DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

EC6504 MICROPROCESSOR AND MICRO CONTROLLER

UNIT - I : THE 8086 MICROPROCESSOR

PART – A (2 Marks)

1. What are different data transfer schemes?

The different data transfer schemes are [M-12]

2. How is clock signal generated in 8086? What is the maximum internal clock frequency of 8086?[N-12]

The 8086 does not have on-chip clock generation circuit. Hence the clock generator chip,

8284 generates the CLK signal. The clock signal supplied by 8284 is divided by three for internal use.

The maximum internal clock frequency of 8086 is 5 MHz.

3. Write the function of queue status lines QS0 and QS1 in 8086 microprocessor. [N-12]

The function of queue status lines QS0 and QS1 in 8086 microprocessor is to indicate the

activity in the queue during previous clock cycle.

4. What is a Microprocessor? What is the difference between Microprocessor and CPU? [N-11]

A microprocessor is a multipurpose, programmable logic device that accepts binary data as input,

processes data according to the instructions and provides output in binary form. It reads binary

instructions from a storage device called memory. The CPU is the unit that includes ALU and control

unit. Apart from processing the data, the CPU controls the entire system functioning. Usually, a

microprocessor will be the CPU of a system and it is called the brain of the computer.

5. Why the program counter and the stack pointer registers are16 bits? [N-13]

Program Counter [PC] and Stack Pointer [SP] are used to hold 16-bit memory addresses. PC

stores the 16-bit memory address of the next instruction to be fetched. SP points to the beginning of

stack memory. SP can be used to temporarily store the 16-bit memory address as well as data. So,

PC and SP are 16-bit registers.

6. What are Tristate devices? [N-10]

A tri-state device is a digital device. The device is in the high state, the low state, or in a high

impedance state to prevent loading. This allows multiple circuits to share the same output line or lines.

7. Draw the flag register for 8086.

The flag register of 8086 is given below:

Conditional Flags:

CF - Carry Flag

PF - Parity Flag

AF - Auxiliary Carry Flag

ZF - Zero Flag SF - Sign Flag

OF - Overflow Flag

Control Flags:

TF – Single step Trap Flag

IF – Interrupt Enable Flag

DF – String Direction Flag

8. What is the purpose of Bus Interface Unit?

The purpose of BIU is to interface 8086 with the outside world. It provides a 16-bit bidirectional

data bus and 20-bit address bus. This unit is responsible for performing external bus operations.

Functions

1. It fetches instruction from memory.

2. It reads data from port/memory.

3. It writes data into port/memory.

4. It supports instruction queuing.

5. It provides address relocation facility

9. Write the size of the data bus and address bus of 8086?

The size of data bus and address bus of 8086 are 16-bit and 20-bit respectively.

10. What is the function of an accumulator?

Accumulator is a tri-state eight bit register. It is extensively used in arithmetic, logic, load and

store operations, as well as in input/output [I/O] operations. The result of arithmetic and logical

operations is stored in the register A. Hence, it is also identified as accumulator.

11. What is the clock frequency of 8086?

The maximum internal clock frequency of 8086 is 5 MHz.

12. What is memory segmentation?

Memory segmentation is dividing the linear memory space into “chunks” called segments.

8086 segmented memory system has four segments Code segment, Data segment, Extra segment,

and Stack segment.

13. What is pipelining?

In 8086, to speed up the execution of program, the instructions fetching and execution of

instructions are overlapped each other. This technique is known as pipelining. In pipelining,

when the n th instruction is executed, the n+1 th instruction is fetched and thus the processing speed

is increased.

14. What is meant by physical addressing in 8086?

Physical addressing is used to address 1MB memory of 8086. The 8086 memory address is 20

bits but all the registers used for memory calculation are of 16 bit length. The 20 bit physical address

is computed by summing the contents of the segment register [shifted left by 4 bits] and an effective

[offset] address. The segment register holds the upper 16 bits of the 20 bit memory address. The

effective address represents the offset from the starting address of the segment Eg: [CS x 10H ] + IP

= Physical address CS is shifted left by 4 bit and summed with IP [offset] to compute physical

address.

