But i have discovered a servere lack of documentation for the chip by Philips
It is quite common (not just Philips) to publish datasheets for '51 derivatives that, in effect, only list differences from the basic '51 as described in "the bible".

Erik

here are the links to "the bible"
Chapter 1
http://www.semiconductors.philips.com/acrobat/v...ARCH_1.pdf

chapter 2
http://www.semiconductors.philips.com/acrobat/v...UIDE_1.pdf


chapter 3
http://www.semiconductors.philips.com/acrobat/v...WARE_1.pdf