Hi Forum Members,
I am facing a strange problem when using P89C51RD2HBP in IAP(In-Application Programming) Mode.

I use FlashMagic Ver2.01 for programming the CPU. It is working fine. I have written the following code to erase the unused area (0x8000-0xbfff) of Flash Memory (of CPU).
I do not set the Security bits;
After programming through FlashMagic is over, I use the option "Display Flash Memory...", and observe the contents of the unused area 0x8000-0xbfff. It contains 0xff, which is OK.

Then I reset the processor to run the following code in the same board. The following code is just the section of my whole program, so I am posting the concerned area of the code. This routine is called just once and no other IAP calls are made. This code is basically erasing the Flash memory area 0x8000-0xbfff.

I put the processor back into ISP Mode;
Observe the unused area 0x8000-0xbfff. Now it contains something junk at almost 40% of this area.


Section of IAP Code:
Crystal Used is 11.0592 MHz.
/* ******************* */

AUXR1 equ 0a2h
_iap_freq equ 11

...
...
_IAP_EraseUserMemory:
push ie
clr ea
orl AUXR1,#020h


mov r0,_iap_freq
mov r1,#01
mov dph,#080h
mov dpl,#00h
lcall 0fff0h

mov r0,_iap_freq
mov r1,#01
mov dph,#080h
mov dpl,#00h
lcall 0fff0h

anl AUXR1,#0dfh
pop ie
ret

....

Please inform me if I have done any mistake somewhere.

Thanking you,
with best regards from,

Mr. Kiran V. Sutar.



Background Information of requirements of this product:
1. P89C51RD2HBP is preferrable, can try other variants (DIP only).
2. Want to erase the Unused area of the FlashMemory by IAP Only. (No other option.) Because I have to write some information in the Unused area of the flash during Run Time.