ANNA UNIVERSITY OF TECHNOLOGY – COIMBATORE

B.E. (Electronics and Communication Engg.)

VII Semester

R2008 Regulation

EMBEDDED SYSTEMS

(2 Marks - Question Bank)

Prepared By

Prof. N.SHANMUGASUNDARAM

Professor & Head, Department of ECE,

VIDYAA VIKAS COLLEGE OF ENGINEERING AND TECHNOLOGY, TRICHENGODE, NAMAKKAL DISTRICT

TAMIL NADU - 637214.

Email: raja_ns@rediffmail.com

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EMBEDDED SYSTEMS

UNIT I ARCHITECTURE OF EMBEDDED SYSTEMS 9

Categories of Embedded Systems-Specifications of Embedded systems-Resent trends in Embedded

Systems-Hardware Architecture-Software Architecture-Communication software-Process of

generation of executable image-development/testing tools.

UNIT II PROGRAMMING FOR EMBEDDED SYSTEMS 9

Getting the most of C-data types-manipulating bits in memory and I/O ports-accessing memory

mapped I/O devices – structures-variant access-mixing C to assembly-register usage-use of

addressing options-instruction sequencing – procedure call and return-parameter passing –

retrieving parameters memory management-scope-automatic allocation-static allocation-dynamic

allocation shared memory-recognizing shared objects-reentrant functions-accessing shared

memory device drivers- productivity tools.

UNIT III HARDWARE PLATFORM 9

PIC microcontroller- Architecture of PIC 16c6x/7x- FSR- Reset action- Oscillatory connection-

Memory organization- Instructions- Addressing modes- I/O ports- Interrupts-Timers- ADC-

Assembly language programming.

UNIT IV REAL-TIME OPERATING SYSTEM CONCEPTS 9

Architecture of the Kernel-task and task scheduler-Interrupt Service Routines- Semaphores-Mutex-

Mailboxes-Message Queues-Event Registers-Pipes-Signals-Timers-Memory Management – Priority

Inversion Problem

UNIT V REAL-TIME OPERATING SYSTEM TOOLS AND CASE STUDIES 9

Use of µC/OS-II- Case study of coding for an Automatic Chocolate Vending Machine using MUCOS

RTOS- Case study of an Embedded system for an Adaptive Cruise Control Systems in a Car- Case

study of an Embedded Systems for a Smart Card.

TOTAL: 45 TUTORIAL : 15

TEXT BOOKS:

1. K.V.K.K.Prasad “Embedded /Real-Time Systems: Concepts, Design and Programming” Dream tech, 2003.

2. Ajay V Deshmukh “Microcontroller Theory and Applications” Tata McGraw Hill 2005

REFERENCES:

3. Raj Kamal “Embedded Systems Architecture Programming and Design” 2/e TMH, 2008

4. David E Simon “An Embedded Software Primer” Pearson Education 2003

5. Daniel 5.W Lewis, “Fundamentals of Embedded Software” Pearson Education- 2001

6. Peatman “Designing with PIC Micro Controller”, Pearson 2003

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UNIT I

ARCHITECTURE OF EMBEDDED SYSTEMS

1. Define Embedded System.

An embedded system is one that has computer hardware with software embedded on it and

designed for a specific task.

An embedded system can be defined as a computing device that does a specific focused job.

Applications such as the air conditioner, VCD player, printer, fax machine, etc. are some of the

examples of embedded system.

Each of these applications will have a processor and special hardware to meet the specific

requirement of the application along with embedded software that is executed by the

processor for meeting that specific requirement.

2. List application areas of Embedded Systems.

Various application areas of embedded systems are...

� Consumer appliances

� Office automation

� Industrial automation

� Medical electronics

� Computer networking

� Telecommunication

� Wireless technologies

� Instrumentation

� Security

� Finance

3. What are the different categories of embedded system?

Based on the functionality and performance requirements, embedded systems can be

categorized as

� Stand-alone embedded systems. Eg. AC, Oven, CD player, TV.

� Real-time systems. Eg. Aircraft control, Missile & Satellite control

� Networked Information appliances. Eg. Weather monitoring system

� Mobile Devices. Eg. PDAs, Smart phones.

4. What are the classifications of Embedded system?

Based on complexity of hardware and software, size and capability, the embedded systems are

classified as follows.

� Small scale Embedded System

� Medium scale Embedded System

� Sophisticated Embedded System.

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5. Give examples for Small, Medium & sophisticated scale embedded systems.

Small Scale Embedded System

� Automatic chocolate vending machine

� Stepper motor controller for a robotics system

� Washing or cooking system

� Multitasking toys

Medium Scale Embedded System

� Computer Networking Systems

� Entertainment systems

� Embedded firewall / Router

� Signal tracking system

Sophisticated Scale Embedded System

� Embedded system s for wireless LAN & for convergent technology devices.

� Security products & high speed network security, gigabit rate encryption rate

products

� Embedded system for real time video & speech

6. List the specialties of embedded systems.

As compared to desktop computers, workstations or mainframes, embedded systems have

many specialties. Developers need to keep these specialties in mind while designing

embedded systems. They are,

� Reliability

� Performance

� Power consumption

� Cost

� Size

� Limited user interface

� Software upgradation capability

7. List the factors to be considered while evaluating the processor for embedded system.

� Clock Speed

� Width and Number of Registers

� Width of Data and Address bus

� Internal RAM & ROM

� Interrupt lines

� On-chip peripherals such as Timers, UART, ADC, DAC, etc.

8. What are the hardware components of embedded systems?

� Processor

� Memory

� Timers & Interrupt Controller

� Serial/Parallel Ports

� Input devices, Interfacing/Driver circuits

� Output Interfacing/Driver circuits

� Power supply, Reset & Oscillator circuits.

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9. Define processor.

A processor is a IC, which is capable of performing an arithmetic or logical operation on a given

data as per the command given to it.

10. Compare CISC and RISC processor.

CISC: Complex Instruction Set Computer (CISC)

Aim of designing CISC processor is to reduce the software complexity by

increasing the complexity of the processor architecture. CISC has large no of

instructions. With less instructions, a task can be performed and hence, the

memory requirement in less. No. of registers are available in CISC processor is

very less.

Eg. Intel x86 family and Motorola 68000 series processors.

RISC: Reduced Instruction Set Computer (RISC)

RISC has limited no. of instructions and hence, complex operation is carried out

through sequence of more simple instructions. Large number of registers is

required in RISC processor. Another important feature of RISC processor is

pipelined instruction execution.

Embedded systems generally use RISC processor.

Eg. ARM, ATMEL, AVR, MIPS, Microchip’s PIC family processors, Power PC and

Sun SPARC processor.

11. What are the three processor architectures in embedded systems?

Von-Neuman Architecture:

This architecture has common memory for both data and program codes.

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Harvard Architecture:

In this architecture, there are separate memories blocks, one is program memory and the

other is data memory. Program memory stores only instructions and data memory stores

only data. Two pairs of data buses are used between CPU and the memory blocks.

