For the complete documentation read the three "80C51_fam" documents on http://www.semiconductors.philips.com/products/...other.html. This includes the instruction set.

You have to remember that the inputs of an 8051 are digital inputs, so you can only distinguish between "low" and "high" levels. You can find information about input/output functions in the FAQ on this site. In the Code Library are two examples on how to control a standard LCD.

Hope this will help you along. If you have any specific questions, you can always ask here.

Regards,
Rob.