Category: Microcontroller Objective Questions

8051 Micro-controller Multiple Choice Questions on “ADC, DAC Interfacing”.

1. Why two pins for ground are available in ADC0804?
a) for controlling the ADCON0 and ADCON1 register of the controller
b) for controlling the analog and the digital pins of the controller
c) for both parts of the chip respectively
d) for isolate analog and digital signal

Answer: d
Clarification: Two grounds are available in ADC0804 to isolate analog signal from digital signal. This isolation provides accuracy in digital output.

2. What is the function of the WR pin?
a) its active high input used to inform ADC0804 to the end of conversion
b) its active low input used to inform ADC0804 to the end of conversion
c) its active low input used to inform ADC0804 to the start of conversion
d) its active high input used to inform ADC0804 to the start of conversion

Answer: c
Clarification: WR is active low input used to inform the ADC0804 to start the conversion process.

3. State which of the following statements are false?
a) CLK IN pin used for External Clock Input or Internal Clock with external RC element
b) INTR pin tells about the end of the conversion
c) ADC0804 IC is an 8 bit parallel ADC in the family of the ADC0800 series
d) None of the mentioned

Answer: d
Clarification: CLK IN pin is used to tell about the conversion time, INTR pin tells about the end of the conversion and ADC0804 has a resolution of 8 bits only so all three statements are true.

4. While programming the ADC0808/0809 IC what steps are followed?
a) select the analog channel, start the conversion, monitor the conversion, display the digital results
b) select the analog channel, activate the ALE signal (L to H pulse), start the conversion, monitor the conversion, read the digital results
c) select the analog channel, activate the ALE signal (H to L pulse), start the conversion, monitor the conversion, read the digital results
d) select the channel, start the conversion, end the conversion

Answer: b
Clarification: While programming the ADC0808/0809 IC firstly we need to select the channel from the A, B, C pins. Then we need to activate the ALE signal, this is needed to latch the address. Then we start the conversion from the WR pin. After monitoring the INTR pin we get to know about the end of the conversion. Then we activate the OE enable to read out data out of the ADC chip.

5. In ADC0808/0809 IC which pin is used to select Step Size?
a) Vref
b) Vin
c) Vref/2 & Vin
d) None of the mentioned

Answer: a
Clarification: Step Size is calculated by formula Vref/(2ⁿ). As ADC0808/0809 8-bit ADC value of n=8. Therefore formula becomes Vref/(2⁸) = Vref/256. If Vref = 5V then Step Size will be 5/256 i.e. 19.53mV.

6. What is the difference between ADC0804 and MAX1112?
a) ADC0804 has 8 bits and MAX1112 has 1 bit for data output
b) ADC0804 is used for adc and dac conversions whereas MAX1112 is used for serial data transmissions
c) ADC0804 has 32 bits and MAX1112 has 3 bit for data output
d) None of the mentioned

Answer: a
Clarification: ADC0804 is used for parallel ADC and MAX1112 is used for serial ADC.

7. Which of the following statements are true about DAC0808?
a) parallel digital data to analog data conversion
b) it has current as an output
c) all of the mentioned
d) none of the mentioned

Answer: a
Clarification: DAC0804 is used for parallel data to analog data conversion.

8. 8 input DAC has ________
a) 8 discrete voltage levels
b) 64 discrete voltage levels
c) 124 discrete voltage levels
d) 256 discrete voltage levels

Answer: d
Clarification: For n input DAC has 2^n discrete voltage levels.

9. INTR, WR signal is an input/output signal pin?
a) both are output
b) both are input
c) one is input and the other is output
d) none of the mentioned

Answer: c
Clarification: INTR pin tells about the end of the conversion (output) and WR pin tells us to start the conversion (input).

10. What is the function of the SCLK pin in MAX1112?
a) It is used to bring data in
b) It is used to bring data out and send in the control byte, one at a time
c) It is used to get output clock
d) It is used to get serial output

Answer: b
Clarification: SCLK is used to bring data out and send in the control byte.

AVR Microcontroller Interview Questions and Answers for freshers on “Interfacing with 8255”.

1. The 8255 is a ______ chip.
a) Input/Output
b) Analog to Digital
c) Digital to analog
d) None of the mentioned

Answer: a
Clarification: The 8255 is Input/Output (I/O) chip. It has three separate accessible ports. The 8255 chip is used to expand the I/O ports of microcontrollers.