Super Harvard Architecture:

The super Harvard architecture (SHARC) is a slight, but significant modification of the

Harvard architecture. In Harvard architecture, the data memory is accessed more

frequently than the program memory. Therefore, in SHARC, provision has been made to

store some secondary data in the program memory to balance the load on both memory

blocks.

12. What is Microcontroller?

A microcontroller is a single IC with a processor and several other on-chip peripherals such as

RAM, ROM, Comm. Ports, TIMERS, ADC/DAC, etc.

Compact size of microcontroller suits the requirements for embedded systems and hence

widely used in most of the embedded applications.

13. What are the functional blocks of a microcontroller?

The functional circuits of a microcontroller are,

� Processor

� internal RAM for Data & stack

� Timers & Watchdog timer

� ROM / PROM / EPROM

� External Memories Interfaces

� I/O Ports Control & Interfaces / Drivers

� Serial UART communication port

14. What are the features of DSP?

A DSP provides fast, discrete-time, signal processing instructions. It has very large instruction

word (VLIW) processing capabilities, it processes Single Instruction Multiple Data (SIMD)

instructions fast, and it processes Discrete Cosine Transformations (DCTs) and inverse DCTs

(IDTs) fast.

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15. What is GPP & ASIP?

GPP: A processor from a number of families of processors, microcontroller, embedded

processors and DSPs having a general purpose instruction set and readily available compilers

to enable programming in a high level language is called a General Purpose Processor (GPP).

ASIP: A processor designed for specific application on a VLSI chip is called an Application

Specific Instruction Processor.

16. What is ASSP?

Application Specific System Processor is a processing unit for specific tasks, foe e.g. Image

compression and that is integrated through the buses with the main processor in an

embedded system.

17. What is System-On-Chip?

A complete system on a single VLSI chip that comprises of all needed analog as well as digital

circuits in it. For example, mobile phone.

18. What are the various forms of system memories?

� Internal RAM

� Internal ROM / PROM /EPROM

� External RAM

� External ROM / PROM

� Internal & External Caches

� Hybrid memory such as E2PROM, NV-RAM or flash memory

19. List the important sensors and transducers.

� Temperature Sensors. Eg. AD22100, AD22103, DS18B20

� Light Sensors. Eg. TAOS TSL250R

� Accelerometers. Eg. ADXL 150/250

� Pressure Sensors. Eg. MPXA 6115A

� Microphone and Speakers

� Video camera and Monitor

20. List the important types of Displays.

� Light Emitting Diode (LED)

� Liquid Crystal Display (LCD)

� Thin Film Transistor (TFT) Display

� Organic Light Emitting Diode (OLED)

21. List the important Serial communication protocols.

� Inter-integrated Circuit (I2C)

� Serial Peripheral Interface (SPI)

� Universal Serial Bus (USB)

� Controller Area Network (CAN)

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22. List the important communication interfaces used in embedded systems.

� Serial interface using RS232

� Serial interface using RS422/RS485

� Universal Serial Bus (USB)

� Infrared

� Ethernet

� Wireless interface using IEEE 802.11 (WLAN)

� Bluetooth

� ZigBee IEEE 802.15.4

23. Define interrupt handler.

It is a unit that handles the processor operations arising out of an interrupt from a source.

24. What is watchdog timer?

It is a timer which resets the processor in case the program gets struck for an unexpected

time, with the help of timeout signal.

25. What is reset circuit and power-up reset?

The reset circuit activates for a fixed period and then deactivates. It helps the processor to

start the processing of instructions from a starting address.

Power-up reset vector also provides a starting address which is different from that provided

by a reset circuit.

26. What are the different categories of embedded operating system?

Operating system used in embedded system can be broadly divided into the following

categories

� Non-real-time embedded operating system

� Real-time operating system

� Mobile/handheld operating system

27. List the different categories of OS.

� Single-tasking OS (MS-DOS)

Multi-tasking OS (WINSOWS XP)

� Single-user OS (MS-DOS)

Multi-user OS (UNIX)

� Command-driven OS (MS-DOS)

GUI-based OS (WINDOWS XP)

28. List the functions of OS.

� Task management

� Memory management

� I/O management

� Providing service to applications

� Providing proper user interface that hides underlying hardware

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29. What is Kernel?

Kernel is a program with functions for memory allocation and deallocation, task scheduling,

inter process communication, effective management of shared memory access by using the

signals, exception handling signals, Semaphores, queues, mailboxes etc.

30. Define RTOS.

Real Time Operating System is software for real-time programming, scheduling of tasks,

management of resources like memory, devices, etc. to meet time deadlines in embedded

systems.

31. List the special requirements in RTOS for embedded systems.

� Reliability

� Multi-tasking with time constraints

� Interrupt Latency control

� Small footprint

� Support diskless systems

� Portability

� Scalability

� Support for standard API

32. What is ROM image?

The final stage software is also called ROM image, because just as an image is a unique

sequence and arrangement of pixels, embedded software is also a unique placement and

arrangement of bytes for instructions and data.

33. What are the steps required for converting assembly language into a ROM image?

� Assembler

� Linker

� Loader

� Locator & Device Programmer

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34. What is the use of code optimizer?

Code optimizer is used in the conversion of high level language into a ROM image for

optimizing the code before linking.

35. What is Compiler?

Compiler is a software tool that converts a high level program (written using programming

languages like C, C++, Java, and so on) into an object code.

36. What is Assembler?

Assembler is a software tool that converts an assembly program (written using mnemonics

of a processor, i.e., instruction set of a specific processor) into an object code.

37. What is meant by context switching?

The mechanism of storing the current status of CPU registers in a stack to run other task is

known as context switching.

38. What is meant by Inter-task communication?

Tasks may need to exchange data among themselves to synchronize the tasks in an

application. This is known as Inter-task communication. The techniques used for ITC are

Signals, Semaphores, Mailboxes, Queues, Pipes and Event flags.

39. What is meant by cross platform development?

The process of developing machine codes for a specific processor of an embedded system

from a high level / assembly level program written on a PC (with different processor) using

various software tools is called cross platform development.

40. List the various hardware development / testing tools.

Digital Multimeter : Measures current, voltage, continuity of connections

Logic Analyzer : Checks the timing of the signals

Oscilloscope : Analyze the waveforms in time domain

Spectrum Analyzer : Analyze the waveforms in frequency domain

41. List the various software development / testing tools.

� OS Development Suite

� Cross-platform Development tools (IDE)

� ROM Emulator

� EPROM Programmer

� Instruction Set Simulator (ISS)

� In-Circuit Emulator (ICE)

42. List the possible boot sequences of an embedded system.

� Execute from ROM using RAM for data

� Execute from RAM after loading the image from RAM

� Execute from RAM after downloading from the host

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43. What is meant by Debug port?

Debugging a processor based board is very difficult. Hence, manufacturers provide a

standardized interface for debugging. JTAG (Joint Test Access Group) port is a mechanism

provided to debug the embedded system hardware and also for downloading the software

onto the embedded system board.

