IT2354-EMBEDDED SYSTEMS Two Marks Questions With Answers 2014

Anna University, Chennai


2 marks:




1. Define Embedded System. What are the components of embedded system?

An Embedded system is one that has computer hardware with software embedded in it as one of its most important component.

The three main components of an embedded system are

1. Hardware

2. Main application software


2. In what ways CISC and RISC processors differ?



It provides number of addressing


It provides very few

addressing modes

It has a micro programmed unit with a

control memory

It has a hardwired unit

without a control memory

An easy compiler design

Complex compiler design

Provide precise and intensive

calculations slower than a RISC

Provide precise and

intensive calculations faster than a CISC

3. Define system on chip (SOC) with an example

Embedded systems are being designed on a single silicon chip called system on chip. SOC is a new design innovation for embedded system

Ex. Mobile phone.

4. Give any two uses of VLSI designed circuits

A VLSI chip can embed IPs for the specific application besides the ASIP or a GPP core. A

system on a VLSI chip that has all of needed analog as well as digital circuits.

Eg. Mobile phone.

5. List the important considerations when selecting a processor.

§ Instruction set

§ Maximum bits in an operand

§ Clock frequency

§ Processor ability

6. What are the types of embedded system?

§ Small scale embedded systems

§ Medium scale embedded systems

§ Sophisticated embedded systems

7. Classify the processors in embedded system?

1. General purpose processor Microprocessor Microcontroller Embedded processor Digital signal processor Media processor

2. Application specific system processor

3. Multiprocessor system using GPP and ASSP GPP core or ASIP core integrated into either an ASIC or a VLSI circuit or an FPGA core integrated with processor unit in a VLSI chip.

8. What are the important embedded processor chips?

v ARM 7 and ARM 9

v i 960

v AMD 29050

9. Name some DSP used in embedded systems?

v TMS320Cxx


v 5600xx

10. Name some of the hardware parts of embedded systems?

Ø Power source

Ø Clock oscillator circuit

Ø Timers

Ø Memory units


Ø LCD and LED displays

Ø Keyboard/Keypad

11. What are the various types of memory in embedded systems?

· RAM (internal External)


· Cache memory

12. What are the points to be considered while connecting power supply rails with embedded


Ø A processor may have more than two pins of Vdd and Vss

Ø Supply should separately power the external I/O driving ports, timers, and clock


Ø From the supply there should be separate interconnections for pairs of Vdd and

Vss pins analog ground analog reference and analog input voltage lines.

13. What is watch dog timer?

Watch dog timer is a timing device that resets after a predefined timeout.

14. What are the two essential units of a processor on a embedded system?

Program Flow control Unit

Execution Unit

15. What does the execution unit of a processor in an embedded system do?

The EU includes the ALU and also the circuits that execute instructions for a program control task. The EU has circuits that implement the instructions pertaining to data transfer operations and data conversion from one form to another.

16. Give examples for general purpose processor.

· Microcontroller

· Microprocessor

17. Define microprocessor.

A microprocessor is a single VLSI chip that has a CPU and may also have some other units for example floating point processing arithmetic unit pipelining and super scaling units for faster processing of instruction.


1. Differentiate synchronous communication and iso-synchronous communication.

Synchronous communication

When a byte or a frame of the data is received or transmitted at constant time intervals with uniform phase difference, the communication is called synchronous communication.

Iso-synchronous communication

Iso-synchronous communication is a special case when the maximum time interval can be varied.

2. What are the two characteristics of synchronous communication?

Bytes maintain a constant phase difference

The clock is not always implicit to the synchronous data receiver.

3. What are the three ways of communication for a device?

· Iso-synchronous communication

· synchronous communication

· Asynchronous communication

4. Expand a) SPI b) SCI

SPI—serial Peripheral Interface

SCI—Serial Communication Interface

5. Define software timer.

This is software that executes and increases or decreases a count variable on an interrupt from a timer output or form a real time clock interrupt. A software timer can also generate interrupt on overflow of count value or on finishing value of the count variable.

6. What is I2C?

I2C is a serial bus for interconnecting ICs .It has a start bit and a stop bit like an UART. It has seven fields for start,7 bit address, defining a read or a write, defining byte as acknowledging byte, data byte, NACK and end.

7. What are the bits in I2C corresponding to?

It has seven fields for start,7 bit address, defining a read or a write, defining byte as acknowledging byte, data byte, NACK and end

8. What is a CAN bus? Where is it used?

CAN is a serial bus for interconnecting a central Control network. It is mostly used in automobiles. It has fields for bus arbitration bits, control bits for address and data length data bits, CRC check bits, acknowledgement bits and ending bits.

9. What is USB? Where is it used?

USB is a serial bus for interconnecting a system. It attaches and detaches a device from the network. It uses a root hub. Nodes containing the devices can be organized like a tree structure. It is mostly used in networking the IO devices like scanner in a computer system.

10. What are the features of the USB protocol?

A device can be attached, configured and used, reset, reconfigured and used, share the bandwidth with other devices, detached and reattached.