2. Which pins of a microcontroller are directly connected with 8255?
a) RD
b) WR
c) D0-D7
d) All of the mentioned

Answer: d
Clarification: RD, WR, D0-D7 all are directly connected to the 8051 for telling the chip about the control signals and also for transferring the data.

3. Find the control word for PA= out, PB= in, PCL=out, PCH=out (Mode0)?
a) 0x02H
b) 0x82H
c) 0x83H
d) 0x03H

Answer: b
Clarification: The value that is being loaded in the control word is 10000010b for PB as an input port and all others as the output ports being operated in mode0. The hex equivalent of 10000010b → 0x82H.

4. Which pins are used to select the ports and the control register?
a) CS
b) A1
c) A0
d) All of the mentioned

Answer: d
Clarification: CS pin is an active low input pin for 8255 and it is used for selecting a chip. A0 and A1 pins are used for select ports and the control register.

5. What is the value of the control register when RESET button is set to zero?
a) 0x00H
b) 0xFFH
c) 0x11H
d) value remains the same

Answer: d
Clarification: RESET is active-high signal input into the 8255 used to clear the control register. When RESET is activated (i.e. set to high), all ports are initialized as input mode. Hence the value of the control register remains the same as it is even when the RESET button is set to zero.

6. Why MOVX instruction is being used to access the ports of the 8255?
a) because 8255 is connecting a microcontroller in memory mapped I/O configuration
b) because 8255 is used to access the external communication
c) because 8255 is used to access the data transfer
d) because 8255 is used to access the interfacing of LCD, motor etc

Answer: a
Clarification: As 8255 is connecting a microcontroller in memory mapped I/O configuration. This means that memory space used to access 8255 (i.e. 8255 is treated as external memory). MOVX instruction is used to access external memory locations.

7. What is correct about the BSR mode from below?
a) In BSR mode, only the individual bits of PORT A can be programmed
b) In BSR mode, only the individual bits of PORT B can be programmed
c) In BSR mode, only the individual bits of PORT C can be programmed
d) none of the mentioned

Answer: c
Clarification: BSR (Bit Set/Rest) mode is used to program individual bits of PORT C only.

8. How many pins of the 8255 can be used as the I/O ports?
a) 8
b) 16
c) 24
d) 32

Answer: c
Clarification: They are 3 ports available in the 8255 so 24 pins are available for the I/O ports pins.

9. 8255 is a ____ pin IC.
a) 16
b) 8
c) 40
d) 60

Answer: c
Clarification: 8255 is a 40 pin IC.

10. 8255 has handshaking capability?
a) yes
b) no
c) cant be said
d) depends on the conditions

Answer: a
Clarification: 8255 is a device that with the help of its handshaking property gets interfaced with any microcontroller.

11. The 8255 can be programmed in any of the __________
a) 2 modes
b) 3 modes
c) 4 modes
d) 5 modes

Answer: c
Clarification: 8255 can be programmed in any of the 4 modes.

MSP430 Microcontroller Question Bank on “Mixed-Signal Systems: Analog Input and Output”.

1. Which of the following is the analog to digital converter that is present in the MSP430 based processors?
a) comparator
b) successive approximation ADC
c) sigma delta ADC
d) all of the mentioned

Answer: d
Clarification: A comparator module, a successive approximation ADC module and a sigma delta ADC converters are found in the MSP based processors.

2. Higher resolution along with the slow speed is given by which ADC module?
a) comparator
b) successive approximation ADC
c) sigma delta ADC
d) all of the mentioned

Answer: c
Clarification: Higher resolution along with the slow speed is given by the sigma delta ADC module.

3. The technical terms that help us in differentiating between converters are:
a) resolution
b) accuracy
c) precision
d) all of the mentioned

Answer: d
Clarification: While selecting the converter, necessary for our work we had to take care of the factors like resolution, accuracy and precision in it.

4. The number of repeated closeness to the true value is accounted by
a) resolution
b) accuracy
c) precision
d) all of the mentioned

Answer: c
Clarification: The degree of closeness of the measured value to the actual true value is its accuracy, while on the other hand the measure of the repeated accuracy is termed as the precision.

5. Resolution is _________
a) change in measured value from the true value
b) the amount of change in the input value for the corresponding change of 1 unit in the output value
c) as the measure of the repeated accuracy
d) all of the mentioned

Answer: b
Clarification: Resolution is defined as the amount of change in the input value for the corresponding change of 1 unit in the output value.

6. The process of reduction of a continuous input to a discrete output is
a) levelling
b) signalling
c) quantization
d) converting

Answer: c
Clarification: The process of reduction of a continuous input to a discrete output is called as quantization.

