F28M36P53C2: COntroller goes to Fault ISR

Part Number:F28M36P53C2

Hi,

we program our source code in to two flash sector with segregated 

memory sections without conflict to one and other( one is HI , another N sector).

Now, i am going to erase Flash HI sector using Flash API functions ( mainly .text section )  with external command ,controller going to Fault ISR. ( at that time,we are in Flash N related code space).

How can i trace where it goes to fault ISR or common space between two flash sectors .