11. Explain briefly about PCI and PCI/X buses.

PCI and PCI/X buses are independent from the IBM architecture .PCI/X is an extension of PCI and support 64/100 MHZ transfers. Lately, new versions have been introduced for the PCI bus architecture.

12. Why are SPCI parallel buses important?

SPCI serial buses are important for distributed devices. The latest high speed sophisticated systems use new sophisticated buses.

13. What is meant by UART?

UART stands for universal Asynchronous Receiver/Transmitter.

· UART is a hardware component for translating the data between parallel and

serial interfaces.

· UART does convert bytes of data to and from asynchronous start stop bit.

· UART is normally used in MODEM.

14. What does UART contain?

· A clock generator.

· Input and Output start Registers

· Buffers.

· Transmitter/Receiver control.

15. What is meant by HDLC?

· HDLC stands for “High Level Data Link Control”.

· HDLC is a bit oriented protocol.

· HDLC is a synchronous data Link layer.

16. Name the HDLC’s frame structure?







17.List out the states of timer?

There are eleven states as follows

· Reset state

· Idle state

· Present state

· Over flow state

· Over run state

· Running state

· Reset enabled state / disabled

· Finished state

· Load enabled / disabled

· Auto reload enabled / disabled

· Service routine execution enabled / disabled

18. Name some control bit of timer?

· Timer Enable

· Timer start

· Up count Enable

· Timer Interrupt Enable

19. What is meant by status flag?

Status flag is the hardware signal to be set when the timer reaches zeros.

20.List out some applications of timer devices?

· Real Time clock

· Watchdog timer

· Input pulse counting


· Scheduling of various tasks

21.State the special features on I2C?

· Low cost

· Easy implementation

· Moderate speed (upto 100 kbps).

22.What are disadvantages of I2C?

· Slave hardware does not provide much support

· Open collector drivers at the master leads to be confused

23.What are the two standards of USB?

· USB 1.1

· USB 2.0

24.Draw the data frame format of CAN?






Data field

CRC field



End of frame

1 12 6 0-64 16 2 7

25. What is the need of Advanced Serial High Speed Buses?

If the speed in the rate of „Gigabits per second‟ then there is a need of Advanced Serial

High Speed Buses.

26.What is meant by ISA?

· ISA stands for Industry standard Architecture.

· Used for connecting devices following IO addresses and interrupts vectors as

per IBM pc architecture.

27.What is meant by PCI-X?

· PCI X offers more speed over PCI.

· 30 times more speed than PCI.

28.Define CPCI?

· CPCI stands for Compact peripheral component Interfaces.

· CPCI is to be connected via a PCI.

· CPCI is used in the areas of Telecommunication Instrumentation abd data

communication applications.

29.Define half-duplex communication.

Transmission occurs in both the direction, but not simultaneously.

30. Define full duplex communication.

Transmission occurs in both the direction, simultaneously

31. Define Real Time Clock (RTC)?

Real time clock is a clock which once the system stats does not stop and cant be reset and its count value cant be reloaded.

32. Define Time-out or Time Overflow?

A state in which the number of count inputs exceeded the last acquirable value and on reaching that state, an interrupt can be generated.

33. Why do we need at least one timer in an ES?

The embedded system needs at least on timer device. It is used as a system clock.


1. What are the states of a process?

a. Running b. Ready

c. Waiting

2. What is the function in steady state?

Processes which are ready to run but are not currently using the processor are in the 'ready'


3. Define scheduling.

This is defined as a process of selection which says that a process has the right to use the processor at given time.

4. What is scheduling policy?

It says the way in which processes are chosen to get promotion from ready state to running state.

5. Define hyper period?

It refers the duration of time considered and also it is the least common multiple of all the processe

6. What is schedulability?

It indicates any execution schedule is there for a collection of process in the system's functionality.

7. What are the types of scheduling?

1. Time division multiple access scheduling.

2. Round robin scheduling.

8. What is cyclostatic scheduling?

In this type of scheduling, interval is the length of hyper period 'H'. For this interval, a cyclostatic schedule is separated into equal sized time slots.

9. Define round robin scheduling?

This type of scheduling also employs the hyperperiod as an interval. The processes are

run in the given order.

10. What is scheduling overhead?

It is defined as time of execution needed to select the next execution process.

11. What is meant by context switching?

The actual process of changing from one task to another is called a context switch.

12. Define priority scheduling?

A simple scheduler maintains a priority queue of processes that are in the runnable state.

13. What is rate monotonic scheduling?

Rate monotonic scheduling is an approach that is used to assign task priority for a preemptive system.

14. What is critical instant?

It is the situation in which the process or task posses‟ highest response time.

15. What is critical instant analysis?

It is used to know about the schedule of a system. Its says that based on the periods given, the priorities to the processes has to be assigned.

16. Define earliest deadline first scheduling?

This type of scheduling is another task priority policy that uses the nearest deadline as the criterion for assigning the task priority.

17. What is IDC mechanism?

It is necessary for a 'process to get communicate with other process' in order to attain a specific application in an operating system.

