1.1 What are microcontrollers and what are they used for?
Like all good things, this powerful component is basically very simple. It is made by mixing tested and high- quality "ingredients" (components) as per following receipt:
The simplest computer processor is used as the "brain" of the future system.
Depending on the taste of the manufacturer, a bit of memory, a few A/D converters, timers, input/output lines etc. are added
All that is placed in some of the standard packages.
A simple software able to control it all and which everyone can easily learn about has been developed.
On the basis of these rules, numerous types of microcontrollers were designed and they quickly became man's invisible companion. Their incredible simplicity and flexibility conquered us a long time ago and if you try to invent something about them, you should know that you are probably late, someone before you has either done it or at least has tried to do it. The following things have had a crucial influence on development and success of the microcontrollers:
Powerful and carefully chosen electronics embedded in the microcontrollers can independetly or via input/output devices (switches, push buttons, sensors, LCD displays, relays etc.), control various processes and devices such as industrial automation, electric current, temperature, engine performance etc.
Very low prices enable them to be embedded in such devices in which, until recent time it was not worthwhile to embed anything. Thanks to that, the world is overwhelmed today with cheap automatic devices and various “smart” appliences.
Prior knowledge is hardly needed for programming. It is sufficient to have a PC (software in use is not demanding at all and is easy to learn) and a simple device (called the programmer) used for “loading” raedy-to-use programs into the microcontroller.
So, if you are infected with a virus called electronics, there is nothing left for you to do but to learn how to use and control its power.
How does the microcontroller operate?
Even though there is a large number of different types of microcontrollers and even more programs created for their use only, all of them have many things in common. Thus, if you learn to handle one of them you will be able to handle them all. A typical scenario on the basis of which it all functions is as follows:
Power supply is turned off and everything is still…the program is loaded into the microcontroller, nothing indicates what is about to come…
Power supply is turned on and everything starts to happen at high speed! The control logic unit keeps everything under control. It disables all other circuits except quartz crystal to operate. While the preparations are in progress, the first milliseconds go by.
Power supply voltage reaches its maximum and oscillator frequency becomes stable. SFRs are being filled with bits reflecting the state of all circuits within the microcontroller. All pins are configured as inputs. The overall electronis starts operation in rhythm with pulse sequence. From now on the time is measured in micro and nanoseconds.
Program Counter is set to zero. Instruction from that address is sent to instruction decoder which recognizes it, after which it is executed with immediate effect.
The value of the Program Counter is incremented by 1 and the whole process is repeated...several million times per second.