MJEmbesys Technocrats

Embedded Interview Questions asked by Interviewer

2019-01-16T14:25:00.001+05:30

EMBEDDED INTERVIEW QUESTION

I have concentrated mostly on embedded software and even I did not consider PCB Layout, Hardware design engineering positions.

I will also update few more questions on analog and digital electronics.

C & C Puzzles

1. C Vs Embedded C vs C++ What is the difference between C and embedded C?

2. C compilation steps

3. Know about “static, global/extern, auto, register, const and volatile” very well. When do you use static keyword for a global variable?

4. Use of volatile keyword?

5. Know about “structure, union and enum”.

6. What is the difference between Structure and union? Where do we use union? Structs and Unions and their paddings.

7. Know about basic pointers concepts. Double Pointers. Pointer aliasing, Multiple indirection.

8. Function pointers and Callback functions

9. Char ptr, int ptr & their sizes? pointer aliasing.

10. Null ptr, void ptr and their uses?

11. malloc vs calloc vs realloc.

12. File operations in linux

13. Typecasting

14. Inline function. Difference between Inline and macro.

15. Preprocessor directives.

16. Bit manipulation - Set, Get, Clear, Toggle, Shift, Display Bits

17. Bit Fields in C

18. Difference between heap and stack? Write a function to figure out if stack grows up or down.

19. Memory leak

C Program to

1. Reverse bits in a number.

2. Count the number of set bits in a byte/word/dword/qword

3. Swap nibbles in a byte

4. Reverse a string.

5. Print the diagonal elements of a matrix.

6. Strip whitespace from a string in-place.

7. Remove duplicate chars from a string ("AAA BBB" -> "A B")

8. Find the first non-repeating character in a string ("ABCA" -> B)

9. Dynamic Memory allocation of a 2D array

10. Transpose of a Matrix

11. Different ways of swapping two numbers.

12. Find size of a data type without sizeof operator.

13. Find little endian or big endian.

14. prints the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz".

Data structures

1. Linked List and its flavors

2. Stack – implementation using arrays and linked list

3. Queue – implementation using arrays and linked list

4. Implement the following functions for a binary tree:
Insert
PrintInOrder
PrintPreOrder
PrintPostOrder
Implement a non-recursive PrintInOrder

Algorithms

1. Know about Time and Space Complexity of basic algorithms

2. Sorting and Searching algorithms.

3. Reverse a linked list, circular linked list

4. To find factorial with and without recursion.

5. To identify the Pythagoras triangle.

6. To identify palindrome.

7. To generate Fibonacci sequence.

8. Find if a linked list has a cycle in it. Now do it without marking nodes (detect loop in linked list)

9. Find the middle of a linked list. Now do it while only going through the list once (same solution as finding cycles)

Computer Architecture – Microprocessor, Microcontrollers (8051), ARM, DSP and other SoC peripherals / Controllers

1. CISC Vs RISC

2. Harvard vs Von Neuman Architecture

3. Flynn’s Taxonomy

4. DMA VS Polling vs Interrupts

5. I/O mapped I/O vs Memory Mapped I/O

6. Virtual Memory

7. Pipeline

8. Instruction Level Parallelism, Thread Level Parallelism.

9. Superscalar Architecture, VLIW Architecture, EPIC Architecture, SMT and Multi-core

10. RAM Vs ROM

11. Various Addressing modes in 8086

12. What are interrupts? Types of interrupts?

13. What is ISR?

14. What is return type of ISR?

15. Can we use any function inside ISR?

16. Can we use printf inside ISR?

17. Can we put breakpoint inside ISR?

18. What is interrupt latency?

19. Types of Cache mapping.

20. what is Snooping Cache?

21. Watchdog Timer

22. Brown out Reset (COP Timer), Power On Reset

23. DRAM/ SDRAM Controller

24. e-Flash Controller

25. Interrupt Controller

26. Timers

27. DMA Controller

Operating System/ Real Time Concepts

1. When do you need an OS?

2. When do you need a RTOS?

3. RTOS VS Time Shared OS?

4. Give some examples of GPOS and RTOS.

5. Soft real-time vs Hard real-time

6. What is Real time and what is RTOS?

7. Difference between various kernels. monolithic kernel, micro kernel, nano kernel, exo kernel, hybrid kernel, resource kernel.

