) // Check P0.4
        {
            PWMMR1 = 1750;
            PWMLER = (1<<1);
            Val=0x00;
        }


    }
    //return 0; //normally this wont execute ever

void initPWM(void)
{
    /*Assuming that PLL0 has been setup with CCLK = 60Mhz and PCLK also = 60Mhz.*/
    /*This is a per the Setup & Init Sequence given in the tutorial*/

    PINSEL0 = (1<<1); // Select PWM1 output for Pin0.0
    PWMPCR = 0x00; //Select Single Edge PWM - by default its single Edged so this line can be removed
    PWMPR = PWMPRESCALE-1; // 1 micro-second resolution
    PWMMR0 = 20000; // 20ms = 20k us - period duration
   // PWMMR1 = 1000; // 1ms - pulse duration i.e width
    PWMMCR = (1<<1); // Reset PWMTC on PWMMR0 match
    PWMLER = (1<<1) | (1<<0); // update MR0 and MR1
    PWMPCR = (1<<9); // enable PWM output
    PWMTCR = (1<<1) ; //Reset PWM TC & PR

    //Now , the final moment - enable everything
    PWMTCR = (1<<0) | (1<<3); // enable counters and PWM Mode

    //PWM Generation goes active now!!
    //Now you can get the PWM output at Pin P0.0!
}