ma viva bank

7/27/2019 MA Viva Bank

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1) What is the difference between microprocessor and microcontroller?

The microprocessor are general purpose computer with CPU, memory addressingcircuit, interrupt handling circuits and its models vary in data size from 4 to 32 bits.

The microcontrollers are special purpose digital controller with above features of microprocessor plus it has timer parallel and serial I/O and internal RAM and ROM.

2) Describe the internal Ram of 8051?

The internal RAM of 8051 is generally 128 bytes. It is classified as 4 register banksof 8 registers each. 16 byte addressable at bit level & 8 bytes of general purpose datamemory.

3) How many timers are available in 8051?

There are two 16 bit timer/counter option. They are T0 and T1.

4) What are the different control registers in 8051?

The following control register are present in 8051:TCON, TMOD, SCON, PCON, IP, & IE.

5) How many interrupt sources are made available in 8051?

There are two external & three internal interrupt sources.

6) Which register of PSW are used to select register bank?

The register R50 and R51 are used to select register bank.

7) Which flag is used in arithmetic instruction?

The overflow flag (OV) is used in arithmetic instruction.

8) Which flag is used for BCD arithmetic?

The auxiliary carry flag is used BCD arithmetic.

9) The carry flag is used for which instruction?

The carry flag is used for arithmetic, jump, rotate and Boolean instruction.

10) What is the position of the port during power on or power reset?



The port P0 to P3 will be high during power ON condition.

11) List the different register priority wise?

The register are listed as per the following ranking based on priority to response an

interfacing.1) IE0 2) TF0 3) IE1 4) TF1 5) SERIAL (T1 OR R1)

12) Name the features of 8051?

The following are the 3 main features of 8051.128 byte RAM, $k ON-CHIP ROM and 48 bit I/O ports.

13) What is the major difference between 8051 and 8052 microcontroller?

The 8052 has everything that the 8051 has. It has an extra timer and the on-chip ROM

is 8k instead. The RAM in 8052 is 256 byte instead of 128 bytes.

14) List different 8-bit register of 8051?

A, B, R0 TO R7, SP.

15) List 16 bit register of 8051?

DPTR, PC.

16) Why is assembly language caused as low level language?

The assembly language is called as low level language as it directly deals with theinternal structure of CPU.

17) What is a compiler?

A compiler is a program that translates high level language into machine code.

18) Which directive is used for ASCII string?

The ‘DB’ directive is used for ASCII string.

19) What is the advantage in using the ‘EQU’ directive to define a constant

value?

If the value are to be changed later, it can be easily done once in one place instead of every occurrence.

20) What is the flag register in 8051 called as?



The flag register 8051 is called as program status word i.e., PSW.

21) What is the size of flag register in 8051?

The size of flag register in 8051 is 8 bit.

22) Which bits of the PSW registers are users definable?

D1 and D5 i.e., PSW.1 and PSW.5 are user definable.

23) When is the carry flag (CF) set?

The carry flag is set whenever there is carry out from the d7 bit. This flag is affectedafter.

24) Is it possible to have immediate data as destination?

No, it is not possible to have immediate data as destination.

25) What should be the number in the register RP?

It must be always the ram address.

26) Which register are used for indirect addressing?

Only register R0 and R1 may be used for indirect addressing.

27) All external data moves must involve which register?

All external data moves must involve the accumulator.

28) How many bytes can register RP address?

Rp can address 256 bytes.

29) How many bytes can DPTR address?

DPTR can address 64k bytes.

30) What happens to the PC before it is added to A to form the final address of

the code byte?

The PC is incremented by 1 to point to the next instruction.



31) What precaution one has to take to handle the subtract operation?

The carry flag is set to 0 if is not to be included as part of the subtraction operation.

32) Which register bank is used if we alter RS0 and RS1 of the PSW by thefollowing 2 instruction?

SETB psw.3

SETB psw.4

The register bank 3 is used.

33) Name 16 bit register in 8051?

PC and DPTR.

34) What is the result of the following code and where it is kept?MOV A, #15H

MOV R2, #13H

ADD A, R2

The result is 28H and is stored in accumulator.

35) In the ADD instruction, when CY is raised?

The CY is raised or set whenever there is a carry out from the D7 bit.

36) In the ADD instruction, when is AC flag set?

If there is a carry from D3 to D4 during an ADD or SUB operation, this bit is set,otherwise it is cleared.

37) Which flag is used to perform BCD arithmetic?

The AC flag is used to perform the BCD arithmetic.

38) In the 8051, which register bank conflict with the stack?

Bank1.

39) In ‘JZ = NEXT’ which register content is checked to see if it zero?

The accumulator.



40) What do the mnemonic LCALL and ACALL stand for?

LCALL is termed as Long Call.ACALL is termed as Absolute Call.

41) Show the instruction to enable EX0 and Timer0 interrupts?

MOV IE, # 1000011b

42) Which pin of the 8051 is assigned to the external hardware interrupt INT?

Port pin P3.3 which is pin 13 on the 40 pin DIP package is assigned as external hardwareinterrupt.

43) What address in the interrupt vector table is assigned t the INT1 and Timer1

interrupts?

0013 for INT1 and 001b for timer1.

44) What address in the interrupt vector table is assigned to timer 0?

0000Bh is assigned as address to timer 0.

45) Which bit of IE belong to the Timer interrupt? Show how both are enabled?

Bits D1 and D3 belong to the timer interrupts. They are enabled by the instruction: MOVIE # 10001010b

46) What address in the interrupt vector table is assigned to INT0 and INT1? What

at=re their pin number?

