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.
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