1. An 8-bit microcontroller having extended addressing capability, comprising: an address control special function register capable of being set to one of three address modes, a first address mode being a 16-bit address mode, a second address mode being a 24-bit paged address mode and a third address mode being a 24-bit contiguous address mode; at least one internal memory; and a 24-bit address bus for accessing said at least one internal memory in any of said three address modes.