8051 Port functions

Ports	Function
Port 0 (Pin 32-39)	Dual-purpose port- 1. general purpose I/O Port.                                 2. multiplexed address & data bus                                                           Open drain outputs
Port 1 (Pin 1-8)	Dedicated I/O port – Used solely  for interfacing to external devices                                                Internal pull-ups
Port 2 (Pin 21-28)	Dual-purpose port-  1. general purpose I/O port.                                   2. a multiplexed address & data bus.                                   Internal pull-ups
Port 3 (Pin 10-17)	Dual-purpose port-  1. general purpose I/O port.                                  2. pins have alternate purpose related to special features of the 8051                                                 Internal pull-ups