MCU hangs at Illegal interrupt ISR

Hi

I am using TMS320F28035 picollo controller.

I see that the MCU hangs at the below function in the code.

interrupt void ISR_ILLEGAL(void)   // Illegal operation TRAP
{
  // Insert ISR Code here

  // Next two lines for debug only to halt the processor here
  // Remove after inserting ISR Code
  asm("          ESTOP0");
  for(;;);
}

I observed it in the debug mode.

Can someone please help me on this ?

Thanks & Regards

Smita