18. What are the two types of communication?

1. Blocking communication 2. Non blocking communication


1. Name the important terms of RTOS?

Task State Scheduler

Shared data


2. Define process.

Process is a computational unit that processes on a CPU under the control of a scheduling

kernel of an OS. It has a process structure, called Process control block. A process defines a sequentially executing program and its state.

3. What is meant by PCB?

Process Control Block‟ is abbreviated as PCB.PCB is a data structure which contains all

the information and components regarding with the process.

4. Draw the process state transitions?

A w a k e D i s p a t c h R u n n i n g B l o c k

clip_image003T i m e t u r n o u t

R e a d y B l o c k e d

A s l e e p

W a k e u p

5. Define task and Task state.

A task is a set of computations or actions that processes on a CPU under the control of a scheduling kernel. It also has a process control structure called a task control block that saves at the memory. It has a unique ID. It has states in the system as follows: idle, ready, running, blocked and finished

6. Define Task Control Block (TCB)

A memory block that holds information of program counter, memory map, the signal dispatch table, signal mask, task ID, CPU state and a kernel stack.

7. What is a thread?

Thread is a concept in Java and UNIX and it is a light weight sub process or process in an application program. It is controlled by the OS kernel. It has a process structure, called thread stack, at the memory. It has a unique ID .It have states in the system as follows: stating, running, blocked and finished.

8. Define Inter process communication.

An output from one task passed to another task through the scheduler and use of signals, exception, semaphore, queues, mailbox, pipes, sockets, and RPC.

9. What is shared data problem?

If a variable is used in two different processes and another task if interrupts before the operation on that data is completed then the value of the variable may differ from the one expected if the earlier operation had been completed .This ids known as shared data problem.

10. Define Semaphore.

Semaphore provides a mechanism to let a task wait till another finishes. It is a way of synchronizing concurrent processing operations. When a semaphore is taken by a task then that task has access to the necessary resources. When given the resources unlock. Semaphore can be used as an event flag or as a resource key.

11. Define Mutex.

A phenomenon for solving the shared data problem is known as semaphore. Mutex is a semaphore that gives at an instance two tasks mutually exclusive access to resources.

12. Differentiate counting semaphore and binary semaphore. Binary semaphore

When the value of binary semaphore is one it is assumed that no task has taken it and that it has been released. When the value is 0 it is assumed that it has been taken.

Counting semaphore

Counting semaphore is a semaphore which can be taken and given number of times. Counting semaphores are unsigned integers.

13. What is Priority inversion?

A problem in which a low priority task inadvertently does not release the process for a higher priority task.

14. What is Deadlock situation?

A set of processes or threads is deadlocked when each process or thread is waiting for a resource to be freed which is controlled by another process.

15. Define Message Queue.

A task sending the multiple FIFO or priority messages into a queue for use by another task using queue messages as an input.

16. Define Mailbox and Pipe.

A message or message pointer from a task that is addressed to another task.

17. Define Socket.

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

18. Define Remote Procedure Call.

A method used for connecting two remotely placed methods by using a protocol. Both systems work in the peer to peer communication mode and not in the client server mode.

19. What are the goals of RTOS?

Ø Facilitating easy sharing of resources

Ø Facilitating easy implantation of the application software

Ø Maximizing system performance

Ø Providing management functions for the processes, memory, and I/Os and for other

functions for which it is designed.

Ø Providing management and organization functions for the devices and files and file like


Ø Portability

Ø Interoperability

Ø Providing common set of interfaces.

20. What is RTOS?

An RTOS is an OS for response time controlled and event controlled processes. RTOS is an OS for embedded systems, as these have real time programming issues to solve.

21. List the functions of a kernel.

Ø Process management

Ø Process creation to deletion

Ø Processing resource requests

Ø Scheduling


Ø Memory management

Ø I/O management

Ø Device management

22. What are the two methods by which a running requests resources?

· Message

· System call

23.What are the functions of device manager?

Ø Device detection and addition

Ø Device deletion

Ø Device allocation and registration

Ø Detaching and deregistration

Ø Device sharing

24. List the set of OS command functions for a device

Ø Create and open

Ø Write

Ø Read

Ø Close and delete

1. What is a PIC?


PIC refers to Programmable Intelligent Computer. PIC is microprocessor lies inside a personal computer but significantly simpler, smaller and cheaper. It can be used for operating relays, measuring sensors etc.

2. What are the main elements inside a PIC?

Processing engine, Program memory, data memory and Input/Output.

3. What are the types of program memory in a PIC?

Read-only, EPROM and EEPROM, Flash

4. What is MBasic Compiler Software?

From version onward, Basic Micro offers one version of its MBasic compiler, the “Professional” version. MBasic runs under Microsoft‟s Windows operating system in any version from Windows 95 to Windows XP. The computer requires an RS-232 port for connection to

the ISP-PRO programmer board.

5. Define pseudo-code.

Pseudo-code is a useful tool when developing an idea before writing a line of true code or when explaining how a particular procedure or function or even an entire program