44. List out the layers of TCP/IP protocol suite.

The TCP/IP protocol suit consist of 5 layer

� Application layer

� Transport layer

� Internet protocol (IP) layer

� Data link layer(referred also as network layer)

� Physical layer

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UNIT II

PROGRAMMING FOR EMBEDDED SYSTEMS

1. What are advantages of writing embedded software in Assembly Language?

� It gives a precise control of the processor internal devices.

� The machine codes are compact.

� Device driver codes may need only a few assembly instructions

2. What are advantages of writing embedded software in C Language?

� The development cycle is short for complex systems.

� Type checking makes the program less prone to error.

� Control Structures make the program-flow path design tasks simple.

� Portability.

3. What is embedded C++?

Embedded C++ is a version of C++ that provides for a selective disabling which is the

disadvantage in C++. So, there is a less run-time overhead and less run-time library.

4. How can optimization be used to eliminate the disadvantages in embedded C++ programs?

Optimization can be used as follows.

� Declare private as many classes as possible.

� Use of char, int and boolean in place of the objects as arguments

� Use local variables as much as feasible.

� Recover memory already used by changing the reference to an object to NULL.

5. What is the use of type checking?

Type checking makes the program less prone to error.

For e.g. It does not allow subtraction, multiplication and division on the ‘char’ data types.

6. Define Configuration files.

Configuration files are the files for the configuration of the system. Device configuration

codes can be put in a file of basic variables and included when needed.

7. What is difference between function and macro-function?

A macro function is a collection of codes that is defined in a program by a name. It differs

from a function in the sense that once a macro is defined by a name, the compiler puts the

corresponding codes for it at every place where that macro name appears. But the codes for

a function are compiled once only.

8. What is recursive and reentrant function?

Recursive Function:

It is a function that calls itself. It must be a reentrant function also. Most often its use is

avoided in embedded systems due to memory constraints.

Reentrant Function:

It is a function that is usable by the several tasks and routines at the same time. All its

argument values are retrievable from the stack.

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9. What is the use of modifier register?

When a modifier register is inside a function block, a CPU register is temporarily allocated

when needed. There is no ROM or RAM allocation.

10. Define Queue.

It is a data structure into which elements can be sequentially inserted and retrieved in a FIFO

mode. It needs two pointers, one for the queue tail for insertion and other for the queue

head for deletion.

11. Define Stack.

A stack is a data structure in which elements can be pushed in or pulled out. It works on the

principle of Last-In-First-Out (LIFO).

12. How interrupts are handled in Queue?

Queuing of pointers to the function on interrupts and later on calling the functions from this

queue is a better approach as it provides the use of short execution time interrupt-service

routines.

13. Explain briefly stack overhead.

The repeated call to recursive function may cause the stack to full. This leads to insufficient

memory. Hence the stack overhead may occur which is primarily due to overflow of the

stack.

14. What is meant by inline assembly?

Inserting the assembly language codes in between the high-level language codes are called

inline assembly. It gives the benefits of processor specific instructions and addressing modes.

15. What is Optimization of memory?

When codes are made compact and fitted in small memory without affecting the code

performance, it is called memory optimization.

16. Define scalar data types?

The character, integer, unsigned integer, floating point number, long and double are called

scalar data types. Unlike an array data consists of one single element.

17. Give some examples for reference data types.

Arrays and strings are examples of reference data types.

18. What is meant by platform independence?

A code that can port on different machine and different operating systems is said to be

platform independent code.

19. What are preprocessor directives?

It is the program statements and directives for the compiler before the main function to

define global variable, global macro, new data type and global constants.

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20. What are the differences between including a header file and a text file or data file?

The differences between including a header file and a text file or data file are,

� The header files are well tested and debugged modules.

� They provide access to standard libraries.

� The header file can include several text file or C files.

A text file is description of the text that contains specific information.

21. List the Integer data types available in C programming language.

Data type Size Range

unsigned

Char

Short int

Int

Long int

8 bits

16 bits

16/32 bits

32 bits

0 to 255

0 to 65,535

same as unsigned short / long int

0 to 4,294,967,295

signed

Char

Short int

Int

Long int

8 bits

16 bits

16/32 bits

32 bits

-128 to +127

-32768 to +32767

same as unsigned short / long int

-2,147,483,648 to +2,147,483,647

22. Why TYPEDEFS are used in embedded system programming?

C’s primitive data type “char” may default to either signed or unsigned, and its primitive data

type “int” may have size of 16 or 32 bits. In most of the embedded applications, it’s

imperative to know the number of bits and range of most variables.

Hence, to avoid C’s ambiguity, derived data types are formed using TYPEDEFS and placed in a

text file (Eg. typedefs.h) and included in every source code file that uses them.

23. What are the two types of data conversions?

PROMOTION: A conversion is called a promotion, when there is no potential loss of accuracy

as when assigning an integer value to a floating point variable.

DEMOTION: It is the conversion which causes a loss of accuracy, when a floating point

variable is assigned to an integer variable, or when a 32-bit integer value is assigned to a 8-

bit char. Demotion usually make the compiler to issue a warning.

24. List the Boolean and Bitwise operators.

Operation Boolean

Operator

Bitwise

Operator

AND

OR

XOR

NOT

&&

||

(Not supported)

!

&

|

^

~

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25. Find the result of the following expression?

a) Boolean: (5 || !3) && 6 Ans:= (True OR (NOT True)) AND True

= (True OR False) AND True

= (True) AND True

= True

= 1

b) Bitwise: (5 | !3) & 6 Ans:= (00000101 OR !(00000011)) AND 00000110

= (00000101 OR 11111100) AND 00000110

= (11111101) AND 00000110

= 00000100

= 4

26. List the bitwise operations performed on data bits.

� Testing bits

� Setting bits

� Clearing bits

� Inverting bits

� Extracting bits

� Inserting bits

27. What is the significance of Pointers in C programming?

A Pointer in C is a variable that contains an address of a variable. This helps to access the

data of a variable faster in memory and in particular for array types of data.

Eg. Int A, *B, C ; A & C are normal variable and B is a Pointer variable

A = 10 ; Variable A is assigned with a value, 10

B = &A ; Variable B is assigned the address of variable A

C = *B ; Variable C is now assigned the content at address

stored in variable B

28. What is an Array?

An Array is an aggregate data type composed of several members of same data type.

The consecutive locations in memory are allocated for an array. The starting address of the

array (i.e., a[0]) is called Base address.

Eg. Int a[5];

a[0] a[1] a[2] a[3] a[4]

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29. Explain about manipulating bits in memory.

30. How testing a bit is made?

31. How setting a bit is made?

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32. How clearing of a bit is made?

33. How inverting a bit is made?

34. How to extracting of a bit is made?

35. How to replacing of a bit is made?

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36. What is a structure?

A Structure is a aggregate data type composed of several distinct members. A single

structure variable can contain member elements that represent a mix of chars, ints, doubles,

etc.

