AU Solved Paper 90205 - set 16

AU Solved Paper 90205

December - 2019

Microprocessors & Microcontrollers

Semester-V (EEE) - Regulation 2017

 

Time: Three Hours]

[Maximum Marks: 100

 

Answer ALL Questions

PART A - (10 × 2 = 20 Marks)

Q.1 List two major differences between INTR and the other hardware interrupts. (Refer Two Marks Q.10 of Chapter 4)

Q.2 Does the 8085 support externally initiated operations. If yes, how? (Refer Two Marks Q.31 of Chapter - 1)

 

Q.3 Illustrate the changes made to the content of registers during the execution of the instruction LXI B, 4000H.

Ans.: BH = 40H and BL = 00H

 

Q.4 State the advantages of subroutine. (Refer Two Marks Q.43 of Chapter - 2)

Q.5Can single bit of a port be accessed in 8051 ? If yes, how? Give an example. (Refer section 15.6)

Q.6 What are the flags supported by 8051 microcontroller? (Refer section 14.3.5)

Q.7 Differentiate programmed I/O and interrupt driven I/O. (Refer Two Marks Q.11 of Chapter - 4)

Q.8 Why an interface is needed in between CPU and input-output devices? (Refer Two Marks Q.10 of Chapter - 7)

Q.9 Write a program to load the accumulator with the value 82H and complement the accumulator 700 times. (Refer Two Marks Q.7 of Chapter 3)

Q.10 List any four applications of 8051 to automation systems. (Refer Q.10 of Dec.-2018)

 

PART B - (5 × 13 = 65 Marks)

Q.11 a) With a functional block diagram, briefly discuss the architecture of the 8085 microprocessor. (Refer section 1.2)

OR

b) Draw the timing diagram of the instruction MVI B, 45. Assume the memory address of the opcode and the data is 2000H and 2001H respectively. = 2DH)] [Refer Fig. 5.4.10 (Note: Replace data 08H with (45)

12 a) i) Differentiate RAL and RLC instruction. (Refer section 2.2.4) [3]

ii) Write an assembly language program for 8085 microprocessor to count even numbers in series of 10 numbers.

(Refer similar lab experiment 3.1.18) [10]

Example :

b) i) Briefly describe stack pointer register. (Refer section 1.2.1) [3]

ii) Briefly discuss the different types of addressing modes supported by the 8085 microprocessor with examples. (Refer section 2.3) [10]

Q.13 a) With a functional block diagram, briefly discuss the architecture of the 8051 microcontroller, (Refer section 14.3)

OR

b) i) Summarize the similarities and differences between 8085 and 8051. [5]

Ans. :

ii) Discuss in detail the internal data memory organization of 8051. microcontroller. (Refer section 14.5) [8]

Q.14 a) i) Interface 8255 with 8085 microprocessor and write an assembly language program to display 99 in Port A, 1's complement of 99 in Port B and 2's complement of 99 in Port C. Assume the port addresses are 30H, 31H and 32H for ports A, B and C respectively. [5]

Ans. : For interfacing: Refer section 8.7

When all ports to be configured in output mode control word in 80H.

Program

MVI A, 80H ; Load control word

OUT 33H ; Send control word to control register

MVI A, 99H ; Load 99H in A

OUT 30H ; Send to port A

CMA ; 1's complement A

OUT 31H ; Send to port B

ADI 01H ; Add 1 to get 2's complement

OUT 32H ; Send to port C

ii) Describe the operating modes and control words of 8255. (Refer sections 8.4 and 8.5) [8]

OR

b) With a functional block diagram, briefly discuss the architecture of the 8259 programmable interrupt controller. (Refer section 9.5)

Q.15 a) Show how to interface a stepper motor to 8051 microcontroller. Also, write an assembly language program to demonstrate control of direction and speed of stepper motor rotation. (Refer section 17.4)

OR

Show how to interface a servo motor to 8051 microcontroller. Also, explain the working principle to control a servo motor with angle rotations (Not in new syllabus)

 

PART C - (1 × 15 = 15 Marks)

Q.16 a) Show how to interface a 8×8 matrix keyboard to the 8051 microcontroller and discuss in detail the various stages for detection and identification of key activation by a microcontroller. Also, write an assembly language program to detect and identify the processed key. (Refer section 17.1.2)

OR

b) Show how to interface a Digital to Analog Converter (DAC) with 8085 microprocessor and write an assembly language program to generate a square waveform. Also, discuss in detail the successive approximation technique for the process of conversion of analog signal to digital data. (Refer section 13.3)

Ans.:  In this technique, the basic idea is to adjust the DAC's input code such that its output is within ± 1 / 2 LSB of the analog input V_i to be A/D converted. The code that achieves this represents the desired ADC output.

• The successive approximation method uses very efficient code searching strategy called binary search. It completes searching process for n-bit conversion in just n clock periods.

• Fig. 2 shows the block diagram of successive approximation A/D converter. It consists of a DAC, a comparator and a Successive Approximation Register (SAR).

• The external clock input sets the internal timing parameters. The control signal Start of Conversion (SoC) initiates an A/D conversion process and end of conversion signal is activated when the conversion is completed.

Operation:

• The searching code process in successive approximation method is similar to weighing an unknown material with a balance scale and a set of standard weights.

• Let us assume that we have 1 kg, 2 kg and 4 kg weights (SAR) plus a balance scale (comparator and DAC). Now we will see the successive approximation analogy for 3-bit ADC.

• The analog voltage Vin is applied at one input of comparator. On receiving start of conversion signal (SOC) successive approximation register sets 3-bit binary code 1002 (b2 = 1) as an input of DAC. This is similar process of placing the unknown weight on one platform of the balance and 4 kg weight on the other.

• The DAC converts the digital word 100 and applies it equivalent analog output at the second input of the comparator.

• The comparator then compares two voltages just like comparing unknown. weight with 4 kg weight with the help of balance scale.

• If the input voltage is greater than the analog output of DAC, successive approximation register keeps b₂ = 1 and makes b₁ = 1 (addition of 2 kg weight to have total 6 kg weight) otherwise it resets b₂ = 0 and makes b₁ = 1 (replacing 2 kg weight). The same process is repeated for b₁ and b₀. The status of b_o, b₁ and b₂ bits gives the digital equivalent of the analog input.

• The time for one analog to digital conversion must depend on both the clock's period T and number of bits n. It is given as,

T_C = T (n + 1)

where T_C = Conversion time

T = Clock period

n = Number of bits