Subject : Microcontroller and Embedded Programming

Topic : Embedded/Real Time Operating System

Difficulty : Medium

RTOS(Real Time Operating System):

The embedded s/w consists of the operating system and the applications. The operating system used in the most of the cases is RTOS (Real Time Operating System).

RTOS has two terms i.e “real time” and “operating system”. The term real time refers to the events with deadlines i.e whenever an event occurs, there is deadline for the event to be serviced and the event should be serviced before deadline. The operating system refers to basic functions of OS that it has to perform scheduling, synchronization, multitasking, and memory management, inter task communication etc.

There are two types of RTOS:

1) Hard RTOS 2) Soft RTOS

1. Hard RTOS - The hard real time system is required to complete the critical task within guaranteed amount of time. Every process is submitted along with the time in which the task must be completed. The scheduler does the following operations: The first is allowing process, guaranteeing that the process will be completed on time. The second is that rejection of process i.e. resource reservation. In this case it is required that scheduler knows the exact length of time each type of process that the operating system has to perform. Example: Space shuttle of NASA.

2. Soft RTOS : Soft real time system on the other hand are less restrictive by nature. A soft real time system requires that the critical processes receive priority over less critical ones. Example: Multimedia devices, Graphic devices, home appliances.