Real Time Operating System In this section we briefly survey the important features of some of the popular real time operating system that are being used in commercial application. There are 9 popular real time operating system available in the depends upon the work. 1. pSOS (Portable Software On Silicon) : Name of the RTS : Portable Software On Silicon (pSOS) Application: PSOS based application development has schematically been shown in fig 1. the host computer is typically a desktop that supports both Unix & windows host. The target board contain the embedded processor, ROM, RAM etc. The host computer runs the editor, cross compiler, source level debugger and library routines. Psos+ and other optional modules such as PAN+,PHILE and PROBE are instell on a RAM on the terget board. PAN+ is the network manager thats thats provides TCP/IP communication between the host abd the terget over ethernet and FDDI. It conforms to unix 4.3 socket syntex and is compatible with other TCP/IP based networking standerds search as ftp and NFS. PROBE+ is a terget debugger and XRAY+ is the Source level debugger. XRAY+ invokes PROBE+ to provide a seamless debugging enviroment to real time application developer. The application development is done on the host machine and download to the terget board. The application is debugged using the source debugger(XRAY+). During application development the application on to a RAM on the target. Once the application runs satisfactorily, it is fused on the ROM. Develop by: pSOS (Portable Software On Silicon) is a realtime operating system (RTOS), created in about 1982 by Alfred Chao, and developed/marketed for the first part of its life by his company Software component group (SCG). In the 1980s pSOS rapidly became the RTOS of choice for all embedded systems based on the family architecture. Scheduling Algorithm: Static table driven: The feasibility and schedule are determined statically. A common example is the cyclic executive, which is also used in many large-scale dynamic real-time systems. It assigns tasks to Editor Cross compiler XRAY+ Libraries Terget Board ROM APP PSOS+ PHILE PROBE
It is a short information about how many real time operating system present in now a days.
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Real Time Operating System
In this section we briefly survey the important features of some of the popular real time operating
system that are being used in commercial application.
There are 9 popular real time operating system available in the depends upon the work.
1. pSOS (Portable Software On Silicon) : Name of the RTS : Portable Software On Silicon (pSOS)
Application: PSOS based application development has schematically been shown in fig 1. the host
computer is typically a desktop that supports both Unix & windows host. The target board contain the
embedded processor, ROM, RAM etc. The host computer runs the editor, cross compiler, source level
debugger and library routines. Psos+ and other optional modules such as PAN+,PHILE and PROBE are
instell on a RAM on the terget board. PAN+ is the network manager thats thats provides TCP/IP
communication between the host abd the terget over ethernet and FDDI. It conforms to unix 4.3 socket
syntex and is compatible with other TCP/IP based networking standerds search as ftp and NFS. PROBE+
is a terget debugger and XRAY+ is the Source level debugger. XRAY+ invokes PROBE+ to provide a
seamless debugging enviroment to real time application developer. The application development is done
on the host machine and download to the terget board. The application is debugged using the source
debugger(XRAY+). During application development the application on to a RAM on the target. Once the
application runs satisfactorily, it is fused on the ROM.
Develop by: pSOS (Portable Software On Silicon) is a realtime operating system (RTOS), created in about
1982 by Alfred Chao, and developed/marketed for the first part of its life by his company Software component
group (SCG). In the 1980s pSOS rapidly became the RTOS of choice for all embedded systems based on the
family architecture.
Scheduling Algorithm:
Static table driven: The feasibility and schedule are determined statically. A common example is the
cyclic executive, which is also used in many large-scale dynamic real-time systems. It assigns tasks to
Scalable solutions maximize your flexibility in making performance, functionality, and size tradeoffs
MMU support enhances reliability and optimizes performance through fine-grain cache control
Standard POSIX interfaces provide familiar, intuitive APIs and ease host-based prototyping
Disadvantages: VRTX runs the Hubble Space Technology. Specification : VRTX is a POSIX-RT compliment operating system from mentor graphics. VRTX has
been certified by USFAA(Federal Aviation Agency) for use in mission and life critical application such as avionics
3. VX WORKS REAL TIME OPERATING SYSTEM
Name of the RTS: VX WORKS Real-Time Operating System
Application: Vx Works is a product from wind rader systems. It is host terget type real time os and the
host can be either a windows or a Unix machine. Vx works conforms to POSIX-RT and comes with an
integrate development enviroment (IDE) called tornado. In addition to the standers support for program
development tool search as editor, cross compiler, cross debugger, etc. Tarento contains VxSim and Wind
view. VxSim simulate a Vx Works terget for use of a prototyping and testing enviroment in the absent of
the actual terget board for wind view provide debugging tools for the simulator enviroment, VxMP is the
multiprocessor vertion of Vx Works.