15. Define – Segment Override Prefix

The segment override prefix allows the programmer to deviate from the default segment. It is

an additional 8-bit code selects the alternate segment register. The code byte for the segment

override prefix as the format 001XX110. The XX represents 2 bits which are as follow: ES = 00, CS =

01, SS = 10, DS = 11.

16. How is the memory segment accessed by 8086 microprocessor? [M-15]

The memory segment accessed by 8086 microprocessor is identified by the status of the status

bits S3, S4. The Status bits S3, S4 when decoded, indicate the type of operation [memory access]

being performed and the segment register being used.

PART – B (16 Marks)

1. Draw the pin diagram of 8086 microprocessor and explain the function of each pin. [N-11]

2. Explain the internal hardware architecture of 8086 microprocessor with a

neat diagram. [N-12,M-11]

3. Explain the different data transfer schemes with examples. [N-12]

4. What are the peripheral I/O instructions?

Write its syntax. Explain the same with the timing diagram. [N-10]

5. Explain the external memory addressing of 8086.

6. Explain the interrupt architecture of 8086 microprocessor.

[M-11]

[M-12,M-11,N-10]

7. Explain maximum mode bus cycle in 8086 microprocessor. [M-12]

8. Draw and explain the signals and bus cycles in maximum mode system

configuration of 8086 microprocessor. [N-12]

9. How is 8086 configured in maximum mode and in minimum mode? Explain. [N-11]

10. Explain the various multiprocessor configurations. [N-14]

UNIT - II: 8086 SYSTEM BUS STRUCTURE

1. What is the function of the signal in 8086?

BHE signal means Bus High Enable signal. The BHE signal is made low when there is some

read or write operation is carried out. ie . When ever the data bus of the system is busy i.e.

whenever there is some data transfer then the BHE signal is made low.

2. State the significance of LOCK signal in 8086.

If 8086 is working at maximum mode, there are multiprocessors are present. If the system

bus is given to a processor then the LOCK signal is made low. That means the system bus is

busy and it cannot be given of any other processors. After the use of the system bus again the

LOCK signal is made high.

That means it is ready to give the system bus to any processor.

3. What are the functions of bus interface unit [BIU] in 8086?

[a] Fetch instructions from memory.

[b] Fetch data from memory and I/O ports.

[c] Write data to memory and I/O ports.

[d] To communicate with outside world.

[e] Provide external bus operations and bus control signals.

4. What are the two modes of operations present in 8086?

i. Minimum mode [or] Uniprocessor system

ii. Maximum mode [or] Multiprocessor system

5. What is multiprogramming?

If more than one process is carried out at the same time, then it is known as

multiprogramming. Another definition is the interleaving of CPU and I/O operations among

several programs is called multiprogramming.

To improve the utilization of CPU and I/O devices, we are designing to process a set of

independent programs concurrently by a single CPU. This technique is known as

multiprogramming

6. What is the importance of ̅̅ ̅̅ ̅̅ ̅̅ ?

Interrupt Acknowledge generated by the microprocessor in response to INTR. Causes the

interrupt vector to be put onto the data bus.

7. Under what conditions can bus contention occurs? How does a tri-state buffer help avoid

this problem?

Bus contention occurs when two outputs attempting to control the same line. It can be

avoided by tri-state buffer can be turned off

8. List the chips and their function required to design maximum mode single-processor

8086 CPU module.

1.8284A clock generator

2.8288 bus controller

3.8282/83 bus duffers

4.8286/87 address latches

9. What are the advantages of multiprocessor system?

• High level performance can be attained when parallel processing.

• Robustness can be improved by isolating system functions.