7. Which of the following functions can be used for converting the nearest integer to its argument?
a) int
b) mint
c) uint
d) nint

Answer: d
Clarification: nint is the function that is priorly used for converting the nearest integer to its argument.

8. Integral nonlinearity is termed as
a) process of reduction of a continuous input to a discrete output
b) change in measured value from the true value
c) maximum deviation between this corrected staircase and the actual transfer characteristic
d) the function used in the quantization

Answer: c
Clarification: Integral nonlinearity is termed as the maximum deviation between this corrected staircase and the actual transfer characteristic.

9. The SNR_______ with the increase of the number of bits.
a) remains constant
b) goes up
c) goes down
d) goes asymmetrically

Answer: b
Clarification: The SNR goes up with the number of bits.

10. The intervals between the samples are obtained from _________
a) Fs
b) Ts
c) Us
d) Ks

Answer: b
Clarification: The intervals between the samples is obtained by Ts that is equal to 1/fs.

8051 Micro-controller Multiple Choice Questions on “Sensor Interfacing”.

1. A thermistor is a __________
a) sensor
b) adc
c) transducer
d) micro controller

Answer: c
Clarification: A thermistor is a device which is used to convert the temperature into electrical signals, so it acts as a transducer.

2. What is the difference between LM 34 and LM 35 sensors?
a) one is a sensor and the other is a transducer
b) one’s output voltage corresponds to the Fahrenheit temperature and the other corresponds to the Celsius temperature
c) one is of low precision and the other is of higher precision
d) one requires external calibration and the other doesn’t require it

Answer: b
Clarification: LM 34’s output voltage corresponds to the Fahrenheit temperature and LM 35 corresponds to the Celsius temperature.

3. An electronic device which converts physical quantity or energy from one form to another is called ______
a) Sensor
b) Transistor
c) Transducer
d) Thyristor

Answer: c
Clarification: An electronic device that converts physical quantity or energy from one form to another is called Transducer. Examples: Sensor, Speaker, Microphone, etc.

4. What is signal conditioning?
a) to analyse any signal
b) conversion or modification is referred to as conditioning
c) conversion from analog to digital is signal conditioning
d) conversion from digital to analog is signal conditioning

Answer: b
Clarification: Signal Conditioning is referred to as the conversion of a signal from one form to other, now this may be from analog to digital conditioning or digital to analog conditioning.

5. What steps have to be followed for interfacing a sensor to a microcontroller 8051?
a) make the appropriate connections with the controller, ADC conversion, analyse the results
b) interface sensor with ADC and ADC with 8051
c) interface sensor with the MAX232, send now to microcontroller, analyse the results
d) none of the mentioned

Answer: b
Clarification: For interfacing a sensor with an 8051 microcontroller, we need ADC in between because output of sensor is analog and microcontroller works on digital signals only. So whatever signal generated by the sensor is converted into its digital equivalent using ADC and equivalent digital signal is given to the microcontroller for processing.

6. LM35 has how many pins?
a) 2
b) 1
c) 3
d) 4

Answer: c
Clarification: LM35 has 3 pins.
1.Power( +5 Volts )
2.Output analog voltage
3.Ground( 0 Volts )

7. Why Vref is set of ADC0848 to 2.56 V if analog input is connected to the LM35?
a) to set the step size of the sampled input
b) to set the ground for the chip
c) to provide supply to the chip
d) all of the mentioned

Answer: a
Clarification: Vref is used to set the step size of the ADC conversion, if it is selected to 2.56 then the step size will be selected to 10mV, so for every step increase of the analog voltage an increase of 10 mV will be there.

AVR Microcontroller Questions and Answers for Experienced people on “Interfacing with RTC”.

1. RTC is used for __________
a) conversion
b) communication
c) real time and clock measurement
d) memory management

Answer: c
Clarification: RTC is a device that is basically used for all the real time clock related issues.

2. RTC chips use ______ to compute time, date when the power is off.
a) ac supply
b) generators
c) rectifiers
d) battery

Answer: d
Clarification: RTC chips require batteries in order to calculate the time and date when the power of the device is off.

3. DS12887 is known for as a ________
a) Communication device
b) Good battery device
c) RTC chip
d) All of the mentioned

Answer: c
Clarification: DS12887 is known as an RTC chip.

4. DS1307 is a parallel RTC with I2C bus.
a) true
b) false
c) cant be said
d) depends on the conditions

Answer: b
Clarification: DS1307 is a serial RTC with I2C bus.