Structure declaration in C program struct PERSON

{

Int age;

Char gender;

};

Structure variable declaration struct PERSON sue;

(or)

PERSON sue;

Initialization of

structure variable members sue.age = 25;

sue.gender = ‘F’;

(or)

PERSON sue = {25, ‘F’};

37. What is meant by packed structures?

Structures are always stored in memory with their member components in the same order

as they appear in the structure description and there is no requirement that the components

be contiguous.

Struct {char c;

Int I;} x;

Sometimes, we need to use structures to describe a layout in which all the data is

contiguous. Thus, packed structures are a layout of data in memory in which the padding of

zeros is disabled.

Struct {char c;

Int I;

} x __attribute__ ((packed));

padding padding padding x.c

x.i

x.c

x.i

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38. What are Bit fields?

Bit fields in structures allow us to access the data using cleaner syntax that hides all the

necessary bit manipulation.

Illustration of declaring structure bit fields

Describing of time as structure in which the hours, minutes and seconds are declared as

structure bit fields.

typedef struct {

WORD16 seconds : 6,

minutes : 5,

hours : 5;

} TIME time1;

Time of 13:34:18 can be initialized into the packed representation time1 using simple

reference operator as follows,

time1.hours = 13;

time1.minutes = 34;

time1.seconds = 18/2;

39. What is a Union?

Union is an aggregate data type in which the members of it share a common memory space.

typedef union {

unsigned long int real;

FIXED32PARTS part;

} FIXED32REAL result;

31 16 15 0

result.part.whole result.part.fract

�--------------------------- result.real ----------------------------�

40. Explain the process of Assembler.

The translation of assembly-language source code into binary object code is a two-step

process in assembler. The assembler makes two complete passes over the source code of the

program.

During the first pass; the assembler builds a symbol table that contains the information

about programmer–defined identifiers, such as the labels attached to instructions and the

names of variables stored in memory.

During the second pass; the assembler uses this information to construct the representation

of the individual instructions.

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41. List the instructions in C that transfers the program control to another part of memory.

In C language, unconditional jumps are created by break, continue, switch and goto

statements and at the end of loops.

42. Explain the importance of String instructions.

There are some common loop operations that can be implemented using the Intel string

instructions for ultimate speed.

For example, string instructions can be used to initialize a region of memory to a constant

value, scan a region of memory for a particular value, copy one region of memory to

another, or compare the contents of two regions of memory.

43. List the Intel conditional JUMP instructions.

For comparing unsigned operands

JA/JNBE - Jump if above / jump if not below or equal

JAE/JNB - Jump if above or equal / jump if not below

JBE/JNA - Jump if below or equal / jump if not above

JB/JNAE - Jump if below / jump if not above or equal

For comparing signed operands

JG/JNLE - Jump if Greater / jump if not less or equal

JGE/JNL - Jump if Greater or equal / jump if not less

JLE/JNG - Jump if less or equal / jump if not greater

JL/JNGE - Jump if less / jump if not greater or equal

For equality comparisons

JE/JZ - Jump if equal / jump if zero (ZF=1)

JNE/JNZ - Jump if not equal / jump if not zero (ZF=0)

Other JUMP instructions

JC - Jump if CF=1

JNC - Jump if CF=0

JS - Jump if SF=1

JNS - Jump if SF=0

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44. List the attributes of Objects stored in memory.

Type - char, int, unsigned int, etc.

Name - The identifier used to access the object

Value - The data held within the object

Address- The address in memory where the object resides

Scope - That part of the source code where the object’s name is recognized

Lifetime- The notion of when the object is created and destroyed,

and thus, when it is available for use.

45. What is meant by scope in memory management?

Scope of a variable is based on the place of declaration in the program. It is either declared

(1) outside of all functions to create global variables or (2) immediately following a function

header to create temporary variables local to the function.

46. List the types of Memory allocation available in C.

Method Object is

created Object is initialized Object is destroyed

Automatic

Each time the program

enters

the function in

which it is declared

If specified in the

declaration,

initialization occurs each

time the program enters

the block

Each time the function

returns

Static

Once:

When the program is

first loaded into the

memory

Once:

Just before

the program

starts to run

Once:

When the

program stops

Dynamic

By calling the library

function

malloc()

By writing executable

statements that modify

its content

By calling the library

function

free()

47. What is meant by shared memory?

When two or more asynchronous (no predictable time relationship) instruction sequences

access the same data, that data is called shared memory. Access to shared memory must be

carefully coordinated or else data corruption may occur.

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48. What is meant by shared functions?

A shared function in one that is called by more than one thread; any function called by a

shared function is also a shared function. Any static object referenced within a shared

function is thus form of shared memory.

Since there is only a single instance of the object, its content is inherently shared by all

threads that call a function that references it.

49. Explain the type qualifier “const”.

The keyword const is used to declare so that an object’s value may not be modified by the

program, i.e., that its value is read only. The declaration of a const object must include an

initial value, since no subsequent attempt to set its valued is allowed.

50. Explain the type qualifier “Volatile”.

The keyword volatile may be attached as qualifier on the declaration of an object in C to

indicate that its value may be asynchronously modified by mechanism other than the code in

which the declaration appears, such as DMA or ISR.

51. What is meant by Life Time of a variable?

52. What is Fragmentation?

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UNIT III

HARDWARE PLATFORM

1. In what way is PIC microcontroller different from 8051?

Most PIC microcontrollers are RISC based processors with Harvard architecture, where as

8051 is based on Von-Neuman architecture. Harvard architecture makes use of separate

program and data memories. PIC microcontroller has different data size for program and

data memory and hence it is difficult to use external memory for PIC microcontroller.

2. List the features of PIC 16C6x/7x.

� PIC microcontroller is designed in Harvard Architecture

� Separate memory for program and data

� Program memory: has 13-bit address & 14-bit data bus

� Data memory: has 8-bit address & 8-bit data bus

� 13-bit program counter

� Pipelined architecture for fast execution speed

� Has inbuilt ADC and Watch-dog timer

3. Compare features of other PIC microcontrollers.

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4. Draw the pin diagram of 16C61 and 16C71 microcontroller.

5. Describe the status register (Flag Reg) of PIC16C6X microcontroller.

STATUS register contains various flags and register bank select bits:

D7 D6 D5 D4 D3 D2 D1 D0

- - RPO TO PD Z DC C

RPO – Register bank select (to select 2 banks; one bit RPO is sufficient)

TO – Time-Out Bit (Reset status bit, is only readable)

PD – Power-Down Bit (Reset status bit, is only readable)

Z – Zero bit

DC – Digital-carry / Borrow bit

C – Carry / Borrow bit

6. State the power consumption of PIC microcontroller.

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7. What is meant by instruction pipelining?

PIC16C6x/7x family of microcontrollers use Harvard Architecture and instruction pipelining to

achieve exceptionally fast execution speed for a given clock rate. Through pipelining,

instruction fetch and execution are carried out simultaneously in a single cycle.