The address are 0003h and 0013h. pins are 12(p3.2) and 13(p3.3).

47) which bit of ie register belong to the external hardware interrupt? Show how

both are enabled.

Bits d0 and d2 belong to the external hardware interrupt and are enabled by theinstruction MOV IE,#10000101B.

48) Assume that IE bit for external hardware interrupt EX1 is enabled and is active

low explain how these interrupt works when it is activated?

Upon application of a low pulse(min 4 machine cycle wide), to pin p3.3, the 8051. isinterrupted in whatever it is doing and jump to ROM location 00BH to execute theISR.



49) Explain the role that each of the two bits TCON.0 and TCON.2 play in the

execution of external interrupts 0?

TCON.0 is set to high to make INT0 an edge triggered. If INT 0 is edge triggered(i.e

TCON.0 is set ) whenever high to low pulse is applied to the INT0 is latched and kept by the TCON.0 bit by making TCON.2 high. While the ISR for INT0 is beingserviced,TCON.2 stays high. No matter how many times a high to low pulse isapplied to pin INT0.

Upon the execution of the last instruction of the ISR, which is RETI the TCON.2 bit iscleared indicating that the INT0 pin can respond to another interrupt.

50) What address in the interrupt vector table is assign to the serial interrupt?

23H is the address assigned for serial interrupt.

51) How are interrupts better than Polling?

In polling the processor needs to continuously monitor the i/o device whether it is readyor not. This continuous monitoring of the device may lead to undue waste of time.Whereas the device may interrupt the processor as and when required ,in the mean timethe processor my carry on with some other piece of work.

52) Explain the working of the enable pin of the LCD

The data written on to the data pins is taken in only when a high to low pulse is given onthis pin or to understand the data written comes into action only when high to low pulseis given.

53) What is the role of SBUF register during serial communication?

Any data that needs to be transmitted or received is passed through the SBUF register. thedata being transmitted is moved to SBUF and the data received through serialcommunication is collected in SBUF.

54) A stepper with a step angle of 5 degrees has how many steps per revolution?

a) 144b) 72c) 48d) 24

Answer is 72.

55) What is the total number of steps needed to rotate one complete rotation?



The total number of steps are 180 steps * 20 = 360

56) What is the purpose of LM336 Zener diode around pot setting Vref/2?

The purpose of LM336 Zener diode around pot setting Vref/2 is to overcome any

fluctuation in power supply.

57) LM34 provides __10mv_ __ for each degree of _ Fahernheit,_(Fahernheit, Celsius) temperature.

58) LM35 provides _10mv__ for each degree of _ Celsius __(Fahernheit, Celsius) temperature.

59) A stepper with a step angle of 7.5 degrees has how many steps per revolution?

a) 144b) 72

c) 48d) 24

Answer is 48

60) A stepper with a step angle of 15 degrees has how many steps per revolution?

a) 144b) 72c) 48d) 24

Answer is 24

61) A stepper with a step angle of 2.5 degrees has how many steps per revolution?

a) 144b) 72c) 48d) 24

Answer is 144

62) What will be the order of 4 step sequence of stepper motor if we start with 0110?

a) 1,2,4b) 4,1,2c) 1,4,2d) 2,1,4

Answer is 4,1,2.




a) 1,2,4b) 4,1,2c) 1,4,2d) 2,1,4

Answer is 1,2,4.


a) 1,2,4b) 4,1,2c) 1,4,2d) 2,1,4

Answer is 2,1,4.

65) What is the direction (out, in) for each of following pins of ADC 808/809.

A) A,B,C B) SC C)EOC.

The direction for A,B,C is in, for SC is also in and for EOC is out .

66) In ADC804, the INTR signal is

a) Input Signal b) Output signal

It is output signal

67) Which pin of ADC804 indicates end of conversion?

a) INTR b) CS c) RD d) Vcc.

The pin of ADC804 which indicates end of conversion is INTR.

68) Which pin of ADC804 indicates start of conversion?

a) INTR b) CS c) RD d) Vcc.

The pin of ADC804 which indicates start of conversion is RD

69) Both the ADC 804 and ADC 808 are ___8____ bit converter

70) For an ADC804 chips, find the step size of Vref values

a) Vref/2 = 1.28 Volt b) Vref/2 = 1 Volt

The step size for 1.28 Volt is Vref = 2.56/ 256 = 10The step size for 1Volt is Vref = 2/ 256 = 7.81

71) Is self clocking present in ADC 808/809?

No



72) On what factor speed of conversion depends?

Speed of conversion depends on frequency of clock connected to the clock pin.

73) What is the relation between digital output voltage and analog input voltage andstep size?

Dout = Vin/ step-size.

74) DAC 808 is an __ 8 ___ bit D to A Converter

75) To get the full scale output what should be the inputs for DAC?

All inputs are high.

76) Assume that R=5k and Iref= 2mA, calculate Vout for 10011001?

Iout = 2 mA * 153/ 255 = 1.195 mA.

Vout = 1.195 * 5 = 5.975

77) Assume that R=5k and Iref= 2mA, calculate Vout for 11001000?

Iout = 2 mA * 200/ 256 = 1.562 mA

Vout = 1.562 * 5 = 7.8125.

78) What will be the value of column of keypad matrix if no key is pressed?

The value of column of keypad matrix if no key is pressed is all 1’s

79) To detect the key press which of following is grounded?

A) All rows B) One row at a time C) both (A) and (B)

Answer is A

80) To identify the key press which of following is grounded?

A) All rows B) One row at a time C) both (A) and (B)

Answer is B

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