RTOS types, RTOS architecture

1. RTOS - FREERTOS

2. OVERVIEW
• RTS
• History
• OS
• RTOS

3. REALTIME SYSTEM
• RTS – results produced within a specified deadline
• RTS describes hardware and software systems subject to a ”real-time
constraint”, for example from event to system response.
• RTS is one whose logical correctness depends on the correctness of its
outputs as well as their timeliness.1
• Many contend that all computer systems are real-time. All systems have a
response-time.

4. In the 1940s
► War effort pushed the boundary of
technological process.
► Preparation of ballistics tables, aircraft
systems, atomic weapons design, fire control,
and logistics.
► Von Neumann, Bell labs and MIT were at the
forefront.
► Gave rise to project Whirlwind in 1947. Pilot
trainer/simulator.Ferrite Core memory - 10 µs
access times.incorporated into SAGE air
defense system.

5. In the 1950s
► The race to build faster and energy efficient computers and real-
time systems.
► IBM had significant impact on research.
► Their Military Products Division worked on processing centers for
SAGE and aiming for B-52 systems.
► The SemiAutomatic Ground Environment(SAGE) air defense
system project
) Maintain up-to-date picture of air and ground situation
) Control modern weapons rapidly and accurately
) Present pictures to Air Force
► A real time control, real-time communication and real-time
information management system.
►Other Projects include
• IBM SABRE - Electronic reservation system for AA(American Airlines).
• IBM Hardware - IBM 700 machine series
• Project Stretch - All-transistor computer developed in 1954

7. In the 60s
►BELL Laboratories Involved in the development of Naval gunfire-control system.
►BELL- Major involvement is real-time switching system.
►BELL - Stored Program Control(SPC) was a big breakthrough in real-time telephone
communications
► Significant non-military research split into computational and commercial interests.
► Industries like petroleum industry and chemical manufacturing used real-time control.
► IBM worked on NASA’s real-time computer for manned space program.
► Project Mercury was used to compute spacecraft orbit go/no-go computation in 10 seconds.
Project Gemini succeeded Project Mercury.
► Project Apollo was used for tracking of Apollo spacecraft.
► Its successor project space shuttle implemented pinpoint landing, data processing and very high
flight rate.

9. Soft RealTime Systems
• In a soft real-time system, it is considered undesirable, but not
catastrophic, if deadlines are occasionally missed.
• Also known as “best effort” systems
• Most modern operating systems can serve as the base for a soft real time
systems.
• Examples:
– multimedia transmission and reception,
– networking, telecom (cellular) networks,
– web sites and services
– computer games.

10. Hard RealTime System
• A hard real-time system has time-critical deadlines that must be met; otherwise a
catastrophic system failure can occur.
• Absolutely, positively, first time every time
• Requires formal verification/guarantees of being to always meet its hard deadlines
(except for fatal errors).
• Examples:
– air traffic control
– vehicle subsystems control
– Nuclear power plant control

11. Firm RealTime System
• Needs to follow deadlines
• Missing a deadline may not have big impact but could cause undesired affects, like huge
reduction in quality of product
• Example: Multimedia applications, Robotic assembly line, Financial forecast system

12. Generation Era O/S used Feature
First 1945-55
Vacuum tubes
ENIAC EDVAC
Analog
computers
No O/S Plug in boards
Jumper wired
Second 1955-65
IBM 1401, 7094
Batch O/S (Not interact
system)
Paper tape
Punched cards
Offline printing
Third 1965-80
IBM 360
Time sharing O/S (many at the
same time PDP-II
Spooling (On-line)
Multiprogramming
Fourth 1980-90
IBM 360
MS-DOS UNIX User friendly. He need
not know about
computer
Fifth 1990 KBCS
(Knowledge based
computer system)
Distributed O/S
Network O/S
More advanced
OS EVALUATION

13. General Purpose Operating System
• Interface between users and hardware
• Controlling and allocating memory
• Controlling input and output devices
• Managing file systems
• Facilitating networking

14. Types of OS
 OS can be of two types as follows:
 General Purpose Operating Systems (GPOS)
 Real Time Operating Systems (RTOS)
 Where and all the OS can run?
• PC
• Server
• Embedded device
OS Responsibilities
Co-ordinates:
 Security
 Communication
 Resource mgmt.
Service provider:
 File system
 Device access
 System utilities
 System services

