Real-Time Systems
Introduction
Dr. C.H. Wei
Southern Taiwan University of
Technology
Real-Time Operating
Systems (RTOS):
•Operation System (作業系統)
•Embedded System (嵌入式系統)
•Real Time System (即時系統)
•Real Time Embedded System (嵌入式即時系統)
History and Future of MCU (1)
M units
Over 60億片 in 2003
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
4-Bit
8-Bit
16-Bit
32-bit+
By SEMICO
In last 20 years, 8 bits MCU were domestic
Application of embedded 32Bits MCU grosses rapidly
History and Future of MCU (2)
Total MCU Market (to 200億$)
$20,000
$M
$15,000
$10,000
$5,000
$0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
4-Bit
8-Bit
16-Bit
32-bit+
Conclusion: for 8/16/32 bits MCU, 1/3 + 1/3 + 1/3
By SEMICO
Problems on MCU Education
• Start from Z-80
• An 8051 for everything (should be CSIC)
• Use Simulators
•
•
•
•
Education switches to 8/16/32 bits in parallel
JTAG ONCE BDM replaces the simulator
RTOS should be introduced
Need renew platforms for education
Typical Embedded System
P
O
W
E
R
KEYP
AD
Real Timer
GSM
MODULER
LCD
DISPLAY
MAG
CARD
READER
MCU·CORE
IrDA
Interface
RS232
Interface
IC
CARD
READER
Memory
&
Decoder
Thermal
Printer
Why RTOS?
allows you to divide an application to multitasks; Simplify the application programming:
• Easier to modify, extend, maintenance
• Guarantee the system latency reach or close to
the theoretical limits
• Higher the reliability and system performance
Fill the gap between application engineer & expert
of Computer
Multi-Tasks Bring Problems !
Races in tasks
 Died lock
 priority inversion
 Reentrancy
 Communications between tasks
……

RTOS takes care of all above problems for you!
• RTOS is a nice tool for Embedded System
• You have to LEARN How to Use It!
Commercial RTOS Products
VxWorks Wind RiverSystem
$40k/s & royalty
wrs.com
pSOS
Wind RiverSystem
wrs.com
VRTX
Microtec
$20K/seat
LynxOS $10K/s, Bulue Cat Linux $2.5k/seat
lynuxworks.com
QNX
QNX
qnx.com
OS-9
Microware
Microware.com
Nucleus Accelerated Tech. $20K/s with source code
CMX 8051Tools Tasking
$1.29k
Tasking.com
RT/Studio IDE
Precise
$30K
psti.com
Embedded Linux Green Hill
$7.9K Royalty free ghs.com
Embedex Linux
Lineo
$5k/seat
lineo.com
Redice Linux
Redsonic
redsonic.com
Yellow Dog linux, Hard Hat Linux, Turb Linux Montavista.com
Other: Linuxnews.com LinuxDevices.com
Embed.com
The μC/OS Book
1992
Licensing:
You do not need a license
to use this code in your
application, if your
application is distributed in
object format. You should
however, indicate in your
product literature that you
are using μC/OS, the Real
Time Kernel. If you
distribute μC/OS in source
code, you must obtain a
license.
The µC/OS-II
Book
1998
License policy
changed since
µC/OS 1.0:
You must obtain an Object
Code Distribution License
to embedded µC/OS-II in
commercial product that is
sold with the intent to
make profit
No licensing is required
if µC/OS-II is used for
education
The 2nd edition of
µC/OS-II June 2002
From 498 pages to 606
pages Delete 150 pages
source code list.
250 new pages more
From 12 Chapters to 18
Chapters
Meet Requirement for
Safety-Critical System
June 2003
584 pages
µC/OS (V1.08) vs. µC/OS-II(V2.00)
266 page to 498 pages

Add more important functions:

Memory manager

stack usage check

CPU load check
µC/OS-II (V2.00 1998) vs. µC/OS-II(V2.52 2002)
“MicroC/OS-II The Real-time Kernel”
The Second Edit (2002) Add 250 pages more
Meet Requirement for Safety-Critical System
Certified by FAA
Add more important functions:
Mutax Semaphore, Event Flag , Debug……
Add more explanations
Add Porting and Testing
Real-Time Systems
Mar. 2000
12 Chapters,
610 pages
Real-Time Systems
1.
2.
3.
4.
5.
6.
7.
8.
9.
Jane W.S. Liu
Introduction
Reference Model for Real-Time Systems
Scheduling Approaches
Clock-Driven Scheduling
Practical Aspects of Cyclic Executives
Priority-Driven Scheduling
Resource Access
Aperiodic and Sporadic Tasks
Operating Systems Issues
Scheduling in SystemVR4
Preemption Latency in Linux
I/O Handling in Windows NT/2000
10. Data Caching in Real-Time Systems
11. Real-Time Communication
12. IETF Integrated Services
13. Network Calculus
Real-Time Systems
Jan. 1997
9 Chapters,
448 pages
Real-Time Systems
C. M. Krishna and K. G. Shin
1. Introduction.
2. Characterizing real-time tasks and systems.
3. Task assignment and scheduling.
4. Programming languages and tools.
5. Real-time databases.
6. Real-time communication.
7. Fault-tolerance techniques.
8. Reliability evaluation techniques.
9. Clock synchronization.
Appendix. Review of modeling techniques.
Real-Time Systems
Mar. 2001
10 Chapters,
224 pages
Real-Time Systems and Software
Alan C. Shaw
Introduction: The World of Real-Time
Systems.
2. Software Architectures.
3. Requirements and Design Specifications.
4. Systems of State Machines.
5. Declarative Specifications.
6. Deterministic Scheduling.
7. Execution Time Prediction.
8. Keeping Time on Computers.
9. Programming Languages.
10. Operating Systems.
Appendix: Air Traffic Control System — Project
Specifications.
1.
Real-Time Concepts
for Embedded
Systems
July 2003
16 Chapters,
294 pages
Real-Time Concepts for Embedded Systems
1. Introduction
2. Basics of developing for embedded systems
3. Embedded system initialisation
4. Tasks
5. Semaphores
6. Message queues
7. Other kernel objects
8. Other RTOS services
9. Exceptions
10. I/O subsystem
11. Memory management
µC/OS Already Widely Used in Many Fields

Already used in the field since 1992 such as:





cameras
medical instruments
musical instruments
engine control




network adapter
highway telephone call box
ATM machine
industrial robots……
Since 1995, ported it to MC68HC11, M68000,
CPU32,M.core,HC08 and used it in several projects:


Digital Data Log
MCU based TCP/IP stack
µC/OS, µC/OS –II the RT Kernel






Dedicated Designed for Embedded System
Priority based preemptive kernel (simple
algorithm)
Above 90% is written in C, easy for porting
Scalable and ROM able
Source code for PC environment attached
with a CD
Very detail explanation in excellent
programming style
So good for education!
RTOS Kernel Source Code
µC/OS-II Service
OSTaskCreat()
OSTaskDell()
RTOS
Kernel
Enter_Critical()
Exit_Critical()
Schedule_lock()
ScheduleUnlock()
TaskChangePrio()
…...
Available Compilers
• Diab data (now part of Windriver)
– ANSI-c / c++
– Platforms: windows 95, windows NT, OS/2, Solaris, SunOS, HP/UX, IRIX, aix,
– Http://www.WindRiver.Com/products/html/dcc_compiler.Html
• Green hills
– Standard C++, extended embedded C++
– Host platforms: windows 95, 98, NT and sparc/solaris
– Http://www.Ghs.Com/products/mcore_development.Html
• Hiware
– ANSI-C / C++ / EC++ / cc++ compilers
– Host platforms: windows 95, 98, NT
– Http://www.Hiware.Com/p_mcore.Html
• Metrowerks
– ANSI C compliant, ANSI/ISO C++ compliant and EC+ compilers
– Host platforms: windows 95, 98 and NT
– Http://www.Metrowerks.Com/embedded/mcore/
• Motorola GNU toolkit
– GNU C and C++ compilers
– Http://sarl.Corp.Mot.Com/mcore/gnu/
Free C Compile: GNU gcc Tolls
•GNU gcc Tools
•Cross C Compiler for:
M68K, CPU32, Coldfire, M.Core, PowerPC,
68HC11/12,SPARC,PA,RISC,VAX,AMD29K,
ARM,Thumb,MN10xxx, M32, SR6000,MIPS,
RT, i386, Inter960,TMS32, DEC alpha, V850,NS32K
•Cross assembler : AS
•Disassemble: Objdump
•Liker: Ld
•C support lib: Libc & Libm
•Gcc Debug options
–You know GCC , You will get also Embedded ucLinux
Porting µC/OS –II
• Compiler with Hiware
• Down loaded with Picobug
Or:
• Compiler with CodeWarrior
• Down loaded with EDBI tool
uCLinux in Linux
• Take off the Memory Management
– Good for the non-mmu CPU in Embedded
•
•
•
•
Free OS for Embedded
Many application program in Linux available
Not a Real Time OS !Download RTLinux3.1 from:www.rtlinux.org
Much smaller than Linux, sometimes still too large
for Embedded system typical RAM usage ~512K
• Down load from: www.uclinux.org