Hi all,
I'm agree with Buzzz. An n-bit MCU is simple a MCU with n-bit data bus inside. This is basic knowledge of microprocessor technique.
There are 3 type of signal bus inside a MCU or MPU: data bus, address bus and control bus. 8051, PIC, AVR, 68HC11... have 8bit data bus, so they are called 8bit MCUs. 8086, 80C196 (and many more...) have 16-bit data bus, so they are called 16bit MPUs, MCUs. And so on...
There nothing related to number of ports or number of pins per port here! I/O ports are simple signals that allow CPU exchange data with outside world.
Hope this help.
Kieennx.