5. DS1307 is a _______ pin IC and operates on _______ clock frequency.
a) 16, 8Mhz
b) 8, 16Mhz
c) 16, 32Mhz
d) 8, 32Khz

Answer: d
Clarification: DS1307 is a 8 pin IC and operates on a 32KHz clock frequency.

6. Vbat requires a positive signal of
a) 3V
b) 5V
c) 9V
d) 12V

Answer: a
Clarification: Vbat requires a positive signal of 3V which can be obtained through a battery.

7. In DS1307, which out of the following is correct about the SQW pin?
a) input pin
b) output pin
c) i/o pin
d) none of the mentioned

Answer:b
Clarification: In DS1307, SQW pin is an output pin. It provides a clock of frequency 1khz, 4khz, 8khz, 32khz if the pin is enabled.

8. DS1307 has a total of _______ bytes of RAM space.
a) 32
b) 64
c) 128
d) 256

Answer: b
Clarification: DS1307 has a total of 64 bytes(00-3F) of RAM space.

9. DS1307 control register has an address of _________
a) 00H
b) 03H
c) 07H
d) 10H

Answer: c
Clarification: DS1307 control register has an address of 07H.

10. What does the CH bit of the DS1307 demonstrate?
a) clock high
b) clock halt
c) clear high
d) clear halt

Answer: b
Clarification: CH bit means clock halt bit. If it is set to 1, then the oscillator gets disabled and vice versa.

MSP430 Micro-controller Multiple Choice Questions on “Comparator”.

1. Comparator_A+ is controlled by which of the following peripheral registers?
a) CACTL1
b) CACTL2
c) CACTL1 & CACTL2
d) None of the mentioned

Answer: c
Clarification: Comparator_A+ is controlled by the CACTL1 and the CACTL2 registers.

2. CAON bit is used to ___________
a) start a timer
b) start an A/D conversion
c) switch on the comparator module
d) switch on the bit transmission

Answer: c
Clarification: CAON bit is used to switch on the comparator module namely, Comparator_A+.

3. P2CA4-P2CA0 bits are used for _______
a) giving the power supply to the comparator module
b) for selecting the mode of operation of the comparator
c) for connecting the non inverting inputs to the CA0-CA2 pins
d) all of the mentioned

Answer: c
Clarification: P2CA4-P2CA0 bits are used for connecting the non inverting inputs to the CA0-CA2 pins.

4. CAREFx bits are used for _______
a) inputting a positive reference voltage
b) inputting a negative reference voltage
c) selecting the internal reference voltage
d) all of the mentioned

Answer: c
Clarification: CAREFx bits are used for selecting the appropriate reference voltage for the comparator.

5. Which of the following bits are not actually associated with the comparator module?
a) CAREFx
b) CLLDx
c) CAON
d) CAIFG

Answer: b
Clarification: CLLDx bit is related to the Timer_2 module. All others are related to the comparator module.

6. Flag CAIFG is raised,
a) at a low level triggered pulse
b) at a high level triggered pulse
c) at the falling and rising edge of the pulse
d) at the falling or rising edge of the pulse

Answer: d
Clarification: Flag CAIFG is raised, at the falling or rising edge of the pulse that is selected by the CAIES bit.

7. Setting a bit in the Port Disable register CAPD causes the circuits for the usual digital input and output buffers to be disconnected from the appropriate pin.
a) true
b) false
c) cant be said
d) depends on the conditions

Answer: a
Clarification: Setting a bit in the Port Disable register CAPD causes the circuits for the usual digital input and output buffers to be disconnected from the appropriate pin.

8. Which bit is used for exchanging the two inputs of the comparator and invert its output to compensate?
a) CAIFG
b) CASHORT
c) CAPD
d) CAEX

Answer: d
Clarification: CAEX is used for exchanging the two inputs of the comparator and invert its output to compensate.

9. Changes in Vcc changes the value of V+?
a) true
b) false
c) cant be said
d) depends on the conditions

Answer: a
Clarification: When some variation is made in the value of Vcc, in the same manner, itself the value of the V+ changes because, the voltage from the potential divider is proportional to Vcc. This changing effect can be reduced if the similar change takes place in the value of V- itself.

10. The relaxation oscillator circuit helps in _______
a) calculating the duration single RC transient
b) setting the reference voltage
c) setting the clock frequency
d) calculating the conversion speed

Answer: a
Clarification: The relaxation oscillator is a circuit that with the help of charging and discharging of an oscillator, help us in calculating the duration of the single RC transient.