fundamentals of unit 1 fundamentals of embedded systems
TRANSCRIPT
Fundamentals of Embedded SystemsUNIT 1 FUNDAMENTALS OF EMBEDDED
SYSTEMS
Structure Page Nos.
1.0 Introduction 51.1 Objectives 51.2 Embedded System: An Introduction 6
1.2.1 Components of an Embedded System1.2.2 Block Diagram and Characteristics of an Embedded System1.2.3 Classification of an Embedded System
1.3 Embedded Operating System 81.3.1 Classification of an Embedded Operating System
1.3.2 Characteristics of an Embedded Operating System1.4 Requirements and Specification in Embedded System 101.5 Programming Languages for Embedded System and Classification 12
1.5.1 Hardware Languages1.5.2 VHDL V/s Verilog
1.6 Selected Embedded System applications 141.6.1 Washing Machine1.62. Digital Sound Recorder
1.7 Summary 191.8 Answers/Solutions 191.9 Further Readings and References 19
1.0 INTRODUCTION
Embedded systems are basic electronic devices used to control, monitor or assist the operation of equipment, machinery or a plant. The choice of word “embedded” reflects the fact that these are integral part of the system. Uses of embedded system in our real life are increasing day by day. Children need such systems to play video games and to operate chocolate vending machine, Housewives need embedded systems for microwave, TV, music system, and other system appliances.
In this unit you will learn about basics of embedded system: its uses, its components, its basic requirements in terms of Hardware and Software and support of Programming Languages. We will also highlight some application of embedded system in our real life scenario at the end of this unit.
1.1 OBJECTIVES
After going through this unit, you will be able to:
• define embedded operating system;
• identify Basic Requirements and its Specification;
• explain Design methodology;
• describe the use of programming languages in embedded system; and
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• list the use of applications of Embedded System.
1.2 EMBEDDED SYSTEM: AN INTRODUCTION
An embedded device can range from a relatively simple product for ex. a toaster to complex mission critical applications such as those used in avionics. A typical embedded device will have both hardware and software components. The hardware could be micro components such as embedded microprocessor or microcontroller. Microcontroller is relatively small, has a onchip memory, an I/O controller and other supported modules to do processing and controlling tasks. The software consists of applications that perform dedicated tasks and may run on Real time operating system which will be explained later in this unit.
Embedded System may be either an independent system or a part of a large system. It is specialized computer system but not a general purpose workstation like a desktop or a computer. Such kind of systems is housed on a single microprocessor board with programs which are stored in ROM (Read Only Memory). Embedded system is usually a compact, portable and mass produced electronic devices. In the early days, embedded systems were designed using microprocessors like 8085. But nowadays, we are using a wide range of processors from other manufacturers.
Before we want to the basic of an embedded system, we should see a wide range of its applications. In fact, almost all modern electronic devices use some sort of embedded system technology inside them and we always come across such devices: DVD players, air conditioners, printers, attendance machines, handphone, digital camera, ATM machines, we will see some examples of embedded system in section 1. Now it is time to give a proper definition.
Definitions: “Embedded Systems are devices which are used to control, monitor or assist the operation of an equipment, machinery or plant”. The term “control” defines the main function of Embedded System because their purpose is to control an aspect of a physical system such as pressure, temperature and so on. Also the term “monitor” defines the progress of activities.
Where do we use Embedded Systems? From several examples listed earlier these systems are extremely common in the home, vehicle and the workplace.
• At Home: Washing Machines, dishwashers, ovens, central heating system, burglars alarms, etc.
• In Motor Vehicle: Engine management, security (locking or antitheft devices), air conditioning, brakes, radio etc.
• In Industry & Commerce: Machine control, factory automation, robotics, electronic commerce office equipments.
