Hello I have a problem.

I use a P89V51RD2FA chip from Philips.
I had built an evaluation board with the help of the AN461,to program the P89V51RD2FA with the bootloader in the ISP and IAP mode.
I contact the board and the PC with a serial cable and I use the flashmagic software for programming.

In the last days I wrote a programm and programed the chip with it, and all works.

Now my problem: I want to use the IAP calls to "Program User Code" and "Erase sector".
And there is an advice: "The programming functions are selected by setting up the microcontroller`s registers before making a call to PGM_MTP at 1FF0h".
The sorce code of the IAP functions are in the datasheet of the P89V51RD2FA.

Erase Sector:
Input parameters:

R1 = 08h
DPH = sector address high byte
DPL = sector address low byte

Return parameters:

ACC = 00 = pass
ACC = !00 = fail

Program User Code:
Input parameters:

R1 = 02h
DPH = memory address MSB
DPL = memory address LSB
ACC = byte to program

Return parameters:

ACC = 00 = pass
ACC = !00 = fail

Now my question: What is PGM_MTP?
Is it a special function or only a "Call" to 1FF0h?
Because when I use this call nothing happens in my program.

Can anybody help me to solve this Problem?

O.Hummel