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MAHATRANSCO MCQs

Practice MAHATRANSCO-oriented Electronics & Telecommunication Engineering MCQs with answers and explanations for technical exam preparation. Questions are arranged in pages of up to 100.

Question 701
Microprocessors & Microcontrollers8085 Interrupts

Which 8085 interrupt is non-vectored and requires external hardware to supply an instruction during interrupt acknowledge?

  • ATRAP
  • BRST 7.5
  • CRST 5.5
  • DINTR
Report an error
Correct Answer: D. INTR
Explanation: INTR is a general-purpose non-vectored interrupt; the external device must provide an instruction, commonly an RST opcode, during interrupt acknowledge.
Reference: Standard microprocessors and microcontrollers: 8085 interrupts
Question 703
Microprocessors & Microcontrollers8085 Interrupts

The 8085 instruction EI is used to?

  • AEnable maskable interrupts
  • BDisable all clock signals
  • CEnable only TRAP
  • DErase interrupt vectors
Report an error
Correct Answer: A. Enable maskable interrupts
Explanation: EI enables the maskable interrupt system after its specified activation behavior; TRAP is non-maskable.
Reference: Standard microprocessors and microcontrollers: 8085 interrupts
Question 705
Microprocessors & Microcontrollers8085 Instructions

The 8085 instruction INX H performs which operation?

  • AIncrements HL pair by one
  • BIncrements only H by one
  • CAdds HL to accumulator
  • DLoads HL from memory
Report an error
Correct Answer: A. Increments HL pair by one
Explanation: INX operates on a 16-bit register pair, so INX H increments HL by one.
Reference: Standard microprocessors and microcontrollers: 8085 instructions
Question 708
Microprocessors & Microcontrollers8085 Logical Instructions

If A=3CH in the 8085, executing CMA produces?

  • AC3H
  • B3DH
  • CCCH
  • D00H
Report an error
Correct Answer: A. C3H
Explanation: CMA complements every accumulator bit. The one's complement of 3CH (00111100) is C3H (11000011).
Reference: Standard microprocessors and microcontrollers: 8085 logical instructions
Question 711
Microprocessors & Microcontrollers8085 Stack & Subroutines

Which 8085 instruction is used to return from a subroutine?

  • ACALL
  • BJMP
  • CRET
  • DRST
Report an error
Correct Answer: C. RET
Explanation: RET pops the saved return address from the stack into the program counter.
Reference: Standard microprocessors and microcontrollers: 8085 stack & subroutines
Question 712
Microprocessors & Microcontrollers8085 Stack & Subroutines

During a normal 8085 CALL instruction, the return address is stored on the?

  • AStack
  • BAccumulator
  • CFlag register only
  • DData bus permanently
Report an error
Correct Answer: A. Stack
Explanation: CALL pushes the return address onto the stack before transferring control to the subroutine.
Reference: Standard microprocessors and microcontrollers: 8085 stack & subroutines
Question 713
Microprocessors & Microcontrollers8085 Stack & Subroutines

In the 8085, the stack normally grows toward?

  • AHigher memory addresses
  • BLower memory addresses
  • COnly I/O addresses
  • DThe reset vector
Report an error
Correct Answer: B. Lower memory addresses
Explanation: PUSH/CALL operations decrement the stack pointer, so the 8085 stack grows toward lower memory addresses.
Reference: Standard microprocessors and microcontrollers: 8085 stack & subroutines
Question 715
Microprocessors & Microcontrollers8085 Addressing Modes

Which 8085 addressing mode is used in the instruction MVI A,32H?

  • AImmediate addressing
  • BRegister addressing
  • CDirect addressing
  • DRegister indirect addressing
Report an error
Correct Answer: A. Immediate addressing
Explanation: The operand 32H is included directly in the instruction, so MVI A,32H uses immediate addressing.
Reference: Standard microprocessors and microcontrollers: 8085 addressing modes
Question 716
Microprocessors & Microcontrollers8085 Interrupts

Which 8085 interrupt has the highest hardware priority?

  • AINTR
  • BRST 5.5
  • CRST 6.5
  • DTRAP
Report an error
Correct Answer: D. TRAP
Explanation: TRAP is the highest-priority hardware interrupt in the 8085.
Reference: Standard microprocessors and microcontrollers: 8085 interrupts
Question 717
Microprocessors & Microcontrollers8085 Addressing Modes

Which addressing mode is used by the 8085 instruction MOV A,B?