1.2.1 Components of an Embedded System
An embedded system has three main components : Hardware, Software and time operating system
i) Hardware
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Fundamentals of Embedded Systems• Power Supply
• Processor• Memory • Timers• Serial communication ports• Output/Output circuits• System application specific circuits
ii) Software: The application software is required to perform the series of tasks. An embedded system has software designed to keep in view of three constraints:
• Availability of System Memory• Availability of processor speed• The need to limit power dissipation when running the system continuously in
cycles of wait for events, run , stop and wake up.
iii) Real Time Operating System: (RTOS) It supervises the application software and provides a mechanism to let the processor run a process as per scheduling and do the switching from one process (task) to another process.
1.2.2 Block Diagram and Characteristics of an Embedded System
Embedded systems are executed by a microcontroller, which communicates with the sensors and actuators. It means that a user of an embedded system is not able to change the functionality of the system through modifying or replacing the software because it is kept in ROM.
Figure 1: Embedded System
Figure 1 shows basic components used in Embedded System are as follows:
• Microcontroller: It monitors and controls the environment.
• Sensors: It collects data from environment through input devices.
• Actuators: It displays the system's status through output devices.
• Timer: It provides response within a certain time frame.
Characteristics of Embedded System
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Microcontroller
Sensors Actuators
Embedded System
Input Output
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Some of important Characteristics of embedded system are:
1) Embedded Systems are designed to do some specific task i.e., it is not a general purpose kind of a system.
2) Software for Embedded Systems are stored in ROM or flash memory.
3) Knowledge about behavior at design time can be used to minimize resources and to maximize robustness.
4) Embedded Systems provide low power consumption in many situations.1.2.3 Classification of an Embedded System Embedded system can be classified as:
• Standalone Embedded System: It is built using a specialized communication processor, memory a number of network access interfaces (known as network ports), and special software that implements logic for sending information from one device to another device.
• Real Time Embedded System: A realtime embedded system usually monitors the environment where the embedded system is installed. This kind of system is required to respond in time to a request. Examples of realtime embedded systems are aircraft engine control systems, nuclear monitoring systems and medical monitoring equipment.
• Network Appliances: Network appliances are a new class of embedded systems that in addition to traditional realtime processing must support a broad and changing array of network protocols.
• Mobile Embedded System: Mobile Embedded Systems usually are simple, batterypowered systems with resource limitations. In some situations, their batteries lifetime becomes a prim issue.
1.3 EMBEDDED OPERATING SYSTEM
An embedded operating system (EOS) is a system software that manages all the other programs and devices in an embedded system. It normally guarantees a certain capability within a specified storage size and time constraint as well as with application programs. Its structure is very similar to a structure of a normal operating system however mainly differentiated by some factors such as type of preinstalled device, functional limits, taking designed job only. It also normally has boot loader, OS kernel, required device drivers, file systems for the user data and so forth. At their core, embedded operating systems contain some of the same software components used on larger operating systems, such as windows and Linux etc. larger operating systems (OS), embedded operating systems deals with task switching, scheduling of tasks, memory allocation, etc.
But there are some distinctions between desk top computerOS and embedded system OS. Desktop Computer is a general purpose computing system whereas embedded system purpose is for a specific task. Embedded operating systems have several common characteristics that distinguish such systems from other computing systems:
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Fundamentals of Embedded Systems
• Single Functioned: Usually executes a specific program repeatedly e.g. pager.
• Tightly Constrained: All computing systems have constraints on design metrics, but those on embedded systems can be especially tight. A design metric is a measure of an implementation’s features, such as cost, size, performance and power.
• Reactive and Real Time: Many embedded systems must continually react to changes in the system’s environment and must compute certain results in real time without delay. In contrast, a desktop system typically focuses on computation with relatively infrequent reactions to input devices.
• Secondary Memory: Generally embedded system doesn’t need secondary memory. • Unlike a desktop computer system which may have new software loaded onto it frequently, embedded systems retain the same code for a long time, sometimes indefinitely. Embedded operating systems do not usually include support for external storage or graphical interfaces, or protection from malicious or unstable code. The limited memory in embedded systems requires the operating system and process to work very closely to manage the free resources.