8. List the CPU registers of 16Cxx family microcontrollers.

9. What is PCL and PCLATH register?

PC, the program counter of PIC microcontroller is 13-bits wide and PCL is the lower byte of

the PC. PCLATH, stand for PC Latch and it holds the upper 5-bits of the program counter.

PCLATH is transferred into the PC when content is written into PCL.

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10. List the SFRs of PIC microcontroller.

The lower bytes of register bank are identified as Special Function Register (SFRs). The CPU

and peripheral modules use SFRs for controlling the operation of the device.

11. Describe the Register file structure in PIC microcontroller.

The term Register File is PIC terminology used to denote the locations that an instruction can

access via an address. The register file consists of two components.

1. General purpose register file

2. Special purpose register file

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The general purpose register file is another name given to RAM memory of PIC

microcontroller. The special purpose register file contains input and output ports as well as

the control registers used to establish each bit of a port as either an input or an output.

The register file structure is illustrated in figure below with addresses that span the 8-bit

range from ‘00’ to ‘FF’. Because the direct addressing mode employed by many instructions

use only 7-bit of the instruction to identify a register file address, the 8th bit of the register

file address must come from a separate register bank selection bit, RP0.

12. List and brief the addressing modes in PIC microcontroller.

Direct Addressing: It uses 7 bits of instruction and the 8thbit from RP0.

If RP0 bit is 0; then bank 0 is selected or otherwise bank 1 is selected.

Indirect addressing: In this mode; the 8-bit address of the location in register file to be

accessed is written in FSR and INDF register is used for indirect addressing.

13. What is FSR?

FSR stands for File Selection Register. FSR is the pointer used for indirect memory addressing

in the whole register file.

It must be noted that, in PIC, every instruction that can be used for direct addressing may

also be used in a different way for indirect addressing. The only difference in indirect

addressing mode is that one has to write the address byte in FSR and then use INDF in the

instruction. Thus, FSR points to the desired memory location.

14. List the reset action that takes place in PIC microcontroller.

PIC reset action takes place due to difference mechanism. Those are

• Power–on–reset (POR),

• MCLR reset during the normal operation,

• Master clear MCLR reset during SLEEP mode,

• Watch dog timer reset during normal operation,

• Brown–out–reset (BOR).

15. Explain the brown-out reset feature of PIC microcontroller.

PIC microcontroller can be reset automatically in running condition, due to the brown-out.

Brown-out reset takes place when the supply voltage falls below 4V. The device remains in

brown-out reset condition until the supply voltage is restored. PIC 16C61 and 16C71 does not

support this feature.

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16. Explain the structure of Watchdog timer in PIC microcontroller.

Watch-dog timer is a simple timer circuit that prevents the processor from endless loop

(hanging condition) and looks after the functioning of the system with respect to time. The

watch-dog timer will reset the PIC microcontroller when the ‘CLRDWT’ instruction is not

executed periodically.

CLRDWT instruction resets the TO bit in the status register. WDT timer can also be reset the

TO bit, when the CLRDWT is not executed periodically. The normal time-out period of PIC

microcontroller is around 18ms. The watch-dog timer is enabled at the time of device

programming and it cannot be turned off after programming.

17. Explain about Clock generation in PIC briefly.

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Alternate method of generating clock signal is by connecting quartz crystal to the PIC

microcontroller along with two start-up capacitors.

18. Short notes on I/O ports of PIC microcontroller

Port A: RA0 to RA4 (5 lines) (Address 05). RA4 has alternate function. TRISA (85H) is SFR used

to configure these lines individually as either inputs or outputs. Setting bit in TRIS will

configure as input and 0 will configure as output.

Port B: RB0 to RB7 (8 lines). TRISB It has weak internal pull up which is to be enabled. POR

disables pull-ups.

19. Explain about the interrupts in PIC

There are 3 Interrupt Sources for PIC16C6X.

External Interrupt: Due to external source. Edge Sensitive RB0/INT causes this interrupt. This

interrupt wakes up processor from SLEEP. This must be set before going into SLEEP mode.

Timer 0: Timer 0 overflows when timer count overflows from FF to 00.

Port B Change Interrupt: A change from high to low or low to high on port B pins RB4 to RB7

causes this interrupt. This interrupt can wake device from SLEEP.

20. Write short notes on Timers in PIC16C6X.

All PIC16C6X devices have three timer modules except for the PIC16C61, which has one timer

module.

The Timer0 module is a simple 8-bit overflow counter. The clock source can be either the

internal system clock (Fosc/4) or an external clock. When the clock source is an external

clock, the Timer0 module can be selected to increment on either the rising or falling edge.

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21. List out the types of instructions in PIC Microcontroller.

Each PIC16CXX instruction is a 14-bit word divided into an OPCODE which specifies the

instruction type and one or more operands which further specify the operation of the

instruction.

� Byte-oriented,

� Bit-oriented,

� Literal and control operations

22. Explain Byte-oriented instruction set.

Byte-oriented instructions, 'f' represents a file register designator and ‘d’ represents a

destination designator. The file register designator specifies which file register is to be used

by the instruction. The destination designator specifies where the result of the operation is

to be placed. If ‘d’ is zero, the result is placed in the W register. If ‘d’ is one, the result is

placed in the file register specified in the instruction.

23. Explain Bit-oriented instruction set.

Bit-oriented instructions, 'b' represents a bit field designator which selects the number of the

bit affected by the operation, while 'f' represents the number of the file in which the bit is

located.

24. Short note on literal and control operation instruction set.

Literal and control operations, 'k' represents an eight or eleven bit constant or literal value.

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25. Write short notes on INTCON register of PIC16C6x/7x controller.

INTCON is an Interrupt control register in PIC microcontrollers for controlling all interrupts.

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26. List the external interrupts & timers of PIC microcontroller.

The PIC microcontroller has one pin RB0/INT, which serves as its primary external interrupt

input. In addition to above, it has three timers TIMER0 TIMER1 & TIMER2 with CCP module.

27. List the features of ADC in PIC 16C6x/7x microcontroller.

PIC 16C7X supports analog inputs. PIC 16C71 microcontroller has four analog channels of 8-

bit ADC, with 20 µs of conversion time per channel. Four analog channels AIN0, AIN1, AIN2

and AIN3 are the alternate functions of Port_A pins RA0, RA1, RA2, and RA3 respectively.

ADCON0 controls the function of pins RA0 to RA3. This allows the configuring pins RA0-RA3

as analog or digital inputs.

29. What is sleep mode in PIC microcontroller?

PIC microcontroller supports a power saving ‘Sleep mode’. The clock may be frozen with all

the data preserved in the processor memory. A software command allows the processor to

enter into this mode. It will be in sleep mode until the PIC is reset again.

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30. Explain the operation of OPTION register.

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31. Instruction set of PIC microcontroller.

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32. Programming examples for PIC microcontroller.

