Capabilities of microcontrollers are increasing while their price is decreasing due to technological development. Because of the price factor they are used even in solution of simple tasks, while on the other hand multiple microcontrollers – that perform different functions – can be found in sophisticated systems. These processing units often communicate to each other.
In a typical system – which contains multiple processing units – only one part of these performs significant task from the user point of view, another part is responsible for the system's healthy operation. These processing units with their dedicated hardware and controlling software are called system supervisor units.
A typical example for supervisor unit can be found in personal computers. When the computer is turned off its central processing unit is powered off. However the whole system is not deactivated and some parts of it are still operating. Hence the computer can count date and time when it is turned off, or wake up the system by a key press or a network command.
A supervisor unit is a must when the system consumes high power, its supply is limited, the workload takes only a few percent of time and there are certain jobs to do while it is turned off.
In this thesis the development of the software of a supervisor unit in an embedded system is presented. The WI Drive Next – an accessory to car entertainment systems – contains two microcontrollers. The high power processing unit is responsible for main functionality, and the lower power microcontroller performs the supervising of the system.