1.3.1 Classification of an Embedded Operating System (EOS)
We can classify Operating Systems (for embedded systems) into two parts called as RealTime Operating Systems and NonRealTime OS as shown in Figure 2.
Figure 2: Classification of embedded operating system
• Real Time Operating Systems are operating systems which guarantee responses to each event within a defined amount of time. This type of operating system is mainly used by timecritical applications such as measurement and control systems. Some commonly used RTOS for embedded systems are: VxWorks, OS9, Symbian, and RTLinux etc.
• NonReal Time Operating Systems do not guarantee defined response times. Those systems are mostly used if multiple applications are needed. Windows and Palm OS are examples for such embedded operating systems.Some other features which are quite common to EOS irrespective of any classification are presented below.
1) Single System Control Loop: Such systems run a single task.
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Embedded OS
Real Time Operating System (RTOS)E.g. VxWorks, OS9, RTLinux
Non Real Time Operating SystemE.g. Windows, Palm OS
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2) Multitasking Operating System: In a multitasking operating system, several tasks or processes appear to execute concurrently
3) Preemptive Operating System: A preemptive operating system is a multitasking operating system that defines preemptive priorities for tasks. A higher priority task always interrupts and is always run before a lower priority task.
4) Rate Monotonic Operating System: Such operating system guarantees that tasks in the system can run at a certain interval of time for a certain period of time. When this guarantee is not met, the system software can be notified of failure and take appropriate action.
5) Constant Time Operations: Constant time operations are the cornerstone of real time responsiveness and predictable capacity loading.
6) Interrupt Response Times: Embedded Operating Systems normally provide for fast interrupt response times by separating interrupt handlers in two phases. In the first phase, the interrupt handler program reacts to an interrupt and satisfies the interrupt condition from a hardware perspective. In the second phase, the interrupt handler processes the interrupt condition. While executing in the second phase, other interrupts in the system are enabled and may be handled to allow higher priority interrupts to take precedence over lower priority interrupts.
7) Priority Inversion: Priority inversion is a condition in preemptive operating systems where a lower priority task claims a resource that is subsequently required by a higher priority task.
8) Monolithic Operating Systems: A monolithic operating system includes all operating system code such as device drivers and file system handlers as part of a single system image.
9) Micro Kernels: A micro kernel operating system includes only the bare necessities such as task switching, scheduling and device handling interfaces in the operating system code.
1.3.2 Characteristics of an Embedded Operating System
For an Embedded OS to be regarded as good, it should have the following features:
• Modularity: Modularity is a concept that has an application in the contexts of computer science, particularly programming language. A module can be defined variously, but generally must be a component of a larger system, and operate within that system independently from the operations of the components of the system.
• Scalability: The property of a multiprocessing computer that defines the extent to which addition of more processors increases aggregate computing capability. Windows NT server 4.0 is generally considered to be scalable to eight Intel processors.
• A CPU support: There is no meaning of an OS without a compatible CPU.
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• Flexibility and Configurability: By flexibility we mean to say that the Embedded OS must be adjustable to change/modification. A configuration is an arrangement of functional units according to their nature, number, and chief characteristics. Often, configuration pertains to the choice of hardware, software, firmware, and documentation. The configuration affects the system function.
• Have a small footprint: In computer science, the footprint of a piece of software is the portion of computing resources, typically RAM, CPU time peripheral devices.
• Have a large Device Driver Database: The larger the Device Driver Database of an Embedded OS, the greater is the number of devices that can be controlled through that particular OS.
1.4 REQUIREMENTS AND SPECIFICATION OF AN EMBEDDED SYSTEM
A requirement is a condition needed by a user to solve a problem or achieve an objective. Specification is a document that specifies, in a complete, precise, verifiable manner, the requirements, design, behavior, or other characteristics of a system, and often, the procedures for determining whether these provisions have been satisfied. For example, a requirement for a car could be that the maximum speed to be at least 120mph. The specification for this requirement would include technical information about specific design aspects.