  • AImmediate
  • BRegister
  • CDirect
  • DRegister indirect
Report an error
Correct Answer: B. Register
Explanation: Both source and destination operands are CPU registers, so MOV A,B uses register addressing.
Reference: Standard microprocessors and microcontrollers: 8085 addressing modes
Question 718
Microprocessors & Microcontrollers8085 Interrupts

Which 8085 hardware interrupt is non-maskable?

  • ATRAP
  • BRST 7.5
  • CRST 6.5
  • DINTR
Report an error
Correct Answer: A. TRAP
Explanation: TRAP cannot be disabled by the normal interrupt masking mechanism and is therefore non-maskable.
Reference: Standard microprocessors and microcontrollers: 8085 interrupts
Question 719
Microprocessors & Microcontrollers8085 Interrupts

The 8085 instruction DI is used to?

  • ADisable maskable interrupts
  • BDisable TRAP permanently
  • CDecrease the accumulator
  • DDisable the address bus
Report an error
Correct Answer: A. Disable maskable interrupts
Explanation: DI disables maskable interrupts; it does not disable the non-maskable TRAP input.
Reference: Standard microprocessors and microcontrollers: 8085 interrupts
Question 720
Microprocessors & Microcontrollers8085 Timing

A T-state in a microprocessor corresponds to?

  • AOne period of the processor clock
  • BOne complete program
  • COne memory chip
  • DOne interrupt vector only
Report an error
Correct Answer: A. One period of the processor clock
Explanation: A T-state is one clock period and is the basic timing unit used to describe machine cycles.
Reference: Standard microprocessors and microcontrollers: 8085 timing
Question 723
Microprocessors & Microcontrollers8086 Architecture

The 8086 Bus Interface Unit is responsible for functions including?

  • AInstruction fetching and physical address generation
  • BOnly arithmetic multiplication
  • COnly flag comparisons
  • DOnly interrupt masking
Report an error
Correct Answer: A. Instruction fetching and physical address generation
Explanation: The BIU handles bus operations, instruction fetching, segment registers and physical-address generation.
Reference: Standard microprocessors and microcontrollers: 8086 architecture
Question 724
Microprocessors & Microcontrollers8086 Architecture

The 8086 instruction prefetch queue has a capacity of?

  • A2 bytes
  • B4 bytes
  • C6 bytes
  • D8 bytes
Report an error
Correct Answer: C. 6 bytes
Explanation: The 8086 BIU can prefetch up to six instruction bytes into its queue.
Reference: Standard microprocessors and microcontrollers: 8086 architecture
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Question 728
Microprocessors & Microcontrollers8086 Segmentation

The 8086 physical address is calculated from segment and offset as?

  • ASegment × 16 + offset
  • BSegment + offset only
  • CSegment × 256 + offset
  • DOffset × 16 + segment
Report an error
Correct Answer: A. Segment × 16 + offset
Explanation: A segment value is shifted left by four bits, equivalent to multiplying by 16, and the offset is then added.
Reference: Standard microprocessors and microcontrollers: 8086 segmentation
Question 729
Microprocessors & Microcontrollers8085 Interfacing

In the 8085, the lower-order address bus AD0-AD7 is multiplexed with the?

  • AData bus
  • BInterrupt bus
  • CClock bus
  • DPower bus
Report an error
Correct Answer: A. Data bus
Explanation: AD0-AD7 carry the low-order address during the first part of a machine cycle and data during later parts.
Reference: Standard microprocessors and microcontrollers: 8085 interfacing
Question 731
Microprocessors & Microcontrollers8085 Timing

If the 8085 READY input is low, the processor can insert?

  • AWait states
  • BExtra interrupts only
  • CReset cycles only
  • DDMA addresses only
Report an error
Correct Answer: A. Wait states
Explanation: READY allows slower memory or I/O devices to extend a bus cycle by causing the processor to insert wait states.
Reference: Standard microprocessors and microcontrollers: 8085 timing
Question 732
Microprocessors & Microcontrollers8085 Interfacing

The 8085 HOLD and HLDA signals are primarily associated with?

