Microcontroller





A microcontroller is a microprocessor optimised to be used to control
electronic equipment (see embedded system). Microcontrollers represent the
vast majority of all computer chips sold, over 50% are "simple" controllers,
and another 20% are more specialized DSP's. While you may have one or two
general-purpose microprocessors in your house (you're using one to read
this), you likely have somewhere between one and two dozen microcontrollers.
They can be found in almost any electrical device, washing machines,
microwave ovens, telephones etc.

A microcontroller includes CPU, memory for the program (ROM), memory for
data (RAM, I/O lines to communicate with peripherals and complementary
resources, all this in a closed chip. A microcontroller differs from a
standalone CPU, because the first one generally is quite easy to make into a
working computer, with a minimum of external support chips. The idea is that
the microcontroller will be placed in the device to control, hooked up to
power and any information it needs, and that's that.

A traditional microprocessor won't allow you to do this, it expects all of
these tasks to be handled by other chips.

For instance, a typical microcontroller will have a built in clock generator
and a small amount of RAM and ROM/EPROM/EEPROM, meaning that to make it
work, all that is needed is some control software and a timing crystal.
Microcontrollers will also usually have a variety of input/output devices,
such as AD converters, timers, UARTs and specialised serial interface buses
like I²C and CAN. Often these integrated devices can be controlled by
specialised processor instructions.

Some modern microcontrollers include a built-in high-level programming
language; BASIC is quite common for this.

Microcontrollers trade speed and flexibility for ease-of-use. There's only
so much room on the chip to include functionality, so for every I/O device
or memory the microcontroller includes, some other circuitry has to be
removed. Finally, it must be mentioned that some microcontroller
architectures are available from many different vendors in so many varieties
that they could rightly belong to a category of their own. Chief among these
are the 8051 and Z80 derivatives.