PIT interrupts

Dear members

I am trying to run the PIT interrupt. I have taken the example of the 
sci interrupt in AN2109( example 7.3.4 ISR using C only-One interrupt 
source) Instead of using SCI i am using a PIT interrupt. I have taken 
the PIT initialization routine from PIT FROM EXAMPLE 7.3.1 IN an 
2109). When I created a new project The linker command file generated 
automatically. I want to know whether we should use the debug version 
or the auto flash version for executing the ISR. I tried to use the 
debug version. the problem is when i run the program the PIT counter 
is decrementing and when it reaches 0 it sets the PS bit, Sipend 
Register, Sivec register. But after that it is executing without 
returning to the main program. When i tried to find if there a code 
in 0x500 i couldn't find any code there. should i change the lcf file.
I am getting a warning that says can't find irqsection in lcf file. 

Ii would appreciate if you can answer these question. i have attached 
the main program and lcf file for your reference. should i change any 
of thse files to make my program work or should i set any jumpers or 
switches.
	
#include "mpc555.h"
#include <iostream>
#include<math.h> 
using namespace std;

void init_555();
void init_mios();
void initPIT();

UINT32 loopctr = 0 ;

    int flag1 = 0;
    int pitctra1,countera1;
unsigned long x1[2],y1[2],z1[2],a1[2],b1[2],c1[2],m1[2],n1[2],c2[2];  
	int i=0;
	int j=0;
	double z2[2],z3[2],d1[2],p1[2],p2[2];



	#pragma push
	#pragma section code_type".text" code_mode=far_abs
	void PIT_Int(void);
	#pragma section code_type ".IrqSect"
	void Ext_Isr();
	#pragma pop


void init_555()
{
	USIU.SYPCR.R = 0xffffff03;		
	USIU.PLPRCR.B.MF = 0x009;	
      //while(USIU.PLPRCR.B.SPLS==0)
	UIMB.UMCR.B.HSPEED = 0;			
}

void init_mios()
{
 							
	MIOS1.MCPSMSCR.B.PSL = 0x4;		
	MIOS1.MCPSMSCR.B.PREN = 1;		
 								
	MIOS1.MPWMSM2SCR.B.CP = 0xf6;	
	MIOS1.MPWMSM2PERR.R = 2000;		
	MIOS1.MPWMSM2PULR.R = 500;		        
MIOS1.MPWMSM2SCR.B.EN = 1;
		}



void initPIT()
{					
	USIU.PITC.B.PITC = 0x1000;
	USIU.PISCR.B.PITF = 0;		
        USIU.PISCR.B.PTE  = 1;					
	USIU.PISCR.B.PIRQ = 0x80;		
	USIU.PISCR.B.PIE = 1; 		
	USIU.SIMASK.R = 0x40000000;	
}
   
   
 

void main()

{
	init_555();			
	init_mios();		
	initPIT();					
	asm(" mtspr EIE, r0");		
	while (1==1) {
		loopctr++;
	 if(flag1==1)
	 {
	 	  
   // The code below is used to measure the period and frequency of 
pwm signal.
// I have taken reference from the Motorola AN1778.pdf(Programming 
the MDASM)	
   	MIOS1.MMCSM6SCR.R = 0x0eff;  /* Set clock prescalerto follow 
MMCSM with a prescaler
	                             division of 1. This means 
counter runs at 100ns per count*/
	MIOS1.MMCSM6MLR.R = 0x0000; /*Resetting counter to ensure it 
starts properly */
	MIOS1.MDASM11SCR.R =0x0002; /* Used to initialize MDASM 
channel */
    
    while(j<2)
  {
    x1[0] = MIOS1.MDASM11AR.R; /* Using an array to store the two 
consecutive rising edges*/
   	y1[0] = MIOS1.MDASM11BR.R;
    if(x1[0]> y1[0])
   {
   	z1[0]=x1[0]-y1[0];
    z2[0] = ((z1[0] * 100 )* pow(10.0,(-6.0)));
    z3[0] = 1/(z2[0] * pow(10.0,(-3.0)));
	cout<<"\nThe time period of pwm signal is:"<<z2[0]
<<"ms\r"<<endl;
	cout<<"\nThe frequency of pwm signal is :"<<z3[0]
<<"Hz\r"<<endl;
	j++;
   }
   else 
   {
   m1[0]=65535-y1[0];
   n1[0]=x1[0]+m1[0];
   p1[0]= ((n1[0]*100)*pow(10.0,(-6.0)));
   p2[0]= 1/(p1[0]*pow(10.0,(-3.0)));
   cout<<"\nThe time period of pwm signal is:"<<p1[0]<<"ms\r"<<endl;
   cout<<"\nThe frequency of pwm signal is :"<<p2[0]<<"Hz\r"<<endl;
   j++; 
   
