Micro-controllers are useful to the extent that they communicate with other devices, such as
sensors, motors, switches, keypads, displays, memory and even other micro-controllers.
Many interface methods have been developed over the years to solve the complex problem of
balancing circuit design criteria such as features, cost, size, weight, power consumption,
reliability, availability, manufacturability.
Many microcontroller designs typically mix multiple interfacing methods. In a very simplistic
form, a micro-controller system can be viewed as a system that reads from (monitors) inputs,
performs processing and writes to ( controls ) outputs.
