CS3369: Real Time Computer Control
Software
 Who I am:
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Dr. Lusheng WANG
Dept. of Computer Science
office: Y6429
phone: 2788 9820
e-mail: lwang@cs.cityu.edu.hk
web site: http://www.cs.cityu.edu.hk/~lwang
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Suggested References:
• D.M. Auslander and C.H. Tham, “Real-time software
for control: Programming examples in C”, Prentice
Hall, USA, 1990.
• S. Bennett, “Real-time computer control: An
introduction”, Prentice Hall, UK, 1988.
• Babu Joseph, Real-time personal computing (for data
acquisition and control), Prentice Hall, Englewood
Cliffs, New Jersey, 1989.
• P. Norton, P. Aitken, R. Wilton, “PC Programmer’s
Bible”, 1993.
• Turbo C, User Guide, ver. 2.0 Borland International, 1988
• Dr. James T. Smith, “Advance Turbo C”, McGraw-Hill
Book Company, 1989.
• H.M. Deitel and P. J. Deitel, “C++ How to program”,
Prentice Hall, 1998.
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Four Parts of the Course:
 Introduction to real time systems and basic
computer organization
 Real time scheduling
 Real time system development methodology
 Real time programming
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What I Cover:
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some basic concepts in real time embedded systems
computers organization
programming in C++
interrupts and controls
top down design
requirements specification
program testing
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Evaluation of the Course
 Course work: 40%
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Two Assignments. 20% each.
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I give you time in the labs to do the two assignments.
Project:
optional. 10% bonus for the course work.
 A final exam:
60%;
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How to Teach
Contents are divided into four classes
1. Basic part -- every body must understand in order to pass
2. Moderate part -- most of students should understand.
Aim at B or above.
3. Hard part -- used to distinguish students.
Aim at A or above.
4. Fun part -- just illustrate that some interesting things
can be done if one works very hard.
-- useful knowledge that will not be tested.
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How to Learn
1. Attend every lecture and tutorial. (4 hours per week)
2. Try to go with me when I am talking
3. Ask questions immediately
4. Try to fix all problems during the 2 hours tutorial
5. Ask other students to help during the lab.
Every student should be able to finish basic part in tutorial/lab.
Most of students should be able to finish the moderate part
in tutorial/lab.
If you do the above, you should be able to get at least B+.
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 Real Time Embedded Systems
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Computer systems that operate as an integral part of
physical systems, and very often, react and readjust
control variables quickly to the changes in physical
systems.
Functionality:
• monitor equipment performance
• timely control equipment operations
• provide human-machine interfaces
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 Three types of Real Time Embedded Systems
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Hard: Each job enters the system with a deadline
before which it has to be served. Later response is
not allowed.
Soft: The average response time for the jobs is to be
minimized.
Firm: A combination of soft and hard real time
requirements.
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 Examples of Real Time Embedded Systems:
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Air-conditioning Control
Elevator Control
Traffic Light Control
Video Games
TV Remote Control
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Introduction to Computer Hardware
We will learn the following:
1. Architecture of computer hardware
2. Execution of an instruction
3. Execution of a program
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Basic hardware components
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Central Processing Unit
Memory
Input/Output Sub-systems
Buses
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Architecture of Computer Hardware
cpu
General
Purpose
Registers
Arithmetic and
Logic Unit
Control
Unit
data/address/control buses
Main
Memory
Input/Output
Interfaces
Peripherals
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What Does a Computer Do?
Do some computation according to users’ willing
1. Users tell computers what to do via programs.
2. A program is a sequence of instructions.
3. Instructions are the basic operations computers can do.
4. Examples of Instruction
add 2, 3
(compute 2 + 3)
sub 4, 2
(compute 4 - 2)
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An Example of a Program
The instructions are executed sequentially
There are some instructions allow jump
x=3*5+6-7; (High level language)
x=3;
x=x*5;
x=x+6;
x=x-7;
(Low level language)
(A set of instructions)
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Central Processing Unit (CPU)
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Execute program stored in the main memory by
fetching their instructions, examining them and then
executing them one after another
Components of CPU
1.Arithmetic logical unit (ALU) – performs operations such as addition and
boolean AND needed to carry out the instructions
2.Registers – high-speed memory used to store temporary results and
certain control information used by the CPU. CPU registers such as
program counter (PC), instruction registers (IR), status registers
3.Control unit (CU) – fetching instructions from main memory and
determining their type
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Memory
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part of the computer where program and data are stored and
to be processed by the processor
Also called Main Memory, Random Access Memory (RAM)
Bits - the basic unit of memory is the binary digit, a bit
contains a "0" or "1".