Requirements and specifications are very important components in the development of any embedded system. Requirements analysis is the first step in the system design process, where a user's requirements should be clarified and documented to generate the corresponding specifications. For example, errors developed during the requirements and specifications stage may lead to errors in the design stage. When this error is discovered, the engineers must revisit the requirements and specifications to fix the problem. This leads not only to more time wasted but also the possibility of other requirements and specifications errors. Many accidents are traced to requirements flaws, incomplete implementation of specifications, or wrong assumptions about the requirements.
Establishing good requirements requires people with both technical and communication skills. Technical skills are required as the embedded system will be highly complex and may require knowledge from different engineering disciplines such as electrical engineering and mechanical engineering. Communication skills are necessary as there is a lot of exchange of information between the customer and the designer. Without either of these two skills, the requirements will be unclear or inaccurate.
Example of a System Requirement of an Embedded System:
Embedded System requires minimal hardware requirements as follows:
Minimum Requirements
Operating System
Microsoft Windows NT® Workstation operating system version 4.0 with Service Pack 5 (SP5) or later
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Processor Computer with Pentiumclass processor; Pentium 300megahertz (MHz) or higher processor recommended
Memory 64 MB of RAM
Drive 100 MB for generated image storage 20 MB for installation of the Windows NT Embedded 4.0 development system 170 MB if the Binary Repository is copied to the local development system hard drive (optional)
Optional Microsoft Visual Studio® 6.0 development system to create Target Designer extensions
Specification and Design
A specification enables everyone involved in the process to comprehend the entire design and his/her piece of it. The specification must include the following:
• An external block diagram showing how the device fits into the system.
• An internal block diagram showing each major functional section.
• A description of the I/O pins.
• Physical specification — package type, physical size, connector requirements, and so on.
• Power consumption target • Price target • Test procedures
The design step of Design Methodology depends on the kind of device targeted. Digital hardware differs from analog hardware.
Design Methodology doesn't limit or dictate design practices, but it's important that you use reliable, accepted design practices during this step.
However, system integration and system testing is necessary to ensure that all parts of the system work correctly together. At the system integration and test step of the design, you have the responsibility to determine that the entire system, including the device you've designed, works correctly. You should perform a burnin test to assure that any manufacturing defects are discovered before the product is delivered. If you've followed the procedure up to this point, chances are good that your system will perform correctly. Minor hardware problems can often be worked around by slight modifications to the system or changes to the system software.
1.5 PROGRAMMING LANGUAGES FOR EMBEDDED SYSTEM AND CLASSIFICATION
Embedded systems are applicationspecific computers that interact with the physical world. Each has a diverse set of tasks to perform, and although a very flexible
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Fundamentals of Embedded Systemslanguage might be able to handle all of them, instead a variety of problemdomain
specific languages have evolved that are easier to write, analyze, and compile. The choice of programming language is very important for real time embedded software.
The following factors influence the choice of languages:
• A language compiler should be available for the chosen RTOS (Real Time Operating System) and hardware architecture of the embedded system.
• Compilers should be available on multiple OSs and microprocessors. This is particularly important if the processor or the RTOS needs to be changed in future.
• The language should allow direct hardware control without sacrificing the advantages of a high level language.
• The language should provide memory management control such as dynamic and static memory allocation.
So, we can categorize embedded programming languages in to two parts such as hardware language and software language.
1.5.1 Hardware Languages
A hardware description language can be used to describe the logic gates, the sequential machines, and the functional modules, along with their interconnection and their control, in a embedded system. There are various languages used for this purpose as follows:
VHDL
VHDL is the Very High Speed Integrated Circuit Hardware Description Language. It can describe the behaviour and structure of electronic systems, but is particularly suited as a language to describe the structure and behaviour of digital electronic hardware designs, VHDL is an international standard, regulated by the international languages. VHDL is suitable for use today in the digital hardware design process, from specification through highlevel functional simulation, manual design and logic synthesis down to gatelevel simulation.