10. What are the problems occurred in multiprocessor system?

1. Bus contention

2. Interprocess communication

3. Resource sharing

11. What is Coprocessor?

The coprocessor is a processor which specially designed for processor to work under the

control of the processor and support special processing capabilities.

Example : 8087 which has numeric processing capability and works under 8086.

12. What are the basic multiprocessor configurations?

1 configuration

2. Closely Coupled . Coprocessor configuration

13. What are the schemes for establishing priority in order to resolve bus arbitration?

There are three basic bus access control and arbitration schemes

1. Daisy Chaining

2. Independent Request

3. Polling

14. Compare closely coupled and loosely coupled configurations.

Closely coupled

Loosely coupled

1. Single CPU is used

1. Multiple CPU modules are used

2. It has local bus only

2. It has local as well system bus

3. No system memory or IO

3. It has system memory and IO, shared among CPU modules

4. No bus arbitration logic required

4. Bus arbitration logic required

15. What is mean by loosely coupled multiprocessor system?

In loosely coupled multiprocessor system, each processor has a set of Input/output

devices and a large memory, where it accesses most of the instructions and data.

16. Write the advantages of loosely coupled system over tightly coupled systems?

1. More number of CPUs can be added in a loosely coupled system to improve the

system performance

2. The system structure is modular and hence easy to maintain and troubleshoot.

3. A fault in a single module does not lead to a complete system breakdown.

PART – B (16 Marks)

1. Explain the 8086 instructions used for transferring data among registers, memory, stack, and I/O devices. [N-12]

2. Write a program using 8086 instruction set to multiply a constant value with a sequence of data, from 1 to n, stored in memory. [N-12]

3. Write a program using 8086 instruction set to compute the average of „n‟ number of bytes stored in the memory. [N-12]

4. Explain data transfer, arithmetic and logical group instructions of

8086 microprocessor. [M-11,M-12]

5. Write an assembly language program for 8086 to arrange the set of numbers in ascending order and explain in detail. [M-12]

6. How are the 8086 instructions classified according to their functional categories? Explain each with an example. [N-11]

7. Write an assembly language program for 8086 to multiply two 16 bit binary numbers to generate a

32 bit result. [N-11]

8. Explain with examples the following 8086 instructions [N-11]

a. AAA

b. CBW

c. IMUL

d. INTO

9. \Write an assembly language program for 8086 to sort the array of elements in

ascending order. [M-11]

10. \Write an assembly language program for 8086 to find the largest element in an array. [M-11]

11. Explain the 8086 bit manipulation instructions with an example for each. [N-10]

12. Write an assembly language program for 8086 to convert BCD data to binary data. [N-10]

13. Explain the various assembler directives in 8086 microprocessor programming. [N-12]

14. What is the function of the ASSUME, DB, EQU, EVEN assembler directives of 8086? [N-11]

15. Explain the assembler directives ASSUME, EQU, DW, and EVEN with suitable examples.[M-11]

16. Explain the relative addressing mode and the implied addressing mode with its

syntax. Write an example for each. [N-10]

17. Design an 8086 based system in minimum mode containing 64kb of EPROM and 64kb of RAM

18. Explain the operand addressing of 8086 with examples

UNIT - III : I/O INTERFACING

1. What are the modes of operation supported by 8255?

The modes of operations supported by 8255 are:

1. I/O Mode [Input / Output mode]

a] Mode 0 – Simple I/O

b] Mode 1 – Handshaking or Strobed I/O mode

c] Mode 2 – Strobed bidirectional I/O Mode

2. BSR Mode [Bit set / reset mode ]

2. What are the enhanced features of 8254 Programmable Interval Timer compared with

8253? [N-14]

The enhanced features of 8254 Programmable Interval Timer compared with 8253 are:

1. Operating frequency 0 – 10 MHz.

2. Uses H-MOS technology.

3. Read-Back command is available.

4. Reads and writes of the same counter can be interleaved.

3. What are the functions of the scan section in 8279? [M-11]

The functions of scan counter in scan section are: 1. To scan the key matrix [keyboard] 2. To

refresh the display In encoded mode scan counter provides a binary count from 0000 to 1111

on four scan lines [SC 3 – SC 0] with active high outputs. In decoded mode scan counter

decodes least significant 2 bits of binary counts and provides 4 possible combinations on scan

lines [SC3 – SC0]: 1110, 1101, 1011, and 0111.

