Real-Time Operating Systems
Real-Time Operating Systems
Real-Time Operating Systems
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¿ <strong>Real</strong>-time<br />
Introduction (3)<br />
¿ <strong>Time</strong>: main difference to other classes of computation<br />
¿ <strong>Real</strong>: reaction to external events must occur during<br />
their evolution.<br />
¿ System time (internal time) has to be measured<br />
with same time scale as controlled environment<br />
(external time)<br />
¿ <strong>Real</strong> time does not mean fast but predictable<br />
¿ Concept of deadline:<br />
¿ <strong>Time</strong> after which a computation is not just late,<br />
but also wrong<br />
5<br />
¿ Hard RT task:<br />
Hard vs. real time<br />
¿ if missing its deadline may cause catastrophic<br />
consequences on the environment under control<br />
¿ Soft RT task:<br />
¿ if meeting its deadline is desirable (e.g. for performance<br />
reasons) but missing does not cause serious damage<br />
¿ RTOS that is able to handle hard RT tasks is called<br />
hard real-time OS<br />
6<br />
3
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