A. Program to configure PORT_B using TRISB

B. Program to implement a Delay routine.

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C. Program to initialize PORT_A

D. Program to initialize PORT_B

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E. Program to alter PORT_B in response to external interrupt on pin RB0

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F. Program for A/D conversion.

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UNIT IV

REAL TIME OPERATING SYSTEMS CONCEPTS

1. Define RTOS.

It is an operating System for embedded system with real time task scheduling, interrupt-

latency control, synchronization of tasks with IPCs and predictable timing behavior of the

system.

2. Name some RTOS services.

(i) Basic OS functions

(ii) RTOS Main functions (Task Scheduling & interrupt latency control)

(iii) Time Management

(iv) Predictability

3. Compare OS and RTOS.

OS: On a PC, OS takes control of the PC as soon as it is turned on and then it lets the

application program to start. OS checks any pointer which passes into a system function for

its validity. OS consumes lot of memory space and it contains all in-built functions.

RTOS: Application program is linked to the RTOS. At boot-up, application usually gets control

first and then it starts RTOS. Many RTOS don not protect themselves and skip the checking

process for better performance. To save memory, RTOS has only the functions needed for an

application.

4. What is Round Robin or cyclic scheduling?

It is a scheduling algorithm in which the tasks are scheduled in sequence from a list of ready

tasks.

5. Explain briefly about Preemptive scheduling.

A scheduling algorithm in which a higher priority task is forced (Preempted) to block the low

priority task by the scheduler.

6. What is Time Slicing and Fixed real time scheduling?

Time Slicing Scheduling

It is a scheduling algorithm in which each task is allotted a time slice after which it is blocked

and waits for its turn on the next cycle.

Fixed Real Time Scheduling

It is a scheduling strategy in which the time for each task is fixed.

7. Explain briefly the term Task.

Task is a subroutine in an application that makes certain action to be performed. A Task that

has its independent program counter values and an independent stack. A single CPU system

runs one task at a time.

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8. What is Task State?

A state of a task changes on scheduler directions. A task at an instance can be in one of the

four states, idle, ready, blocked ad running that are controlled by the scheduler.

9. Explain Task scheduler.

It is part of a RTOS. It keeps track of the state of each task and decides which one task should

go into the running state. Scheduler in an RTOS looks at the priorities assigned to tasks, and

among the tasks that not in the blocked state, the one with highest priority is allowed to run

and the rest of them are made to wait in the ready state.

10. When a blocked task is allowed to run on a processor?

When a task is blocked, it never gets the processor. Therefore, an interrupt routine or some

another task in the system should signal that whatever the blocked task waiting for has

happened. Otherwise, the task will be blocked forever.

11. How does a scheduler know whether a task is blocked or not?

RTOS provides a collection of functions that tasks can tell a scheduler what events they wait

for and to signal that events have happened.

12. What happens if all the tasks are blocked?

If all the tasks are blocked, then the scheduler will spin in some tight loop somewhere inside

the RTOS, waiting for something to happen. If nothing ever happens, then it ends in an

infinite loop. Therefore care must be taken by programmer to invoke a interrupt routine that

call some RTOS function that unblocks a task.

13. What if two tasks with the same priority are ready?

There are two options in this situation. (1) RTOS should declare as illegal when two tasks are

assigned with same priority. (2) RTOS can time-slice between two tasks that has the same

priority.

14. List the rules to decide if a function is Re-entrant.

1. A reentrant function may not use variables in a non-atomic way unless they are stored

on the stack of the task that call the function or are otherwise the private variables of

that task.

2. A reentrant function may not call any other functions that are not themselves reentrant.

3. A reentrant function may not use the hardware in a non-atomic way.

15. Define Inter process communication (IPC).

An output from one task (or process) passed to another task through the scheduler and use

of signals, exceptions, semaphores, queues, mailboxes, pipes, sockets, and remote

procedure call is known as inter process communication.

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16. Define Semaphore.

Semaphore is a special variable or function that is used to take note of certain actions to

prevent another task or process from proceeding.

17. List the semaphore related problems.

� Forgetting to take the semaphore

� Forgetting to release the semaphore

� Taking the wrong semaphore

� Holding a semaphore too long

18. Explain Mutex, Counting and Resource Semaphore.

Mutex Semaphore

A special variable used to take note of certain actions to prevent any task or process from

proceeding further and at the same time let another task exclusively proceed further.

Counting Semaphore

Sometimes, a semaphore can be taken multiple times. A semaphore can be an integer which

can be incremented when released and decremented when taken. If a task tries to take a

semaphore when the integer value is equal to 0, then the task will be blocked. This is called

Counting semaphore.

Resource Semaphore

Sometimes RTOS allows a semaphore to be released only by the task that has taken them.

These semaphores are useful for shared data problem, but cannot be used for

communication between two tasks. Such semaphores are called as Resource semaphores.

19. What are the problems that may arise while using semaphores?

The problems that may while using semaphores are,

� Sharing of two semaphores creates a deadlock problem.

� Without a timeout an ISR worst-case latency may exceed the deadline.

� If a semaphore is not taken, and another task uses a shared variable.

� When using multiple semaphores, if an unintended task takes the semaphore, it

creates a problem.

� It may introduce priority inversion problem.

20. What is shared data problem?

If a variable is used in two different tasks and another task if interrupts without before the

operation on that variable is completed, then the shared data problem arises.

21. List the ways to protect the shared data.

� Disabling the interrupts

� Taking semaphores

� Disabling the task switches

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22. Explain briefly Deadly embrace situation.

Consider a situation in which two tasks (task1 and task2) are using two semaphores,

semaphore_A and semaphore_B. When task1 is run, it takes semaphore_A and before it

proceeds further and takes semaphore_B, RTOS switches to task2. Now task2 takes

semaphore_B and it waits for release of semaphore_A by task1. None of these tasks are able

to proceed further. This situation is called Deadly embrace.

23. What is priority inversion problem? How it can be solved?

A problem in which a low priority task unintentionally do not release the semaphore for a

higher priority task. This makes the high priority task to wait for low priority task to release

the semaphore. This is called Priority Inversion. This problem can be solved by temporarily

boosting the low priority task to higher priority task which is called as priority inheritance.

24. Explain the term (i) Message Queue (ii) Mailbox (iii) Pipe (iv) Socket.

Message Queue

RTOS allows a task to send multiple messages into a FIFO queue for use by another task(s)

using queue message as an input.

Mailbox

RTOS allows a certain no. of messages to be stored in each mailbox. Separate functions are

used to identify the appropriate mailbox, to add and read a message from the selected

mailbox.

Pipe

Pipes are like queues. RTOS can create them, write to them, read from them and so on.

Socket

It provides the logical link using a protocol between the tasks in a client-server or peer-to-

peer environment.

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25. List the pitfalls in using Mailbox, Message queues and Pipes.

� Most of the RTOS do not restrict which tasks can read from or write to any given queue,

mailbox or pipe. Therefore, programmer must ensure that tasks use the correct one each

time.