4. To which port of the CPU is CRT monitor and printer connected? [N-11]

The CPU is connected to CRT monitor through serial port using RS232 interface. The printer

is connected to CPU through serial interface [serial port] using RS232 interface or parallel

interface through parallel port [8255].

5. What is the operating frequency of 8279?

The required internal operating frequency of 8279 is 100 KHz to a maximum of 3 MHz.

6. What is Key debounce?

Key debounce is the minimum time that the microprocessor must wait for the key to reach

steady state when a key is pressed. Mechanical switches are used as keys in most of the

keyboards. When a key is pressed, the contact bounces back and forth and settles down only

after a small time delay [about 20 ms].

7. Compare the features of A/D converter with D/A converter. [N-11]

A/D converter D/A converter

An analog-to-digital converter [abbreviated ADC,

A/D or A to D] converts a continuous physical

quantity [usually voltage] to an equivalent digital

value.

A digital-to-analog

converter [abbreviated

DAC, D/A] translates digital

information into equivalent

Analog quantity [voltage or

current].

The basic techniques include ramp, integrating

ramp, successive approximation.

The basic technique include

decoder resistance

network.

8. Define – Resolution of ADC [M-12]

Resolution is defined as the minimum change in voltage [input] required to guarantee a

change in the output code level. The resolution Q of the ADC is equal to the LSB voltage. The

voltage resolution of an ADC is equal to its overall voltage measurement range divided by the

number of discrete values. It is expressed in volts.

EFSR is the full scale voltage range. M is the number of bits in an M bit ADC.

9. What is the function of sample and hold circuit? [M-11,N-10,M-12]

A sample and hold circuit is a circuit which samples an input signal, and holds on to its last

sampled value until the input is sampled again. Sample and hold circuits are commonly used

in analog to digital converter, communication circuits, PWM circuits, etc.

10. List out the major functions performed by CRT interface. [M-11]

The major functions performed by CRT interface are:

1. CRT terminals work on RS232 C interface.

2. CRT interface transmits and receives the binary data serially with fixed baud rate.

3. CRT interface has three terminals TXD, RXD, GND.

4. TXD is used for data transmission from CRT to microprocessor.

5. RXD is used for data transmission from microprocessor to CRT.

6. GND is used for common ground.

11. What are the functional types used in control words of 8251A ?

The control words of 8251A are divided into two functional types.

1. Mode Instruction control word 2. Command

Instruction control word Mode Instruction control word :-This defines the general

operational characteristics of 8251A.

2.Command Instruction control word:-The command

instruction controls the actual operations of the selected format like enable transmit/receive,

error reset and modem control

.

12. Write the features of mode 0 in 8255?

1. Two 8-bit ports [port A and port B] and two 4-bit ports [port C upper and lower] are

available. The two 4-bit ports can be combined used as a third 8-bit port.

2. Any port can be used as an input or output port.

3.Output ports are latched. Input ports are not latched.

4. A maximum of four ports are available so that overall 16 I/O configurations are possible.

13. What are the features used mode 1 in 8255?

Two groups – group A and group B are available for strobed data transfer.

1. Each group contains one 8-bit data I/O port and one 4-bit control/data port.

2. The 8-bit data port can be either used as input or output port. The inputs and outputs both

are latched.

3. Out of 8-bit port C, PC0-PC2 is used to generate control signals for port B and PC3=PC5

are used to generate control signals for port A. The lines PC6, PC7 may be used as

independent data lines.

14. What is the function of mode set register in 8257?

The mode set register is used for programming the 8257 as per the requirements of the

system. The function of the mode set register is to enable the DMA channels individually

and also to set the various modes of operation.

PART – B (16 Marks)

1. Explain in detail, the programming and operating modes of 8255 PPI in detail.

[N-12,M-12,M-11]

2. Draw the block diagram to interface a keyboard and a 7-segment LED using 8255 Programmable Peripheral Interface. [N-11]

3. Draw the block diagram of 8279 keyboard and display control and explain them in detail.

[N-11,N-10,M-11]

4. Describe the architecture and working of 8253 timer. Explain its modes of operation. [M-11,N-10]

5. Explain the need for sample and hold circuit and multiplexer. [N-11]

6. Explain the interfacing of any 8 bit A/D converter with an 8086 microprocessor. Write an assembly

language program for conversion. [M-12]

7. Draw and explain the operation of R-2R method of D/A converter. [N-12]

8. Explain the function of CRT terminal interface. [N-12]

UNIT - IV : MICROCONTROLLER

1. What is a microcontroller?

Microcontroller is a device which contains the microprocessor with integrated peripherals

like memory, serial ports, parallel ports, timer/counter, interrupt controller, data acquisition

interfaces like ADC, DAC.

2. What happens in power down mode of 8051 microcontroller? [M-13,M-11]

The microcontroller enters power down mode by setting the PD bit to 1. The following

happens in power down mode of 8051 microcontroller:

a) The internal clock to the entire microcontroller is stopped. However, the program is not

dead.

b) Vcc can be reduced to as low as 2V in power down mode.

c) The internal RAM gets it back up supply from RST/VPD pin.

d) Port values are not changed /overwritten in power down mode.

3. What is the size of memory systems used in 8051 microcontroller? [N-12]

The size of the memory systems in 8051 microcontroller are:

External program memory [ROM] – 64 Kbytes

External data memory [RAM] – 64 Kbytes

Internal ROM – 4 Kbytes

Internal RAM – 128 bytes

4. What is the function of RS1 and RS0 bits in the flag register of Intel 8051 microcontroller?

The function of RS1 and RS0 bits in the flag register is to select the register bank.

RS1, RS0 – Register bank select bits

RS1 RS0 Bank Selection Address

0 0 Bank 0 00h – 07h

0 1 Bank 1 08h – 0Fh

1 0 Bank 2 10h – 17h

1 1 Bank 3 18h – 1Fh

List out the applications of 8051 microcontroller.

The applications of 8051 microcontroller are

Control applications:

Office automation, home automation and industrial automation.

Embedded applications:

Since, it is single chip controller, 8051 microcontrollers are much useful in all embedded

applications like real time, wireless modes.

Network applications:

In the area of wireless networking, including LAN, MAN, and WAN.

Common applications:

Used in the measurement of frequency, reactance, voltage, current, resistance, temperature,

strain management, etc. It is also used in delay subroutine, LED display, relays, and for

interfacing with other electronic components.

5. List out the advantages of general purpose registers / register banks.

The advantages of general purpose registers are:

a) Used by programmers

b) Default power setup

c) Less processing time

6. What is PSW?

PSW [Program Status Word register] is an 8 bit register that contains the status of the

program information.

PSW consists of 4 types of flags namely carry, auxiliary carry, overflow and parity flag.

PSW is bit addressable register.

It is used to select the register bank [RS1 and RS0].

C AC F0 RS1 RS2 OV - P

7. What is the size of internal RAM and ROM of 8051?

The size of internal RAM and ROM of 8051 microcontroller are:

Internal ROM – 4 Kbytes

Internal RAM – 128 bytes

8. List out the flags available in 8051.

The flags available in 8051 are:

Four mathematical flags, Carry [CY], Auxiliary Carry [AC], Overflow Flag [OF] and Parity flag [P]

specified in PSW register.

Two general purpose flags GF0 and GF1 in the PCON register.

9. What is meant by Power On Reset in 8051?

Power On Reset in 8051 will reset the microcontroller and terminate all activities. It also

causes all values in the register to be lost. The reset pin in 8051 is pin 9. It is normally low. Upon

applying high pulse to this pin, power on reset is activated.

10. What is the need for bitwise instructions in microcontroller? [M-12]

Bitwise instructions are needed in microcontroller for the following reasons:

1. Sometimes only 1 or 2 bits of the port are to be accessed instead of entire 8 bits without

altering the rest of the bits in the port.

2. It requires discrete input and output bits, to control or detect the logic state of devices like

switches, LEDs, LCD displays and sensors for data such as temperature, humidity, light level

etc.

3. Since, microcontrollers are used in automatically controlled products and devices, such as

appliances, toys and other embedded systems.

11. What are the operand types used in 8051 microcontroller? [N-12]

The different operand types used in 8051 microcontroller are:

Immediate operand

a) Register

b) Memory

12. What are the different ways of operand addressing in 8051? [M-11]

The different ways of operand addressing in 8051 are:

a) Immediate addressing

b) Register addressing

c) Direct addressing

d) Indirect addressing

e) Relative addressing

f) Index addressing

13. What are the advantages of the register indirect addressing mode in 8051 microcontroller? [N-10]

The advantages of the register indirect addressing mode in 8051 microcontroller are:

a. It makes accessing data dynamic rather than static as in the case of direct addressing

mode.

b. Looping is possible in register indirect addressing mode.

14. Write an 8051 program to monitor P1 continuously. It should get out of the monitoring only if P1 = 63H. [N-10]

MOV P1, # 0FFh

LABEL: MOV A, P1

CJNE A, # 63,

LABEL HERE: SJMP HERE

15. List out the special function registers used for port operation in 8051? [M-12]

The special function registers used for port operation in 8051 are P0, P1, P2, and P3. Each

port are 8 bit wide which are bit addressable i.e. each bit can be set or reset by the bit instructions

[SETB for high, CLR for low] independently. The address of

1. Port 0 is 80

2. Port 1 is 90

3. Port 2 is A0

4. Port 3 is B0

16. What are the hardware and software interrupts of 8051 μc? Write its vector address. [N-11]

The hardware and software interrupts of 8051 μc are:

External hardware interrupt 0 [INT0] – 0003H

External hardware interrupt 1 [INT1] – 0013H

Timer 0 interrupt [TF0] – 000BH

Timer 1 interrupt [TF1] – 001BH

Serial port interrupt [RI or TI] – 0023H

17. How many ports are bit addressable in 8051 microcontroller? [N-11]

All the ports [Port 0 to Port 3] are bit addressable in 8051 Microcontroller.

18. List out the timers available in 8051.

The timers available in 8051 are

Timer 0 [T0] – 16 bit timer / counter

Timer 1 [T1]– 16 bit timer / counter

These two timers can be configured either as timers or event counters. They can be split into two

byte register namely TL0, TH0, TL1, and TH1.

19. What is the function of SCON register?

The SCON register is an 8 bit register used to program the start bit, stop bit, and data bit

of the data framing. The following format describes the various bits

D7 D6 D5 D4 D3 D2 D1 D0

SM0 SM1 SM2 REN TB8 RB8 TI RI

SM0 SM1 MODE

0 0 Serial Mode 0

0 1 Serial Mode 1

1 0 Serial Mode 2

1 1 Serial Mode 3

SM2: 1 – for multiprocessor communication

0 – for single processor

REN: SET/CLEAR by software to enable or disable reception

TB8: Transmit bit for serial mode 2 and 3

RB8: Receive bit for serial mode 2 and 3

20. What is the function of PCON register?

The function of PCON register is to select the power modes in 8051.The configuration

of [PCON] power control register is shown below:

SMOD: Serial baud rate modify bit

GF1 : General purpose user flag bit 1

GF0 : General purpose user flag bit 0

PD : Power down bit

IDL : Idle mode bit

PART – B (16 Marks)

1. Explain the parallel port architecture of 8051 microcontroller. [N-12]

2. Draw the pin diagram of 8051 and explain in detail, the function of each pin.

3. Draw the bit pattern of Program Status Word of 8051 and explain the significance of each bit with

examples.

4. List out the special function registers of 8051 microcontroller and explain their functions.

5. Explain the memory organization of 8051 microcontroller. [M-12]

6. Explain the architecture of 8051 microcontroller with neat diagram.

[N-11,M-11,N-10]

7. Explain the data memory structure of 8051 microcontroller. [N-11]

8. Explain the arithmetic and branching instruction of 8051 microcontroller with example. [N-12]

9. Write a program using 8051 instruction set to pack an array of unpacked BCD digits. [N-12]

10. Explain the working of program control transfer instructions of 8051 microcontroller.

11. Write an 8051 assembly language program for a lookup table application.

12. Write an assembly language program to generate square wave using on-chip timer. [M-12]

13. Assume that 5 BCD data items are stored in RAM locations starting at 40 H. Write an 8051 program to find the sum of all the numbers. The result must be in BCD. [N-10]

40 = [71]

41 = [11]

42 = [65]

43 = [59]

44 = [37]

14. Explain the logical instructions in 8051 with an example. [N-10]

15. Explain the rotate and swap instruction with an example for each. [N-10]

16. Explain in detail, the different addressing modes of 8051.

17. Explain the operations carried out when the following instructions are executed by 8051.

a) MOVX @ R 0 , A

b) MOVC A, @A + PC

c) RLC A

d) CJNE A, 50 H, L2

[M-12]

[M-12]

e) JBC 20H, L3

f) XCH A, 30 H

where, L2 and L3 are labels

25. Explain the following instructions of 8051 with examples:

a) CJNE destination, source, label

b) MUL AB

c) RRL A

d) SWAP A

e) SETB P2.0

18. Write an 8051 assembly language program to evaluate Q = [u [v + w]] + [ x . y' ] + z' ].

19. Explain the operating modes for serial port of 8051 microcontroller. [M-11]

20. Explain the operation of serial port with associated register. [N-12]

21. Write an assembly language program for 8051 to create a square wave of 66 % duty cycle on bit 3 of

port 1.

[M-11]

22. How are the timers of 8051 used to produce time delay in timer mode? [N-11]

23. Explain the interrupt structure of 8051 microcontroller. [N-11]

24. Explain the different modes of operation of timers/counters in 8051 with its associated register. [M-11]

25. Write a program in 8051 to transfer letter „A‟ serially at 4800 baud rate, 8 bit data and 1 stop bit

continuously.

26. Write a program in 8051 to transfer message „YES‟ serially at 9600 baud rate, 8 bit data and 1 stop bit continuously.

UNIT - V : INTERFACING MICROCONTROLLER

1. List the modes of Timer in 8051.

The modes of timer in 8051 are chosen with the help of two bits,viz., M0 & M1 in TMOD register.

M1 MO Mode Description of Timer

0 0 0 13-bit timer

0 1 1 16-bit timer

1 0 2 8-bit timer with auto reload

1 1 3 Split timer

2. What is the significance of C/T bit in TMOD register of 8051?

The C/T bit in the TMOD register is a selector bit for the type of operation to perform in the timer register.

HIGH in that bit indicates Counter operation and LOW in that bit indicates Timer operation.

0 Timer Operation

1 Counter Operation

3. What is the significance of TRx bit in TCON register of 8051?

TRx bit in the TCON register is used to Start / Stop the timer register for both timer and counter

operation, by setting that bit with value „1‟ or „0‟.

4. Explain the Timer operation of 8051.

In this mode, the timer register is used to generate the time delay using theclock signal applied to

the processor.An initial count is loaded in the timer register. When the timer is started, thetimer register

content gets incremented after every machine cycle. When thetimer register crosses [i.e., overflows] the

count FFFFH and goes to 0000H,the timer overflow flag in TCON register becomes set.Hence, by loading

appropriate value in the timer register, a specific timedelay can be generated using timer. One machine

cycle consists of 12 clocksignal periods and the delay is equal to count value loaded * time period of one

machine cycle

5. List the Interrupt sources in 8051.

The Six Interrupt sources in 8051 are

•RESET

•INT0, INT1

•TF0, TF1

•SPI [TI/RI]

6. What are the types of serial communication?

The serial communication can be,

•Synchronous [continuous]

•Iso-Synchronous [with regular time intervals]

•Asynchronous [with irregular time intervals]

7. Define - Baud rate

It is the speed of serial data transfer, expressed in bits/sec.The standard baud rates are110, 150,

300, 600, 1200, 2400, 4800, 9600, 19200…

8. Explain the operating mode 2 of 8051 serial ports.

In this mode 11 bits are transmitted[through TXD]or received [through RXD]:a start bit[0], 8 data

bits[LSB first],a programmable 9th data bit ,& a stop bit[1].ON transmit the 9th data bit [TB* in SCON]can

be assigned the value of 0 or 1.Or for eg:, the parity bit[P, in the PSW]could be moved into TB8.On

receive the 9th d ata bit go in to the RB8 in Special Function Register SCON, while the stop bit is ignored.

The baud rate is programmable to either 1/32 or 1/64 the oscillator frequency.

9. Explain the operating mode0 of 8051 serial ports.

In this mode serial enters &exits through RXD, TXD outputs the shift clock.8 bits are

transmitted/received:8 data bits[LSB first].The baud rate is fixed at 1/12 the oscillator frequency.

10. What are the tasks involved in keyboard interfacing?

The task involved in keyboard interfacing are sensing a keyboard interfacing are sensing a key

actuation, de bouncing the key and generating key codes[decoding the key].these task are performed

software if the keyboard is interfaced through ports and they are performed by hardware if the keyboard is

interfaced through 8279.

11. How a keyboard matrix is formed in keyboard interface?

The return lines RL0 to RL7 of 8279 are used to form the columns of keyboard matrix. In decoded

scan the scan lines SLO to SL3 of 8279 are used to form the rows of keyboard matrix. In encoded scan

mode, the output lines of external decoder are used as rows of keyboard matrix.

12. What is scanning in keyboard and what is scan time?

The process of sending a zero to each row of a keyboard matrix and reading the columns for key

actuation is called scanning. the scan time is the time taken by the processor to scan all the rows one by

one starting from first row and coming back to the first row.

13. What is scanning in display and what is the scan time?

In display devices the process of sending display codes to 7-segment LED‟S to display the led‟s one by

one is called scanning. The scan time is the time taken to display all the 7- segment LED‟S one by one,

starting from first LED and coming back to the first LED again.

PART – B (16 Marks)

1. Explain the microprocessor based traffic light control system with a neat sketch. [N-12]

2. Develop a microcontroller based traffic light controller and explain its working. [M-11,M-12]

3. Explain the microcontroller based system design with an example. [N-12]

4. Explain the working of microprocessor based stepper motor control with suitable

circuit diagram. [N-10,M-12]

5. Draw the diagram to interface a stepper motor with 8051 microcontroller and explain.

Write an 8051 assembly language program to run the stepper motor in both forward

and reverse direction with delay. 6. Write any four application of stepper motor? How is microcontroller interfaced with

stepper motor? [N-11]

7. What is the need for pulse width modulation in motor control application? Explain. [N-11]

8. List out the features of RTC device. [M-11]

9. How is a byte read from a RTC using I2C protocol? [N-11]

10. How a washing machine is controlled using microcontroller? [N-11]

11. How are microcontrollers and microprocessors used for the washing machine control

application? [N-10]

[N-10,M-11]