PIC Training & Development System

What is a Microcontroller?

At the heart of your PC is a microprocessor which we can think of as being its brains; the means by which it thinks. It has the power to think in that it knows how to perform simple tasks such as moving data, simple arithmetic and not much more. If we want it to perform any other tasks we must explain in minute detail how they are to be processed. This list of instructions is called a programme and needs somewhere to be stored.

In a PC there are three types of memory, permanent ROM memory which is programmed by the manufacture to contain the low level operating system, programme RAM memory to store programmes loaded by the user, and data RAM memory to store variables while the programme is running. In a PC the second two are taken from the same pool of memory.

The microprocessor as well as needing the three types of memory also needs a regular input pulse to govern its rate of processing the instructions. We call this the clock or oscillator.

PIC16F84 microcontroller shown 4 times actual size

To understand what a microcontroller is imagine the microprocessor, the three types of memory and the oscillator circuits being incorporated into a single chip. That in simple terms is a microcontroller.

So you immediately ask 'Why then does a PC need to have separate memory and oscillator circuits?', and you have the key to understanding the difference between the chips we call a microprocessor and the chips we call a microcontroller. The memory and oscillator circuits can only be incorporated into the chip by accepting various compromises. When compared to a PC a microcontroller contains a relatively simple microprocessor and a tiny amount of memory, but by having all the memory inside the chip the connections that were needed to manipulate this as an external component are freed to be used for any other purpose. So a microcontroller has a large number of spare input/output lines which we can use to control our own circuits.

A microcontroller is a complete (simple) computer without the power supply, the keyboard or the monitor.

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