   }
  }
  // The code below is used to measure on time of pwm signal
  	MIOS1.MMCSM6SCR.R = 0x0eff;  /* Set clock prescalerto follow 
MMCSM with a prescaler
	                              division of 1. This means 
counter runs at 100ns per count*/
	MIOS1.MMCSM6MLR.R = 0x0000; /*Resetting counter to ensure it 
starts properly */
	MIOS1.MDASM11SCR.R =0x0001; /* Used to initialize MDASM 
channel */
	while(i<2)
 {
    a1[0] = MIOS1.MDASM11AR.R; /* Using an array to store rising and 
falling edges*/
    b1[0] = MIOS1.MDASM11BR.R;
    if(a1[0]> b1[0])
   {
   	c1[0] = a1[0]-b1[0];
    d1[0] = ((c1[0] * 100 )* pow(10.0,(-6.0)));
   	cout<<"\nThe time period from falling to rising edge is:"<<d1
[0]<<"ms\r"<<endl;
	cout<<"\nThe On time of pwm signal is:"<<z2[0] - d1[0]
<<"ms\r"<<endl;
	i++;
   } 
   else 
  {
  c1[0]=65535-b1[0];
  c2[0] = a1[0]+c1[0];
  d1[0] = ((c2[0] * 100 )* pow(10.0,(-6.0)));
  cout<<"\nThe time period from falling to rising edge is:"<<d1[0]
<<"ms\r"<<endl;
  cout<<"\nThe On time of pwm signal is:"<<z2[0] - d1[0]
<<"ms\r"<<endl;
  i++; 
  }
}
flag1=0;
}
}
}


#pragma interrupt SRR on 

void Ext_Isr()
{

#define LEVEL0 0x40000000
asm (" mtspr EID, r0 "); // Set MSR.RI - now recoverable
if (USIU.SIPEND.R&LEVEL0) // Check if IRQ is level 0
{
PIT_Int(); // Call PIT C interrupt handler
}
else
{
// Just return
}
asm (" mtspr NRI, r0 "); // Clear MSR.RI - now irrecoverable

};
#pragma interrupt off


 void PIT_Int()
{
if(USIU.PISCR.B.PS == 1)
 {
     pitctra1++;					// Increment 
PIT interrupt counter
     if(pitctra1==100)	
     {
     countera1 = countera1+100;
     MIOS1.MPWMSM2PULR.R = 100;		/* Set Duty Cycle to 25%*/
     MIOS1.MPWMSM2SCR.B.EN = 1;		/* Enable output on PWM2 */
	 USIU.PISCR.B.PS = 1;	    // Negate interrupt request
     flag1=1;	
	 pitctra1 = 0;
     }
     else
     {
     	
     }
 }
else
 {
    	
 }
}

LINKER COMMAND FILE

_flash_source	= 0x00c10000;		// **NOTE: MUST match RAM 
buffer address
								
	// setting in linker preference panel

/* Default linker command file for 555 ETAS board */

MEMORY {
	ram : org = 0x00c02000
	rom : org = 0x00000000 // desired ROM address (boot address 
for 555)
}
 
/* We use FORCEFILES so that the linker will not deadstrip the file 
reset.s. The function
	reset would be deadstripped since it is not ever called by 
anything */

FORCEACTIVE { gInterruptVectorTable, __reset }

SECTIONS {

	.reset : {} > rom
	.init  : {} > rom
		
	GROUP : {
		.text (TEXT) ALIGN(0x1000) : {}
		.rodata (CONST) : {
			*(.rdata)
			*(.rodata)
		}
		.ctors : {}
		.dtors : {}
		extab : {}
		extabindex : {}
	} > rom 	// for ROM images, this can be 'rom' if you 
want to execute in ROM
				// or 'code' if you want to execute 
in RAM
	GROUP : {
		.data : {}
		.sdata : {}
		.sbss : {}
		.sdata2 : {}
		.sbss2 : {}
		.bss : {}
		.PPC.EMB.sdata0 : {} 
		.PPC.EMB.sbss0 : {}		
	} > ram

	// The dummy section is just a placeholder.  The linker 
automatically
	// generates an address for it in the ROM image, which tells 
us
	// where the end of the ROM image is.

	.dummy ALIGN(64): {}
	
	_flash_dest = _f_reset;			// true flash address 
starts w/.init section
	_flash_size = _f_dummy_rom - _flash_dest;

	// The .fcopy section contains a small piece of code that 
copies the
	// ROM image to flash.  We don't copy the .fcopy section 
itself to flash
	// because it could erase the flash if it were accidentally 
executed
	// at a later time.
	//
	// Bind it to the address it will occupy in the RAM buffer so 
we can
	// execute it directly from the RAM buffer.

	.fcopy BIND(_flash_source + _flash_size) ALIGN(64) : {
		*(.fcopy)
	}

	.fcopy_data : {} 

	// The internal flash algorithms provided by Motorola are
	// packaged in a binary file.  The linker includes the 
contents
	// in the .BINARY section.
	.BINARY : {}
}






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