Memory contains many bits organised in linear order.
Several bits form a “cell” containing a piece of information
(data, instruction, integer, character, etc)
The size of the cell can be a byte or several successive bytes.
Each cell has a reference number, called its address, by
which program can refer to.
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Buses
 Communication links allowing data, instructions and
memory addresses to be referred between different
components (CPU, main memory and I/O devices) in a
computer system.
 Example:
 UNIBUS - Digital Computer Inc.,
 PC Bus - Industrial Standard PC bus
 Peripheral Component Interconnect (PCI) Bus
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Input/Output Device
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Input Devices
• Allows computer user to issue commands, asks for
information, adds new data and programs to the
computer.
• The computer receives input from the press of a key
or button, touch of a finger on a screen, optical
scanners, spoken words and many sources.
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Output devices
Display results to the user. Includes video display screen, printers,
audio speakers.
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General
Purpose
Registers
Arithmetic and
Logic Unit
Control
Unit
data/address/control buses
Main
Memory
real-time clock
disk drive
digital signals
CD Drive
pulse operations
printer
analog-to-digital
conversion
Key board
digital-to- analog
conversion
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Input/Output
Interfaces
…...
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Display
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Execution of an Instruction
Execution of
an instruction
is achieved by
a sequence of
commands
issues by the
control unit.
Fetch the instruction from the memory
Fetch the operands from the memory
Perform the operation
Update the program counter
no
Check interrupt
yes
Interrupt processing
Next Instruction
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Execution of a Program
Fetch the instruction from the memory
Fetch the operands from the memory
Perform the operation
Update the program counter
A program is
a sequence of
instructions.
no
LOAD b, R1
Check interrupt
yes
Fetch the instruction from the memory
Fetch the operands from the memory
Perform the operation
Update the program counter
no
Check interrupt
yes
ADD R1, 1
a = b + 1;
Fetch the instruction from the memory
Fetch the operands from the memory
Perform the operation
Update the program counter
no
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STORE R1, a
Check interrupt
yes
…...
CS3369 Real Time Control
Software/WANG Lusheng
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Computer Languages
Users use languages to write instructions and programs.
There are lots of computer languages that can be classified
into two categories -- low level and high level languages
Low Level Languages:
Machine language -binary code
Assembly language
Examples of Low Level Languages:
ADD A3, D5
1101 101 001 001 011
Assembly instruction
Machine language
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High Level Computer Languages
English-like languages -- easy to handle for users
-- computers cannot directly understand
Examples: C, C++, PASCAL, LISP, COBAL, etc
Running a program written in high level languages:
1. Compile the program
(translate the high level language into a machine
language. Done automatically by a software called
compiler.)
2. Execute the translated code. (executable code)
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The First C Program
#include<stdio.h>
int main(void)
{
printf(“Hello, world! \n”);
return 0;
}
Output:
Hello, world!
\n stand for “new line”
It will not be shown on the screen
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The First C++ Program
#include<iostream.h>
/* to include the file iostream.h
*/
int main(void)
{
cout <<“Hello, world! \n”;
return 0;
}
/* part of every C++ program
*/
Output:
Hello, world!
/* { The beginning of main function */
/*print out Hello, world! On screen */
/* exit a function
*/
/*} The end of main function
*/
\n stand for “new line”
It will not be shown on the screen
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The first program for computation
#include <iostream.h>
int main(void)
{
int x,y;z;
Note that, there are three variables
x, y, and z. All are of type integer.
Each integer variable can store
an integer. The variable itself has
an address, which is automatically
assigned by the system (computer).
x = 1;
y = 2;
z = x+ y;
cout <<“The sum of x and y is” << z;
return 0;
}
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The address of a variable
 In C, the address of a variable can be known by user.
#include <iostream.h>
int main (void)
{
int x;
cout <<“The address of x is” << &x;
return 0;
}
Output: -134219164
Note that, each execution gives a different address.
Exercise: Try to run the program three times. What happens?
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Examples of C++ Programs We
Intend to Deal with
Print out a person that can move
Some program about graphics (G1 and G2)
Time Delay-- create movies (G3, also person)
Move keys with interrupts (key)
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Summary
1. Real time embedded systems.
2. Computer architecture
3. Memory
4. Execution of instructions and programs.
5. C++
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