8. What is priority inversion? Why priority inversion occurs and solutions for it?

9. What is priority inheritance?

10. Process vs threads

11. IPC mechanisms

12. Threads- Mutex, semaphore, conditional variables

13. Preemptive vs Non preemptive Scheduling

14. What is scheduling? And its types?

15. What is priority scheduling?

16. What is super loop?

17. Process states

18. Demand paging

19. Kernel

20. Thread

21. What are device-drivers?

22. What are interrupts?

23. What are short-term, medium-term and Long-term Schedulers?

24. What is SMP (Shared Multi-Processing)?

25. What is context switch?

26. What are the information in the PCB?

27. Cpu Bound vs I/O Bound?

28. Memory layout of a process

29. Multithreads

30. Deadlock?

31. Conditions for deadlock?

32. Detecting and avoiding deadlocks?

33. Livelock?

34. Spinlock?

35. Race Condition?

36. Semaphores?

37. Mutex?

38. Binary semaphore vs Count semaphore

39. Semaphore vs Mutex

40. Difference between Mutexes and Critical Sections?
What are Reentrant Locks? Implement a Reentrant Lock with Mutexes.

41. Paging

42. Segmentation

43. Swapping

44. Fragmentation

45. Thrashing

46. What is Top half & bottom half of a kernel?

Linux Concepts

1. Linux commands

2. What are different types of shell and why bash?

3. POSIX API. How pthreads are different from RTOS threads?

Communication / DSP / Networking Concepts

1. Sampling, sampling period & sampling rate

2. cut-off frequency

3. Frequency bandwidth

4. Nyquist theorem

5. Aliasing and Anti-aliasing

6. Signal to Noise Ratio

7. Truncation/ rounding

8. Convolution

9. Correlation

10. FFT

11. FIR, IIR Filters

12. OSI Layers

13. TCP/IP Layers

14. Difference between TCP and UDP? When would you want to use one over the other?

15. Piggybacking

16. ARP

17. DHCP

18. Other basic concepts of Communication

Short range Wireless & On-Chip/Board Communication Protocols

1. I2C

2. SPI

3. CAN

4. LIN

5. UART

6. Bluetooth(Bluetooth Low Energy)

7. Ethernet

8. IEEE 802.11

9. ZigBee

10. PCI

11. LORA

12. Zwave

13. LTE

Analog & Digital Design Concepts – FPGA/ASIC

1. Significance of 32.768KHz frequency as clock source?

2. Different Flip flops, Counters.

3. Sequential Circuit, Combinational Circuit.

4. Binary to Octal, Hexadecimal Conversion.

5. What are Fan in and Fan out?

6. What is Tristate logic?

7. What are error levels?

8. Transition times in gate?

9. MUX, DEMUX, Encoder, Decoder

10. Implement some cicuit with transistor and basic opamp concepts.

11. Frequency divider circuit.

12. Draw 200Hz waveform and then draw 50 Hz wave form wid ref to 200Hz.

13. VLSI Design Flow

14. DAC

15. PWM

16. ADC - Bit resolution during conversion.

17. PLL, Op-Amps, Analog MUX.

18. Designing basic gates using NMOS and PMOS.

19. Draw current gain amplifier using BJT and MOSFET.

General

1. Questions from your project. How did you connect that particular sensor to the board? Any protocol? Clock frequency of the used controller? pinouts of the sensors?

2. Why did you choose that controller for your project and why not the other one?

3. How will you debug a program?

4. What to do if your software in the SoC hangs?

5. Use of JTAG?

6. In-System Programming?

7. How do you use Oscilloscope, Logic Analyzer, Spectrum Analyser, CANanalyzer?

8. Difference between a BIOS and UEFI boot process?

9. Difference between a PC Boot and Smartphone boot?

10. Writing portable code in C.

11. How do you make inline assembly code in C?

12. Explain how shared memory works? (A good candidate will know details like why pointers are stored as offsets and how to protect memory regions using semaphores. )

13. What happens on a system call? (A good answer will include a description of processor interrupts and how the hardware handles them, scheduling decisions, marshaling parameters, etc. (For embedded programmers a question dealing with concurrent operations can be substituted.)