VERILOG
Verilog HDL is one of the two most common Hardware Description Languages (HDL) used by integrated circuit (IC) designers. The other one is VHDL. HDL’ allows the design to be simulated earlier in the design cycle in order to correct errors or experiment with different architectures. Designs described in HDL are technologyindependent, easy to design and debug, and are usually more readable than schematics, particularly for large circuits.
Verilog can be used to describe designs at four levels of abstraction:
i) Algorithmic level (much like, C language code with if, case and loop statements).
ii) Register transfer level (RTL uses registers connected by Boolean equations).
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iii) Gate level (interconnected AND, NOR etc.).
iv) Switch level (the switches are MOS transistors inside gates).
The language also defines constructs that can be used to control the input and output of simulation.
1.5.2 VHDL VS. VERILOG
Let us compare between the two languages on the following parameters:
1) Capability
• Hardware structure can be modeled equally effectively in both VHDL and Verilog. When modeling abstract hardware, the capability of VHDL can be achieved in Verilog.
2) Compilation
• VHDL: Multiple designunits (entity/architecture pairs), that reside in the same system file, may be separately compiled if so desired. However, it is good design practice to keep each design unit in it's own system file in which case separate compilation should not be an issue.
• Verilog: The Verilog language is still rooted in it's native interpretative mode. Compilation is a means of speeding up simulation, but has not changed the original nature of the language. As a result care must be taken with both the compilation order of code written in a single file and the compilation order of multiple files. Simulation results can change by simply changing the order of compilation.
3) Data types
• VHDL: A multitude of language or user defined data types can be used. This may mean dedicated conversion functions are needed to convert objects from one type to another.
• Verilog. Compared to VHDL, Verilog data types are very simple, easy to use and very much geared towards modeling hardware structure
4) Design reusability
• VHDL. Procedures and functions may be placed in a package so that they are available to any designunit that wishes to use them.
• Verilog. There is no concept of packages in Verilog. 5) Easiest to Learn
• Verilog is probably the easiest to grasp and understand as compared to VHDL.
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Fundamentals of Embedded Systems6) Operators
• Verilog has a very useful unary operators that are not in VHDL.
• VHDL has the mod operator that is not found in Verilog.
Java and C++ are another programming languages which are used extensively for embedded system design.
1.6 SELECTED EMBEDDED SYSTEM APPLICATIONS
We can categorize applications of Embedded System into various categories as mentioned in Table:
Area ApplicationsAerospace Navigation Systems, Automatic landing systems, Flight
altitude controls, engine controls, space explorationAutomotive Fuel Injection Control, Passenger environmental
controls, antilock braking systems, air bag controls, GPS mapping
Communications Switches, HubsComputer Peripherals Printers,scanners,keyboards,displays,modems,Hard
Disk Drives,CDROM drivesHome Ovens, Washing Machine,Digtal Watch, Security
Alarm, Sound RecorderIndustrial Elevator Controls, Robots, Engine ControlInstrumentation Data Collection, power suppliesMedical Imaging Systems, Patient monitors, Heart pacersOffice Automation FAX machines, Telephones, Cash Registers
Now, we will discuss here two well known applications used for home appliances in detail as follows:
1.6.1 Washing Machine
Washing machine supports three functional modes:
i) Fully Automatic Mode: In fully automatic mode, once the system is started it perform independently without user interference and after the completion of work it should notify the user about the completion of work. This mode instantaneously sense cloth quality and requirement of water, water temperature, detergent, load, wash cycle time and perform operation accordingly.
ii) Semi Automatic Mode: In this semiautomatic mode in which washing conditions are predefined. Once the predefined mode is started the system perform its job and after completion it inform the user about the completion of work.
iii) Manual Mode: In this mode, user has to specify which operation he wants to do and has to provide related information to the control system. For example, if user wants to wash clothes only, he has to choose ‘wash’ option manually. Then the system ask the user to enter the wash time, amount of water and the load. After these data are
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system should inform the user.