� RTOS cannot ensure that data written onto a queue, mailbox or a pipe will be properly

interpreted by the tasks that read it.

� Running out of space in queues, mailboxes or pipes is usually a disaster for embedded

software.

� Passing pointers from one task to another through a queue, mailbox or pipe is one of the

several ways to create shared data inadvertently.

26. What is Timer and counting devices?

A Timer gets the inputs from the internal clock of a processor or from system clock and

generates a required time delay.

Counting device is a unit for getting the count-inputs on the occurrence of events that may

be at irregular intervals.

27. What are the types of Timer?

There are two types of timer. They are,

� Hardware timer

� Software timer

28. What is Timer Overflow or Time-Out?

A state in which the number of count inputs exceeded the last acquirable value and on

reaching that state, an interrupt can be generated. This state is called Time-Out or Timer

Overflow.

29. What is the difference between hardware timer and software timer?

Hardware timer gets the inputs from the internal clock with the processor or system clock. A

device driver program programs it like any other physical device.

Software timer executes a program which increases or decreases a count variable on an

interrupt from a timer output or from a real-time clock interrupt.

30. What are the different states in a timer?

The different states in a timer are,

� Reset State

� Idle State

� Present State

� Overflow State

� Active or Blocked State

� Done State

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31. Is it necessary to have a hardware timer device in a system? How does it work?

Yes, it is necessary to have atleast one hardware timer device in a system.

It is used as a system clock. The hardware timer gets the input from a clock out signal from

the processor and activates the system clock as per the num ticks preset at the hardware

timer.

32. What is an Event?

An event is essentially a Boolean flag that tasks can set or reset and that other tasks can wait

for. Event invokes a interrupt routine that runs a waiting task.

33. Compare Semaphores, Events and Queues/Mailbox/Pipe.

Semaphores are usually the fastest and simplest methods. However, not much information

can be passed through a semaphore, which passes just a 1-bit message saying that it has

been released.

Events are a little more complicated than semaphores and take little more of processor time.

The advantage of events over semaphores is that a task can wait for any one of the several

events at the same time and it can wait for only one semaphore.

Queues (also mailboxes & pipes) allow sending a lot of information from one task to another.

The drawback of queues (also mailboxes and pipes) is that adding and reading a message is

more processor intensive and more prone to insert bugs while programming them.

34. How a block of data is passed using queue?

Passing a pointer to a buffer from one task to another through a queue is a common way to

pass a block of data.

35. Explain the problem in using malloc() and free() functions for memory management in RT

embedded systems.

In real time embedded systems, malloc() and free() are avoided because of their slow

response and unpredictable execution times. Instead, most of the RTOS offer fast and

predictable functions along with free fixed size buffers.

36. List the two rules that an interrupt routine must follow in RTOS environment that do not

apply to task codes.

Rule-1:

An interrupt routine must not call any RTOS function that might block the caller.

Rule-2:

An interrupt routine may not call any RTOS function that might cause the RTOS to switch

tasks unless the RTOS knows that an interrupt routine, and not a task is executing.

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UNIT V

REAL TIME OPERATING SYSTEMS TOOLS AND CASE STUDIES

1. Name the important RTOS used in embedded systems.

MUCOS, Vxworks, PSoS, RTX51, WinCE, RT Linux, Nucleus, Symbian are the important RTOS.

2. List the Main functions of RTOS.

(i) Handling of interrupts.

(ii) Task scheduling.

3. List the basic functions in an RTOS.

The basic functions in an RTOS are,

� Kernel (Task Scheduler)

� Error handling functions

� System level functions

� System clock functions

� Time and delay functions

� Task state switch functions

� ISR functions

� Memory related functions

� IPC functions.

4. List the need for well tested & debugged RTOS.

When designing a complex embedded system, one needs the thoroughly tested bug free

codes for the following software components.

� Multiple task functions in Embedded C or C++

� Real time clock based software timers employing system clock

� Software for cooperative scheduler to maintain time deadlines

� If cooperative scheduler is not suitable, then software for Pre-emptive scheduler

� Device drivers and device managers

� Functions for IPC

� Networking functions

� Error handling and Exception handling functions

� Testing and system debugging software

A readily available, well tested and debugged RTOS thus not only simplifies the coding

process greatly for a developer, but also helps in building a product fast; it aids in building

robust and bug free software by thorough testing and simulation before locating the codes

into the hardware.

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5. Explain µC/OS-II (MUCOS) RTOS.

� µC/OS-II is a freeware RTOS, developed by Jean J. Labrosse in 1992.

� µC/OS-II is designed for non-commercial use.

� µC/OS-II is well documented for developer’s reference.

� µC/OS-II codes are written in C and in assembly language.

� µC/OS-II code ports on any processor that are used for embedded systems

6. What are the files associated with µC/OS-II RTOS?

The source files of µC/OS-II are categorized into two groups.

a) Processor dependent source file:

Two header files at the master are the following.

� os_cpu.h is the processor definitions header file

� os_cfg.h is the kernel building configuration file

Two C files for ISR and RTOS timer are os_tick.c and os_cpu_c.c

Assembly codes for task switching functions is os_cpu_a.s12

b) Processor independent source file:

Two files, MUCOS header and C files are ucos.ii.h and ucos.ii.c.

The C files for RTOS core, timer and task are os_core.c, os_time.c and os_task.c

The memory partitioning, semaphore, queue and mailbox codes are os_mem.c,

os_sem.c, os_q.c and os_mbox.c respectively.

7. List the features of µC/OS-II (MUCOS) RTOS.

The features of MUCOS are as follows.

� MUCOS operating system functions has a prefix of OS or OS_.

� MUCOS is a scalable OS.

� For multitasking, MUCOS employs pre-emptive scheduler.

� MUCOS has system level functions.

� MUCOS has task service functions.

� MUCOS has task delay functions.

� MUCOS has memory allocation functions.

� MUCOS has Inter-Process Communication (IPC) functions.

� MUCOS has semaphore functions.

� MUCOS has mailbox functions.

� MUCOS has queue functions.

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8. List the System level functions in MUCOS.

MUCOS support the following system level functions.

void OSInit (void) At the beginning prior to OSStart()

void OSStart (void) After OSInit() and task creating functions

void OSTickInit (void) To initialize System timer ticks

void OSIntEnter (void) Just after the start of ISR codes

void OSIntExit (void) before return form the ISR codes

OS_ENTER_CRITICAL Macro to disable all interrupts

OS_EXIT_CRITICAL Macro to enable all interrupts

9. List the Task service functions in MUCOS.

MUCOS support the following task service functions to create, suspend and resume tasks,

and to set and retrieve time.

unsigned byte

OSTaskCreate (…) Must call before running a task

unsigned byte OSTaskSuspend (..) Called for blocking a task

unsigned byte OSTaskResume (..) Called for resuming a blocked task

void OSTimeset (..) When system time is to be set

unsigned int

OSTimeGet (void) Find present count when time is read

10. List the Time delay functions in MUCOS.

MUCOS Time delay functions are,

void OSTimeDly (…) To delay a task by count-1 value

unsigned byte OSTimeDlyResume (…) To resume a task after a preset delay

void

OSTimeDlyHMSM (…) Time delay to block a task

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11. List the Memory related functions in MUCOS.