  • ADirect memory access
  • BSerial arithmetic
  • CSoftware interrupts
  • DBCD adjustment
Report an error
Correct Answer: A. Direct memory access
Explanation: An external DMA controller can assert HOLD; the processor responds with HLDA after relinquishing the buses.
Reference: Standard microprocessors and microcontrollers: 8085 interfacing
Question 733
Microprocessors & Microcontrollers8085 I/O Interfacing

Memory-mapped I/O in an 8085 system uses?

  • AThe memory address space and memory-type instructions
  • BOnly an 8-bit isolated port address
  • CNo address lines
  • DOnly RST instructions
Report an error
Correct Answer: A. The memory address space and memory-type instructions
Explanation: Memory-mapped I/O assigns peripheral registers addresses in the memory space, allowing memory-reference instructions to access them.
Reference: Standard microprocessors and microcontrollers: 8085 i/o interfacing
Question 734
Microprocessors & Microcontrollers8086 Architecture

The Intel 8086 is fundamentally a?

  • A16-bit microprocessor
  • B8-bit microcontroller
  • C4-bit processor
  • D32-bit DSP
Report an error
Correct Answer: A. 16-bit microprocessor
Explanation: The 8086 has a 16-bit ALU and 16-bit external data bus and is classified as a 16-bit microprocessor.
Reference: Standard microprocessors and microcontrollers: 8086 architecture
Question 738
Microprocessors & Microcontrollers8086 Segmentation

For 8086 address 1234H:0010H, the physical address is?

  • A12340H
  • B12350H
  • C12440H
  • D01244H
Report an error
Correct Answer: B. 12350H
Explanation: 1234H×10H=12340H; adding 0010H gives 12350H.
Reference: Standard microprocessors and microcontrollers: 8086 segmentation
Question 739
Microprocessors & Microcontrollers8086 Segmentation

For 8086 address 2000H:1234H, the physical address is?

  • A21234H
  • B32340H
  • C201234H
  • D03234H
Report an error
Correct Answer: A. 21234H
Explanation: 2000H×10H=20000H; adding 1234H gives 21234H.
Reference: Standard microprocessors and microcontrollers: 8086 segmentation
Question 740
Microprocessors & Microcontrollers8086 Segmentation

The maximum size of one logical 8086 segment is?

  • A16 KB
  • B32 KB
  • C64 KB
  • D1 MB
Report an error
Correct Answer: C. 64 KB
Explanation: The 16-bit offset can range from 0000H to FFFFH, so a segment can span up to 64 KiB.
Reference: Standard microprocessors and microcontrollers: 8086 segmentation
Question 744
Microprocessors & Microcontrollers8086 Addressing Modes

The 8086 instruction MOV AX,[BX] uses which addressing concept for the memory operand?

  • ARegister indirect addressing
  • BImmediate addressing
  • CImplied addressing
  • DPort addressing only
Report an error
Correct Answer: A. Register indirect addressing
Explanation: BX contains the effective offset address of the memory operand, making this a register-indirect memory reference.
Reference: Standard microprocessors and microcontrollers: 8086 addressing modes
Question 745
Microprocessors & Microcontrollers8086 Addressing Modes

In 8086 immediate addressing, the operand is?

  • AIncluded in the instruction itself
  • BAlways stored at address 00000H
  • CAlways in the stack
  • DSupplied only by an interrupt
Report an error
Correct Answer: A. Included in the instruction itself
Explanation: An immediate operand is encoded as part of the instruction.
Reference: Standard microprocessors and microcontrollers: 8086 addressing modes
Question 748
Microprocessors & Microcontrollers8051 Architecture

The classic Intel 8051 is fundamentally an?

  • A8-bit microcontroller
  • B16-bit microprocessor
  • C32-bit DSP
  • D4-bit memory controller
Report an error
Correct Answer: A. 8-bit microcontroller
Explanation: The original 8051 is an 8-bit microcontroller with an 8-bit CPU and integrated memory/peripheral resources.
Reference: Standard microprocessors and microcontrollers: 8051 architecture
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Question 753
Microprocessors & Microcontrollers8051 Registers

The 8051 DPTR register is how many bits wide?

  • A8 bits
  • B16 bits
  • C20 bits
  • D32 bits
Report an error
Correct Answer: B. 16 bits
Explanation: DPTR is a 16-bit data pointer composed of DPH and DPL.
Reference: Standard microprocessors and microcontrollers: 8051 registers
Question 755
Microprocessors & