Some monthes ago , I was very interested in that field ,I have found many many useful information from net , but unfortunately I have not them with me at present , but there was a software named "Franklin" which was a simulator for 8051 , try to fing in in yahoo search engine . Be sure that there is many information , search for 8051 microcontroller , microcontroller, 89c51 and ...
Cheers
Alan Minasian