RTOS Concepts
,What Does Real-Time Mean?
• Main difference to other computation: time
• time means that correctness of system depends
• - not only on logical results
• - but also on the time the results are produced
• real => reaction to external events must occur
during their evolution.
• system time ( internal time ) has to be measured
with same time scale as controlled environment
( external time )
, Foreground/Background.
• Systems which do not use an RTOS
• An application consist of an infinite loop which calls
application modules to perform the desired operations.
• The modules are executed sequentially (background) with
interrupt service routines (ISRs) handling asynchronous
events (foreground).
• Batch process
A process which executes without user interaction.
• Interactive process
A process which requires user interaction while executing
, Kernel
Kernel: the smallest portion of the operating system that provides
task scheduling, dispatching, and intertask communication.
Kernel types
Nanokernel - the dispatcher
Microkernel - a nanokernel with task scheduling
Kernel - a microkernel with intertask synchronization
Executive - a kernel that includes privatized memory blocks, I/O
services, and other complex issues. Most commercial real-time
kernels are in this category.
Operating system - an executive that also provides generalized
user interface, security, file management system, etc
,What Does Real-Time Mean?
• Main difference to other computation: time
• time means that correctness of system depends
• - not only on logical results
• - but also on the time the results are produced
• real => reaction to external events must occur
during their evolution.
• system time ( internal time ) has to be measured
with same time scale as controlled environment
( external time )
, Foreground/Background.
• Systems which do not use an RTOS
• An application consist of an infinite loop which calls
application modules to perform the desired operations.
• The modules are executed sequentially (background) with
interrupt service routines (ISRs) handling asynchronous
events (foreground).
• Batch process
A process which executes without user interaction.
• Interactive process
A process which requires user interaction while executing
, Kernel
Kernel: the smallest portion of the operating system that provides
task scheduling, dispatching, and intertask communication.
Kernel types
Nanokernel - the dispatcher
Microkernel - a nanokernel with task scheduling
Kernel - a microkernel with intertask synchronization
Executive - a kernel that includes privatized memory blocks, I/O
services, and other complex issues. Most commercial real-time
kernels are in this category.
Operating system - an executive that also provides generalized
user interface, security, file management system, etc
