I programed my own firmware which like the firmware provided by NXP and programed it into P89V51RD2 by Flash Magic.

The firmware of my own provide a entry which P89V51RD2 will jump int0 when it have received command via scom.
Then P89V51RD2 erases code ,program by calling IAP rountine.
And my question is :
when P89V51RD2 execute my own firmware and it need som RAM
which may be have been used by user program. so will they conflict?