Remember that Modes should be a selectable by a keypad.
A washing machine may have a System Controller (Brain of the System) which provides the power control for various monitors and pumps and even controls the display that tells us how the wash cycles are proceeding. A washing machine comprise several components as shown in Figure 3.
Figure 3: Block Diagram of Washing Machine
The working of these components is as follows:
i) Display Panel: It is a touch panel screen to control all the operations of a machine
ii) Sensor: It measures the water level and appropriate amount of soap. Input devices for automatic washing machine are sensors for water flow, water level and temperature; door switch; selector knob or buttons for settings such as spin speed, temperature, load size and types of wash cycle required.
Water Level Sensor: It indicates beep sound when water level is low in washing tub.
Door Sensor: It indicates beep sound when all clothes are washed that means now you can open the maching door and also you can move to your next phase. Next phase will be dry Phase. This phase also follows same concept for drying the clothes.
iii) Driving Motor: Motor can rotate in two directions either “reverse’ or ‘forward’. The forward direction drives the current in forward direction and motor rotates forward. The reverse direction driver does the opposite of it. A washing machine can maintain single motor in fully automatic or double motor in semi automatic washing machine.
Sequence of washing the clothes with this can be explained in few steps as follows:
1) Put on your dirty clothes on to the wash tub for washing 2) Put the detergent Soap (of your choice like Surf n Excel etc.)
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Display panel
System Controller
Sensor
Driving Motor
Water Pump
Inverter Unit
Fundamentals of Embedded Systems 3) Put ON the tap, water rushes inside the tub.
4) If its electronic control , then by the press of the keys ,you could program , if its mechanical it shall something like an mechanical switches wherein you are allowed to operate for setting the wash time.
5) Now the wash motor rotates and washes the clothes and gives you a beep sound
6) Now your clothes are washed …remove it from the wash tub and put it on the spin tub and program it accordingly…after spinning clothes are dried and you are allowed to hang it for proper drying in sunlight.
The fully automatic also comes in two category front loading as well as top loading.
i) Front loading is the one wherein you are given an opening to put clothes in on the front side.
ii) Top loading is on the top.
iv) System Controller: Such Component is used to control the motor speed. Motor can move in forward direction as well as reverse direction.
System Controller reads the speed of motor and controls the speed of motor in different phases such as in Washing, Cleaning Drying etc. All kinds of Sensors such as Door Sensor, Pressure Sensor and Keypad, Speed sensor are also maintained by this.
v) Water Pump: The water pump is used to recirculate water and drain out the
dirty water. This pump actually contains two separate pumps inside one: The
bottom half of the pump is hooked up to the drain line, while the top half
recirculates the wash water. The motor that drives the pump can reverse direction.
It spins one way when the washer is running a wash cycle and recirculates the
water; and it spins the other way when the washer is doing a spin cycle and
draining the water
1.6.2 Digital Sound Recorder
A digital sound recorder is a consumer electronic appliance designed to record and
play back speech. The messages are recorded using a builtin microphone and they are
stored in a digital memory. The user can quickly play back any message at any
moment through a speaker placed in the front of the device.
Figure 4 shows what our sound recorder could look like. It is a hand held unit with flat display and fairly large buttons.
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Figure 4: Block Diagram of Digital Sound Recorder
The main features of the digital sound recorder are:
• Easy to use with on screen menus.
• Direct access to any message.
• Alarm clock with year2000ready calendar. The user can set a daily alarm. The alarm beeps until the user presses a key, or after 60 seconds.