Develop By : VxWorks is a real time OS developed as proprietary software by wind river system of
Alameda, California USA. First released in 1987, VxWorks is designed for use in embedded system.
Scheduling Algorithms: 1. Vxworks uses Priority Based scheduling algorithm. It can be preemptive or round robin. What it
means is task of higher priority will be occupy the CPU.
In case of tasks of same priority following will apply:
a. In Preemptive priority based Scheduling, Task will run on First come first served basis and
will not give up CPU unless other higher priority task /Interrupt comes.
b. In Round robin, ready tasks of same priority will share the CPU fairly.
In VxWorks, tasks are given a priority ranging from 0 to 255 corresponding to the highest to the lowest priority respectively (note the inverse relationship). Board support and system critical tasks fall within the priority range of 0-99. Application tasks fall in the range 100-255 and should never be higher priority than 100. The command sp defaults to priority 100. VxWorks supports two scheduling algorithms, Preemptive Priority Scheduling and Round-Robin
Scheduling with Priority. The default is Preemptive Priority Scheduling.
In this scheduling algorithm, the highest-priority task is given the CPU all of the time until it
blocks or completes. When a task of higher priority than the one currently running is spawned,
the running task is preempted and the CPU is given over to the new task. Once this task
completes, the previous task will resume execution, so long as there is not another task of
higher priority waiting to run. The key defect with this scheduling algorithm arises with tasks of
equal priority. When multiple tasks of equal priority are running, one may never be allocated
processor time if another task of the same priority never blocks. Before proceeding with the task
scheduling, we need to calibrate the dummy loops in order to have reasonably precise
computation times for the tasks. We are interested in finding how much iteration corresponds to
a time tick. The Calibrate() in the EDF implementation runs this task. In the Tornado Shell we
should see a message similar to the following.
Multiprocessor: Vx Works is a multi processor OS.
Advantages : VxWorks is Unix-based Binary, counting, and mutual exclusion semaphores with
priority inheritance Error handling framework Fast, flexible inter-process communication including
TIPC
Full ANSI compliance and enhanced C++ features for exception handling and template support.
Disadvantages: It seems VxWorks get less stable without MMU memory protection. Several
developers experiences that the OS crashes if only one single task crashes.
VxVMI has to be purchased separate to receive MMU memory protection.
Using only a single address space increases the difficulty building applications for VxWorks in for
instance C or C++ not being able to assume that you have got the whole address space for yourself.
Specification : Innovative real-time embedded systems need a robust real-time operating system
(RTOS) that leverages the latest and greatest enhancements in processor and hardware technology.
Proven: VxWorks is the RTOS that powers more than 1 billion real-time systems across the globe, from
small consumer products to commercial airliners. When the consequences for failure are expensive or,
worse, life threatening, VxWorks RTOS is the only choice. After 30 years of RTOS leadership and
consistently successful deployments, Wind River is the name you know you can trust.
Optimized: VxWorks RTOS has been optimized for performance, determinism, and code footprint on
each processor platform it runs on. VxWorks RTOS is also optimized for specialized hardware support
for such features as network acceleration and graphics. Why waste processing power on a non-optimized
RTOS?
Innovative: VxWorks is leading the market in RTOS innovation. The first RTOS with 32-bit and 64-bit
processing, multi-core and multi-OS support, and diverse connectivity options, VxWorks provides our
customers with the leading-edge RTOS functionality they require to stay competitive. Why go with an
RTOS that doesn't provide the solutions you need to take advantage of the latest technology?
4. QNX Real time OS
Name of real time OS : QNX
Application: Qnx is intended for use in mission critical application in the areas such as medical
instrumenttation, internet routers, telemetric device, process control application and air traffic
control application .
Develop By : . The product was originally developed by Canadian company QNX Software
Systems, which was later acquired by Research In Motion.