14. How would you read in a string of unknown length without risking buffer overflow?

15. What is ABI/API?

If you want to impress the interviewer, try writing two solutions for C puzzles. 1. Most obvious and simple solution and 2. Obfuscated C code

Before you search for the answers, just hit the upvote. Thanks.

Best of luck !!

2018-12-26T12:44:00.002+05:30

DC MOTOR INTERFACING WITH ARM (LPC2148) CONTROLLER

Motors (Actuators) are important components of embedded systems. Whether it may be a simple DC Motor, or accuracy based Servo Motor, or a precision based Stepper motor, all types of motors are often used in many embedded systems and micro-controller based projects. When talking about simple DC Motors in Micro-controller based system, there are only three tasks we can do: rotate the motor in forward direction, rotate the motor in reverse direction and control the speed of rotation.

In here, we will interface a simple DC Motor with ARM7 based Micro-controller i.e. LPC2148. Here, we will simply change the direction of the rotation of the motor using a Motor Driver IC (L293D). For controlling the speed of rotation of the DC Motor, we will see another project as it involves ADC and PWM concepts.

The aim of this project is to control a simple DC Motor with ARM7 LPC2148 with the help of L293D (Motor driver) IC.

Circuit Diagram

Components Required

All you need to do is connect the motor to the appropriate terminals and provide necessary power supply (separate power supplies for the board and motor driver IC so that we do not over load the power supply).

If you are using a stand – alone board (with crystal and USB – to – UART IC), then you might need the following components.

· ARM7 LPC2148 based Stand – alone board or ARM7 LPC2148 Development Board

· L293D Motor Driver IC

· 12 V DC Motor

· Push button

· Power Supply (separate for Motor Driver IC and MCU board)

· Connecting wires

· USB – to – Mini USB cable

Circuit Design

The design of the circuit is very simple. We need to connect the L293D Motor Driver IC and push buttons to the MCU board.

First is the Motor Driver IC. The L293D Motor Driver IC has a dual H bridge configuration. Hence, it can control two motors simultaneously. But for the demonstration of the project, we will control only a single motor.

L293D is available in a 16 – pin Dual in – line package (DIP) form. Out of the 16 pins, pins 4, 5, 12 and 13 are ground pins. All these pins are connected to ground and optionally a heat sink can also be connected.

Pins 16 and 8 are power supply pins for the internal logic and drivers respectively. They are connected to 5V and 12V supply.

Note: The power supply to the Motor Driver IC must be a different one than the power supply to the MCU board.
Pin 1 is the channel 1 and 2 enable pin. It must be connected to 5V. Pins 2 and 7 are the driver inputs for the motor 1.

They are connected to P1.18 and P1.19 of the LPC2148 MCU respectively. Pins 3 and 6 of the L293D IC are driver outputs and the motor is connected to these pins.

Since we need to control the direction of the motor, we are going to use a push button to decide the direction. A push button is connected to P0.16 of the MCU.

Rest of the connections like Crystal, USB – to – UART, etc. will be already made on the development board or stand – alone board. With this, the design of the circuit is complete.

Note: The development board used in this project already has all the required components like motor diver, push buttons etc. on it. Hence, there is no need for any extra connections. All we need to do is to connect the motor to the driver output pins of the motor driver IC.

Working of the Project

The aim of this project is to demonstrate the DC Motor control using ARM7 LPC2148 MCU. Since motors draw a significant amount of current, we need a separate IC called Motor Driver IC like L293D for example. The working of the project is explained here.

This is a simple project which helps us in controlling the direction of rotation of the motor using LPC2148. When the system is powered on, the status of the button is read by the MCU. As per the program, when the button is not pressed, the motor rotates in forward direction.

Whenever the button is pressed, a change in state at the button pin is detected by the MCU and the motor rotates in reverse directions. The project is better understood by analyzing the program which is explained in the next section.

Program

#include<lpc21xx.h>

void delay(int count);

void main()

{

IODIR1=0x00000033; //Set direction of IN1, IN2,IN3,IN4

while(1)

{

IOSET1=0x00000011; //set IN1, IN3=1

IOCLR1=0x00000022; //Clear IN2, IN4=0

delay(1000);

IOSET1=0x00000022; //set IN1, IN3=1

IOCLR1=0x00000011; //Clear IN2, IN4=0

delay(250);

IOSET1=0x00000011; //set IN1, IN3=0

IOCLR1=0x00000022; //Clear IN2 IN4=1

delay(1000);

}

void delay(int count)

{

int j=0,i=0;

for(j=0;j<count;j++)

{

/* At 60Mhz, the below loop introduces

delay of 10 us */

for(i=0;i<1275;i++);

}

Understanding the Program

The basic components of the program include PLL for setting up system and peripheral clock and GPIO pins for interfacing with motor and button. First, we will see how to initialize the pins to operate in GPIO mode.
By default, all the pins are configured to work as GPIO pins. Hence, we need not do anything specifically. In case we want to explicitly configure the pins as GPIO, then the following commands must be used. The GPIO Tutorial will give more information about the pins.

PINSEL0 = 0x00000000; // Making all the pins as GPIO

PINSEL1 = 0x00000000;

PINSEL2 = 0x00000000;

The next module we need to configure is the PLL. PLL Module in LPC2148 MCU is used to set the system clock and peripheral clock as per the user or programmer wishes.

The maximum clock frequency for LPC2148 is 60 MHz. By using the following set of instructions, we can set the system clock i.e. CCLK and peripheral clock i.e. PCLK at 60 MHz respectively. More information about the PLL module is explained in the ARM PLL tutorial.

PLL0CON = 0x01; // PLL0 module is enabled

PLL0CFG = 0x24; // Multiplier and Divider values of the PLL are set

PLL0FEED = 0xAA; // Feed sequence for locking the PLL0 at 60 MHz

PLL0FEED = 0x55;

while (! (PLL0STAT & 0x00000400)); // Waiting for Lock status of the PLL

PLL0CON = 0x03; // PLL0 is enabled again and connected

PLL0FEED = 0xAA; // Feed sequence for setting the PLL0 as CCLK

PLL0FEED = 0x55;

VPBDIV = 0x01; // PCLK is set same as CCLK

Once the CCLK and PCLK are running at 60 MHz, the final part of the program is to read the status of the Button. After reading the status of the button, we can rotate the motor in either forward direction or reverse direction.

8051 INTERRUPT

2018-12-22T16:57:00.001+05:30

Interrupts:

The interrupts refer to a notification, communicated to the controller, by a hardware device or software, on receipt of which controller momentarily stops and responds to the interrupt. Whenever an interrupt occurs the controller completes the execution of the current instruction and starts the execution of an Interrupt Service Routine (ISR) or Interrupt Handler. ISR is a piece of code that tells the processor or controller what to do when the interrupt occurs. After the execution of ISR, controller returns back to the instruction it has jumped from (before the interrupt was received). The interrupts can be either hardware interrupts or software interrupts.

Interrupt Sources:

Original 8051 has 6 sources of interrupts

· Reset

· Timer 0 overflow

· Timer 1 overflow

· External Interrupt 0

· External Interrupt 1

· Serial Port events buffer full, buffer empty, etc)

External interrupt Example: (INT0):

include<reg51.h>

sbit rs=P3^0;

sbit rw=P3^1;

sbit en=P3^3;

void command();

void display();

unsigned int arr1[5]={0x38,0x06,0x01,0x0e,0x80};

unsigned char arr2[10]=

{0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x27,0x7f,0x6f};

unsigned char arr3[14]={"WELCOME TO ALL"};

int a,b,c;

int i,j;

void de(unsigned int n);

void ISR()interrupt 0

{

for(a=0;a<=9;a++)

{

P2=arr2[a];

de(100);

}

void main()

{

IE=0x81;

while(1)

{

for(b=0;b<=4;b++)

{

P1=arr1[b];

command();

}

for(c=0;c<=13;c++)

{

P1=arr3[c];

display();

}

void de(unsigned int n)

{

for(i=0;i<=n;i++)

{

for(j=0;j<=1000;j++);

}

void command()

{

rs=0;

rw=0;

en=1;

de(100);

en=0;

}

void display()

{

rs=1;

rw=0;

en=1;

de(100);

en=0;

}

Importance of Crystal In Embedded

2018-12-16T18:30:00.003+05:30

What is Crystal Oscillator Circuit and its Working?

An electronic circuit or electronic device that is used to generate periodically oscillating electronic signal is called as an electronic oscillator. The electronic signal produced by an oscillator is typically a sine wave or square wave. An electronic oscillator converts the direct current signal into an alternating current signal. The radio and television transmitters are broad casted using the signals generated by oscillators. The electronic beep sounds and video game sounds are generated by the oscillator signals. These oscillators generate signals using the principle of oscillation.

There are different types of oscillator electronic circuits such as Linear oscillators – Hartley oscillator, Phase-shift oscillator, Armstrong oscillator, Clapp oscillator, Colpitts oscillator, and so on, Relaxation oscillators – Royer oscillator, Ring oscillator, Multivibrator, and so on, and Voltage Controlled Oscillator (VCO). In this article, let us discuss in detail about Crystal oscillator like what is crystal oscillator, crystal oscillator circuit, working, and use of crystal oscillator in electronic circuits.

What is Crystal Oscillator?

An electronic circuit that is used to generate an electrical signal of precise frequency by utilizing the vibrating crystal’s mechanical resonance made of piezoelectric material. There are different types of piezoelectric resonators, but typically, quartz crystal is used in these types of oscillators. Hence, these oscillator electronic circuits are named as crystal oscillators.

The above figure shows the equivalent circuit diagram of quartz crystal in an electronic oscillator that consists of resistor, inductor, and capacitors which are connected as shown in the figure.

Crystal Oscillator Working

The atoms, molecules, ions are packed in an order in three spatial dimensions with repeating pattern to form a solid that can be called as a crystal. The crystal can be made by almost any object that is made of elastic material by using appropriate electrical transducers. As every object consists of natural resonant frequency of vibration, steel consists of high speed of sound and is also very elastic.

Thus, steel is frequently used instead of quartz in mechanical filters. This resonant frequency depends on different parameters such as size, elasticity, speed of sound, and shape of the crystal. In general, the shape of high frequency crystals is simple rectangular plate and the shape of low frequency crystals is tuning fork shape as shown in the figure below.

Crystal oscillator circuit works on the principle of the inverse piezoelectric effect, i.e., a mechanical deformation is produced by applying an electric field across certain materials. Thus, it utilizes the vibrating crystal’s mechanical resonance which is made of a piezoelectric material for generating an electrical signal of a specific frequency.

These quartz crystal oscillators are highly stable, consists of good quality factor, they are small in size, and are very economical. Hence, quartz crystal oscillator circuits are superior compared to other resonators such as LC circuits, turning forks, and so on. Generally, 8MHz crystal oscillator is used in microprocessors and microcontrollers.

The equivalent electrical circuit also represents the crystal action of the crystal. The basic components used in the circuit, inductance L1 represent crystal mass, capacitance C1 represents compliance, resistance R1 represents the crystal’s internal structure friction, and C0 is used to represent the capacitance that is formed because of crystal’s mechanical moulding.

The quartz crystal oscillator circuit diagram consists of series resonance and parallel resonance, i.e., two resonant frequencies. If the reactance produced by capacitance C1 is equal and opposite to the reactance produced by inductance L1, then the series resonance occurs. The series and parallel resonant frequencies are represented by fs and fp respectively, and the values of fs and fp can be determined by using the following equations shown in the figure below.

Use of Crystal Oscillator

In general, we know that, crystal oscillators are used in the microprocessors and microcontrollers for providing the clock signals. Let us consider 8051 microcontroller for which an external crystal oscillator circuit of 12MHz is essential, even though (based on model) 8051 microcontroller is capable to run at 40 MHz (max). 8051 requires 12 clock cycles for one machine cycle, such that to give effective cycle rate at 1MHz (considering 12MHz clock) to 3.33MHz (considering maximum 40MHz clock). This crystal oscillator is used to generate clock pulses required for the synchronization of all the internal operations.

There are numerous applications for crystal oscillator in various fields and a few crystal oscillator applications are shown below:

Application of Crystal Oscillator in Military and Aerospace

The use of crystal oscillator in military and aerospace, is to establish an efficient communication system, for the navigation purpose, electronic warfare, in the guidance systems, and so on.

Use of Crystal Oscillator in Research and Measurement

The crystal oscillator is used in research and measurement for celestrial navigation, space tracking purpose, in the measuring instruments and medical devices, and so on.

Industrial Applications of Crystal Oscillator

There are a huge number of industrial applications of crystal oscillator such as in computers, digital systems, instrumentation, phase locked loop systems, marine, modems, sensors, telecommunications, disk drives, and so on.

Use of Crystal Oscillator in Automotive

Crystal oscillator is used for engine controlling, stereo, clock and to trip computer, and in GPS system.

Consumer Applications of Crystal Oscillator

Crystal oscillators are used in many consumer goods such as cable television systems, personal computers, video cameras, toys and video games, radio systems, cellular phones, and so on.

Do you know the types of crystal oscillator circuits? Furthermore, technical assistance can be provided based on your comments posted in the comments below.

RTC Interfacing with 8051

2018-12-16T18:13:00.002+05:30

RTC-DS1307 Interfacing with 8051

The Real-time clock DS1307 IC basically is stand-alone time clock with following features.

· Real-time clock (RTC) counts seconds, minutes, hours, date of the month, month, the day of the week, and year with leap-year compensation valid up to 2100.

· The clock operates in either the 24-hour or 12-hour format with AM/PM indicator.

· 56-byte, battery-backed, non-volatile (NV) RAM for data storage

· Two-wire(I2C) serial interface

· Programmable squarewave output signal

· Automatic power-fail detect and switch circuitry

· Consumes less than 500nA in battery backup mode with oscillator running

· Optional industrial temperature range: -40°C to +85°C

DS1307 Pins

Below image shows the pin diagram and the recommended connections for DS1307.

VCC, GND: These pins are used to provide the power to the chip. When 5V is applied within normal limits, the device is fully accessible and data can be written and read. When a 3V battery is connected to the device and VCC is below 1.25 x VBAT, reads and writes are inhibited. However, the timekeeping function continues unaffected by the lower input voltage. As VCC falls below VBAT the RAM and timekeeper are switched over to the external power supply (nominal 3.0V DC) at VBAT.

X1-X2:Pins to connect the external 32.768kHz oscillator that provides the clock source to the chip.

Vbat: A 3.3v Lithium battery can be connected to this pin in order to provide the power source when the external supply voltage is not available. Battery voltage must be held between 2.0V and 3.5V for proper operation.

SCL: This pin must be connected to SCL pin of the I2C Bus/Master.

SDA: This pin must be connected to SDA pin of the I2C Bus/Master.

SQW/OUT: When enabled, the SQWE bit set to 1, the SQW/OUT pin outputs one of four square wave frequencies (1Hz, 4kHz, 8kHz, 32kHz).

· Note: The SCL,SDA, and SQW are open drain and must be pulled up with appropriate pull-up resistors as shown in the image.

DS1307 Memory

The RTC keeps the date and time arranged in it's memory as shown below:

Control Register
7	6	5	4	3	2	1	0
OUT	0	0	SQWE	0	0	RS1	RS0

OUT: This bit controls the output level of the SQW/OUT pin when the square-wave output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1 and is 0 if OUT = 0. By default this pin will be 0.

SQWE:This bit, when set to logic 1, enables the oscillator output. The frequency of the square-wave output depends on the value of the RS0 and RS1 bits.

RS1-RS0:These bits control the frequency of the square-wave output when the squarewave output has been enabled.

DS1307 ID

Ds1307 ID
7	6	5	4	3	2	1	0
1	1	0	1	0	0	0	R/W

· R/W is 0 then data is Written to RTC

· R/W is 1 then data is Read from RTC

Steps to initialize DS1307

1. Start the I2C communication.

2. Send the DS1307 address and select write operation

3. Send the Address of Control Register for sending the command.

4. Send the Command to Disable the SQW Out.

5. Stop the Communication.

Steps to Write Date and Time

1. Start the I2C communication.

2. Send the DS1307 address and select write operation

3. Send the Address of SECOND Register for writing the second value.

4. Write the Sec,min,hour,weekDay,date,month,year one by one.

5. Stop the Communication.

Steps to Read Date and Time

1. Start the I2C communication.

2. Send the DS1307 address and select write operation

3. Send the Address of SECOND Register for reading the second value.

4. Stop the Communication.

5. Send the DS1307 address and select Read operation

6. Read the Sec,min,hour,weekDay,date and month one by one and send positive acknowledgement.

7. Read the Year and send the Neg/No Acknowledgement.

8. Stop the Communication.

Note: The date and time read from Ds1307 will be of BCD format, like:

· 0x12,0x39,0x26 for 12hr,39min and 26sec.

· 0x15,0x08,0x47 for 15th day,8th month and 47th year

#include "rtc.h"
	#include "lcd.h"
	int main()
	{
	rtc_t rtc;

	/Connect RS->P2.0, RW->P2.1, EN->P2.2 and data bus to P2.4 to P2.7/
	LCD_SetUp(P2_0,P2_1,P2_2,P_NC,P_NC,P_NC,P_NC,P2_4,P2_5,P2_6,P2_7);
	LCD_Init(2,16);

	/Connect SCL->P0.6, SDA->P0.7/
	RTC_Init();
	rtc.hour = 0x10; // 10:40:20 am
	rtc.min = 0x40;
	rtc.sec = 0x00;

	rtc.date = 0x01; //1st Jan 2016
	rtc.month = 0x01;
	rtc.year = 0x16;
	rtc.weekDay = 5; // Friday: 5th day of week considering monday as first day.
	/*##### Set the time and Date only once. Once the Time and Date is set, comment these lines
	and reflash the code. Else the time will be set every time the controller is reset*/
	RTC_SetDateTime(&rtc); // 10:40:20 am, 1st Jan 2016
	/* Display the Time and Date continuously */
	while(1)
	{
	RTC_GetDateTime(&rtc);
	LCD_GoToLine(0);
	LCD_Printf("time:%2x:%2x:%2x \nDate:%2x/%2x/%2x",(uint16_t)rtc.hour,(uint16_t)rtc.min,(uint16_t)rtc.sec,(uint16_t)rtc.date,(uint16_t)rtc.month,(uint16_t)rtc.year);
	}
	return (0);
	}

Embedded MCQ Questions

2018-12-16T16:52:00.002+05:30

1. A micro controller at-least should consist of:
a) RAM, ROM, I/O devices, serial and parallel ports and timers
b) CPU, RAM, I/O devices, serial and parallel ports and timers
c) CPU,RAM, ROM, I/O devices, serial and parallel ports and timers
d) CPU, ROM, I/O devices and timers

2. Unlike micro processors, micro controllers make use of batteries because they have:
a) high power dissipation
b) low power consumption
c) low voltage consumption
d) low current consumption

3. What is the order decided by a processor or the CPU of a controller to execute an instruction?
a) decode,fetch,execute
b) execute,fetch,decode
c) fetch,execute,decode
d) fetch,decode,execute

4. How are micro controllers classified on the basic of internal bus width?
a) 8,16,32,64 bits
b) 4,8,16,32 bits
c) 8,16 bits
d) 4,16,32 bits

5. How is the performance and the computer capability affected by increasing its internal bus width?
a) it increases and turns better
b) it decreases
c) remains the same
d) internal bus width don’t affect the performance in any way

6. Abbreviate CISC and RISC.
a) Complete Instruction Set Computer, Reduced Instruction Set Computer
b) Complex Instruction Set Computer, Reduced Instruction Set Computer
c) Complex Instruction Set Computer, Reliable Instruction Set Computer
d) Complete Instruction Set Computer, Reliable Instruction Set Computer

7. Give the names of the buses present in a controller for transferring data from one place to another?
a) data bus, address bus
b) data bus
c) data bus, address bus, control bus
d) address bus

8. What is the file extension that is loaded in a micro controller for executing any instruction?
a) .doc
b) .c
c) .txt
d) .hex

9. What are the most appropriate criterion for choosing the right micro controller of our choice?
a) speed
b) availability
c) ease with the product
d) all of the mentioned

10. Why micro controllers are not called general purpose devices?
a) because they are based on VLSI technology
b) because they are not meant to do a single work at a time
c) because they are cheap
d) because they consume low power

11. How many types of architectures are available, for designing a device that is able to work on its own?
a) 3
b) 2
c) 1
d) 4

12. Which architecture is followed by general purpose microprocessors?
a) Harvard architecture
b) Von Neumann architecture
c) none of the mentioned
d) all of the mentioned

13. Which architecture involves both the volatile and the non volatile memory?
a) Harvard architecture
b) Von Neumann architecture
c) none of the mentioned
d) all of the mentioned

14. Which architecture provides separate buses for program and data memory?
a) Harvard architecture
b) Von Neumann architecture
c) none of the mentioned
d) all of the mentioned

15. Which micro controller don’t match with its architecture below?
a) Microchip PIC- Harvard
b) MSP430- Harvard
c) ARM7- Von Neumann
d) ARM9- Harvard

16. Harvard architecture allows:
a) separate program and data memory
b) pipe-ling
c) complex architecture
d) all of the mentioned

17. Which out of the following supports Harvard architecture?
a) ARM7
b) Pentium
c) SHARC
d) all of the mentioned

18. Why most of the DSPs use Harvard architecture?
a) they provide greater bandwidth
b) they provide more predictable bandwidth
c) none of the mentioned
d) both of the mentioned

19. Which of the following supports CISC as well as Harvard architecture?
a) ARM7
b) ARM9
c) SHARC
d) none of the mentioned

20. n Neumann
c) none of the mentioned
d) both of the mentioned

21. . 8051 series of micro controllers are made by which of the following companies?
a) Atmel
b) Philips
c) none of the mentioned
d) both of the mentioned

22. AT89C2051 has RAM of:
a) 128 bytes
b) 256 bytes
c) 64 bytes
d) 512 bytes

23. 8051 series has how many 16 bit registers?
a) 2
b) 3
c) 1
d) 0

24. When 8051 wakes up then 0x00 is loaded to which register?
a) DPTR
b) SP
c) PC
d) PSW

25. When the micro controller executes some arithmetic operations, then the flag bits of which register are affected?
a) PSW
b) SP
c) DPTR
d) PC

26. How is the status of the carry, auxiliary carry and parity flag affected if write instruction
MOV A,#9C
ADD A,#64H
a) CY=0,AC=0,P=0
b) CY=1,AC=1,P=0
c) CY=0,AC=1,P=0
d) CY=1,AC=1,P=1

27. How are the bits of the register PSW affected if we select Bank2 of 8051?
a) PSW.5=0 and PSW.4=1
b) PSW.2=0 and PSW.3=1
c) PSW.3=1 and PSW.4=1
d) PSW.3=0 and PSW.4=1

28. If we push data onto the stack then the stack pointer
a) increases with every push
b) decreases with every push
c) none of the mentioned
d) both of the mentioned

29. On power up, the 8051 uses which RAM locations for register R0- R7
a) 00-2F
b) 00-07
c) 00-7F
d) 00-0F

30. How many bytes of bit addressable memory is present in 8051 based micro controllers?
a) 8 bytes
b) 32 bytes
c) 16 bytes
d) 128 bytes

31. DJNZ R0,label is how many bit instruction?
a) 2
b) 3
c) 1
d) Cant be determined

32. JZ, JNZ, DJNZ, JC, JNC instructions monitor the bits of which register ?
a) DPTR
b) B
c) A
d) PSW

33. Calculate the jump code for again and here if code starts at 0000H

34. MOV R1,#0

35. MOV A,#0

36. MOV R0,#25H

37. AGAIN:ADD A,#0ECH

38. JNC HERE

39. HERE: INC R1

40. DJNZ R0,AGAIN

41. MOV R0,A

42. END

43. a)F3,02
b)F9,01
c)E9,01
d)E3,02

44. When the call instruction is executed the top most element of stack comes out to be
a) the address where stack pointer starts
b) the address next to the call instruction
c) address of the call instruction
d) next address of the stack pointer

45. LCALL instruction takes
a) 2 bytes
b) 4 bytes
c) 3 bytes
d) 1 byte

46. Are PUSH and POP instructions are a type of CALL instructions?
a) yes
b) no
c) none of the mentioned
d) cant be determined

47. What is the time taken by one machine cycle if crystal frequency is 20MHz?
a) 1.085 micro seconds
b) 0.60 micro seconds
c) 0.75 micro seconds
d) 1 micro seconds

48. Find the number of times the following loop will be executed

MOV R6,#200

BACK:MOV R5,#100

HERE:DJNZ R5, HERE

DJNZ R6,BACK

END

a)100
b)200
c)20000
d)200000

8051 interview Questions for Beginners

2018-12-16T16:50:00.004+05:30