• Full Function LCD Display. The current date and time is always shown in thedisplay. The display also shows clear directions about how to use it and what it is doing.
• Batterylevel indicator. The system beeps when the battery is low.
• Standby mode. It economizes the battery power. The system switches off theperipherals when they are not in use. The normal operation is resumed when the user presses a key.
Such a system provides good sound quality. And also sound is processed at 6 KHz using eight bits per sample.
In Digital Sound Recorder system there are six different Functions:
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Screen
Yes No
Functions of Digital Sound Recorder System
Recording
Playback
Delete Set AlarmSet Clock Watch Time
Fundamentals of Embedded Systems
1) Record a message
When we want to record a message then we will use following steps:Step1: Selects a message slot from the message directory Step2: presse the ‘record’button. If the message slot already stores a message, it is deleted. The system starts recording the sound from the microphone until the user presses the ‘stop’ button, or the memory is full.
2) Playback a message
When we want to playback a message Then we will use following steps:Step1: Selects a recorded message slot Step2: and then presses the ‘play’ button. If the message slot contains a recorded message then it is played through the speaker until its end or until the user presses the stop button.
3) Delete a message
When we want to delete a message Then we will use following steps:Step1: The user selects a used message slotStep2: and then presses the ‘delete’ button. The message is permanently deleted from the memory and its memory space is freed up.
4) Set the alarm time
When we want to Set the alarm state, Then the user can switch on and off the alarm and set the time when the alarm will sound.This is done by selecting the different options of the alarm menu.
5) Set the clock time
When we want to set the clock time message Then user can set the clock time and adjust it to the current time zone.
6) Watch the time
The system constantly shows the current time and date on the display. The user justlooks at it.
F Check Your Progress 1
1) Distinguish between Embedded Systems and Non Embedded Systems.……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
2) Explain the characteristics of real time operating system for embedded system applications.………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
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………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
1.7 SUMMARY
Embedded system is a kind of computer system or computing device that performs a dedicated function and/or is intended for use with a specific embedded software application. It has been found that such systems are not usable as a commercially viable substitute for generalpurpose computers. In the same way, we can define embedded operating system as the software program that manages all the other programs in an embedded device after initial load of programs.
Important concepts like requirement and specifications play a vital role in Embedded System design implementation. Such Systems use programming languages in which hardware languages such as Verilog and VHDL are used for their hardware support and also well known software languages like C, C++ and Java etc. We have also discussed various applications of Embedded System in section.
1.8 ANSWERS/SOLUTIONS
1) An embedded system is a singlepurpose computer built into a larger system for the purposes of controlling and monitoring the system. These are also known as special purpose computer system. Example: Digital watches and MP4 Players, Digital Sound Recorder.
Non Embedded Systems are also known as general Computer general purpose computer (e.g. a personal computer) is defined not to be an embedded system. Such system can do many tasks depending on programming. Example: Handheld devices. share some elements with embedded systems — such as the operating systems and microprocessors which power them — but are not truly embedded systems, because they allow different applications to be loaded and peripherals to be connected.
2) RTOS Characteristics for Embedded Systems Applications:
• They have limited memory that is modular kernels. Modular kernels means only include the needed services.
• The executed processes are usually known at system design. RTOS often linked with the executed application(s) to the instruction memory.
3) The advantages using Verilog HDL are:
I) Easy to writeII) Easy to understand as it similar to C programIII) Easier to learn compared with VHDL.
1.9 FURTHER READINGS
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Fundamentals of Embedded Systems1) Raj Kamal, “Embedded Systems”, Tata Mcgraw Hill.
2) Steve Health, “Embedded Systems Design”, EDN 2nd Ed.
Reference Websites:
i) http://en.wikipedia.org/wiki/Embedded_systemii) http://en.wikipedia.org/wiki/Embedded_operating_system
iii) http://wapedia.mobi/en/Embedded_systemiv) http://www.learnc.com
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