I don't understand how do you use the IAP in the AT's and P89C's... Are you saying, that even if you execute from external ROM (/EA low) and switch on the bootROM by appropriate SFR flag, jumping to FFF0h jumps to the internal bootROM rather than remaining in the external?

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For documentation on P89V51RD2 FLASH interface registers, go to the SST's website and get the datasheet of their eqivalent of this chip. IIRC there are also examples on how to use the IAP without the provided code in bootFLASH somewhere in the appnotes there.

Of course, as this is not written in Philips'/NXP's datasheet, I give you no guarantee for it (other than "I tried and it works") - but you can also go for the "genuine" SST chips if this is not good enough for you, can't you.

Jan Waclawek