MUCOS memory related functions are,

OSMem

*OSMemCreate (…) To create and initialize memory partition

void *OSMemGet (..) To find the pointer of memory control block

unsigned byte

OSMemQuery (..) To find pointers of memory blocks and data structures

unsigned byte

OSMemPut (…) To return a pointer of memory block

12. List the Semaphore related functions in MUCOS.

MUCOS semaphore related functions are,

OS_Event

OSSemCreate (…) To create and initialize a semaphore

void OSSemPend (..) To check whether a semaphore is pending

unsigned short OSSemAccept (..) To check whether SemVal > 0

unsigned byte

OSSemPost (…)

If SemVal = 0 or more, increments, and makes a semaphore

again not pending.

unsigned byte OSSemQuery (…) To get semaphore information

When a semaphore created by OS and used a resource acquiring key, it must be initialized

with “1” to indicate the resource is available.

13. What is a signal in the RTOS environment?

A signal is a flag like intimation to RTOS for development of certain situations during a run

that need urgent attention by executing as ISR.

14. What is meant by task delay?

Time delay is the minimum number of system ticks that a task must wait.

15. What is meant by task resumption?

Task can be scheduled when its turn comes, which was delayed or suspended earlier.

16. What are the different types of scheduling supported by MUCOS?

The different types of scheduling supported by MUCOS are,

(i) Round robin time sliced scheduling.

(ii) Preemptive scheduling.

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17. Explain briefly about the system timer in MUCOS.

There are functions for initiating the system time in MUCOS. Starting a multitasking system

by a first and later suspending if forever is shown as a technique in programming for a

multitasking system.

18. Briefly explain the features supported for mailbox by MUCOS.

MUCOS has mailbox functions and a simple feature that a mailbox has one message pointer

per mailbox. There can be any number of messages or bytes, provided the same pointer

accesses them.

19. Explain briefly the queue functions adapted in MUCOS.

A queue in MUCOS receives from a sender task and array of message pointers. Message

pointers insertion can be such that later on it can retrieve in FIFO method as well as in LIFO

method from a queue. It depends on whether the post was used or post front function was

used, respectively. This helps in taking notice of a high priority message at the queue.

20. List the tasks involved in Automatic Chocolate Vending Machine (ACVM).

Task_ReadPorts Waits for Coins &

Action as per coins collected

Task_Collect Collect coins >= cost, wait till timeout

Task_Deliver Deliver the chocolate

Task_Refund Refund coins, if coins are inserted

in shortage

Task_ExcessRefund Refund coins, if coins are inserted

in excess

Task_Display Display the present operation & status

Task_TimeDateDisplay Updates the display of Time & date

in 3rd line of the LCD display

21. Draw the task synchronization model in ACVM.

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22. What is Cruise control?

Cruise control is a system that takes charge of controlling the throttle from the driver and

cruising the vehicle at a present constant speed. Cruising control may also maintain the

steering stability in case of multiple cars streaming through highways or in case of VIP

convoys.

Cruise control relieves the driver from the duty and driver hands over the charge to ACC

when the road conditions are suitable, and if the car is cruising at high speed when there is

no heavy traffic. The driver resumes the charge in adverse conditions.

23. List the main components of Automatic Cruise Control (ACC).

� Cruise control panel

� Vacuum actuator

� Throttle position sensor

� Throttle valve

� Cruise control system (Embedded System) with inputs from steering wheel, vehicle

speedometer, clutch pedal and brake pedal.

24. List the important hardware standards used in Automotives.

A hardware system in automotive electronics has to provide functional safety. Important

hardware standards and guidance provided at present are the following.

� TTP – Time Triggered Protocol

� CAN – Controller Area Network

� MOST – Media Oriented System Transport

� IEE guidance standard exists for EMC and functional safety.

25. Explain the function of Port_Align and Port_Ranging in ACC.

Port_Align: It is a stepper motor port. Motor steps up clockwise or anticlockwise on an

interrupt signal. The motor helps in aligning the radar in line with the

front-end car.

Port_Ranging: It is a port that determines the range of the front-end car through time

difference. Radar emits a signal and sensor receives the reflected

signal from the front-end car. The time delay between the above two

instances are measured and the range distance of the front-end car is

calculated by multiplying the delay with the speed of the car.

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26. List the special requirements needed in embedded software & RTOS for the automotive

system over and above the features of MUCOS.

� Language can be application specific, and need not be just C / C++.

� OS should be scalable for optimizing memory needs.

� OS should be able to schedule Tasks and ISR in distinct ways.

� Interrupt system should get disabled at the beginning and enabled on return.

� Tasks can be scheduled in real-time.

� Task can consist of three type of objects, event (semaphore), resource (statement and

functions) and devices.

� Timer, task or semaphore objects creation and deletion cannot be allowed.

� IPC, message queue posting by a task is not allowed as a waiting task may wait

indefinitely for its entire message needs.

� Before entering a critical section, interrupt system must be disabled.

27. List the software standards used in automotive electronics.

Software used in automotive electronics must be to industrial standard. The industry

standards are,

� AMI-C (Automotive Mutli-media interface Collaboration) for important software

standards and guidance.

� MISRA-C (Motor Industry Reliability Association Standard) for C language software

guidelines for automotive systems.

� OSEK/VDX for RTOS, Communication and Network management.

28. What is Smart Card?

Smart card is an embedded system-on-chip (SOC) consisting of microcontroller and EEPROM

memory which is used for bank ATM operations, identification, and other innovative

applications.

29. List the contents stored in ROM of smart card.

� Fabrication key

� Personalization key

� RTOS codes

� Application codes

� Utilization lock

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30. List the contents stored in EEPROM / Flash memory of smart card.

� Personal Identification Number (PIN) for user

� Unblocking PIN for use by authorizer (bank)

� Access conditions

� Card user – personal data

� Post issuing data that application generates

� Application’s non-volatile data

� Invalidation lock to lock card after expiry / theft

31. Describe the I/O system of the smart card.

I/O system of the chip and the host interact through asynchronous serial UART at 9.6 / 106 /

115.2 bauds. The communication between the chip and the host may be through gold

contacts or contact less through BPSK modem operating at 13.66 MHz with 10% modulation

index.

32. List special features needed in embedded software for smart card.

� Protected environment (data stored in protected part of ROM)

� Restricted Run-time environment

� OS must be scalable in all aspects

� Code size generated should be optimum

� Limited use of data types

� Three layered file system for data (master, elementary & dedicated)

� Fixed length or variable length file management system with predefined offset.

� It should have classes for networks, sockets, connections, data grams, character I/O

streams, digital certification; DES/AES based cryptography and digital signatures.