15. OS COMPONENTS
• Kernel : Core components of the OS
• Process Scheduler:
• Determines when and for long each process executes
• Memory Manager:
• Determines when and how memory is allocated to processes
• Decides what to do when main memory is full
• File System:
• Organizes named collections of data in persistent storage
• Networking:
• Enables processes to communicate with one another

16. OS – In action
 CPU loads boot program from ROM (e.g. BIOS in PC’s)
 Boot program:
 Examines/checks machine configuration (number of CPU’s, how much memory, number & type of hardware
devices, etc.)
 Builds a configuration structure describing the hardware
Loads the operating system, and gives it the configuration structure
After basic processes have started:
 The OS runs user programs, if available
 Otherwise enters the idle loop
In the idle loop:
 OS executes an infinite loop (UNIX)
 OS performs some system management & profiling
 OS halts the processor and enter in low-power mode (notebooks)
OS wakes up on:
 Interrupts from hardware devices
 Exceptions from user programs
 System calls from user programs
Twomodes of execution:
 User mode: Less privilèges
 Supervisor mode: Unrestricted access to
everything (OS)

17. Types of Operating Systems
There are three types of operating systems based on their application
• Stand-Alone Operating System
• It is a complete operating system that works on a desktop or notebook computer. Example: DOS,
Windows 2000 professional, Mac OS X
• Network Operating Systems
• It is an operating system that provides extensive support for computer networks.A network OS
typically resides on a server. Examples:Windows 2000 server, Unix, Linux, Solaris
• Embedded Operating Systems
• OS on handheld computers and small devices. It resides on a ROM chip. Examples:Windows CE,
Pocket PC 2002, Palm OS

19. RTOS
► IBM’s first RTOS, the Basic Executive was developed in
1962. Minimum function, it had interrupt handling and
I/O driver support. Succeeded by Executive II in 1963.
► Executive II provided disk residence for user and
system programs.
► The third RTOS, FORTRAN Executive, Build the
foundation for future high-level languages in real-time
system.
RTOS
OS
components
Tasks
Synchroniza
tion
Inter Task
communica
tion
Real Time
& OS

20. Why Use a RTOS?
 Task prioritization can help ensure an application meets its processing
deadlines
 Abstracting away timing information from applications
 Good Maintainability/Extensibility
 Good Modularity with tasks
 Well-defined interfaces support team development
 Easier testing with well-defined independent tasks
 Code reuse
 Improved efficiency with event-driven software
 Idle task when no applications wishing to execute
 Flexible interrupt handling
 Easier control over peripherals

21. Structure of RTOS
Custom-Hardware
RTOS-kernel
Applications
BSP

22. Function of RTOS
• Task Management
• Interrupt handling
• Memory management
• Exception handling
• Task synchronization
• Task scheduling
• Time management

23. Component of an RTOS
• Process (task) management
• Scheduler
• Synchronization mechanism
• Interprocess communication (IPC)
• Semaphores
• Memory Management
• Interrupt service mechanism
• I/O management, H.A.L Layer
• Development environments
• Communication subsystem
• Board Support Packages

24. Features of RTOS’s
• Scheduling.
• Resource Allocation.
• Interrupt Handling.
• Predictability
• Timeliness
• Reliability
• Fault tolerant
• Efficiency of system components

25. FreeRTOS Firmware Stack

27. TERMS USED IN RTOS
Essential terms used in RTOS:
• Task – A set of related tasks that are jointly able to provide some system
functionality.
• Job – A job is a small piece of work that can be assigned to a processor, and that
may or may not require resources.
• Release time of a job – It’s a time of a job at which job becomes ready for
execution.
• Execution time of a job: It is time taken by job to finish its execution.
• Deadline of a job: It’s time by which a job should finish its execution.
• Processors: They are also known as active resources. They are important for the
execution of a job.
• Maximum It is the allowable response time of a job is called its relative deadline.
• Response time of a job: It is a length of time from the release time of a job when
the instant finishes.
• Absolute deadline: This is the relative deadline, which also includes its release

29. TYPES OF RTOS
Commercial RTOS
1. VXWorks
2. QNX
3. Windows CE
4. Spring Kernel
5. VRTX (virtual Real-Time Executive)
6. BeOS
7. ChorusOS
8. RMX
9. RSX-11
10. PSOS
11. OSEKtime
Open Source RTOS
1. eCos
2. FreeRTOS
3. RTLinux
4. RTAI
5. MicroC/OS-II
6. Nut/OS
7. TRON