The I/O core can contain up to 16 different modules where you can plug in different hardware modules to interface with the Whizz80 computer. The design of the I/O core places the addressing and decoding of ports the responsibility of the the core. This means that the slot you plug your I/O module into determines the port addresses and as a result makes each module an isolated unit.
Some examples of some I/O modules are
The I/O core concept design has heavily influenced by this webpage. I have borrowed many of the ideas from there and have adapted them into the Whizz80 system.