I have, in the past, often referred to the Philips revised version of the old Intel MCS 51 Microcontroller Family User's Manual available on-line. Philips has decided to destroy their website and make it virtually impossible to find anything, however looking for something else I found the 80C512FAM.. documents again. They are now at http://www.semiconductors.philips.com/products/...other.html

If everything else fails, read the manual.

Erik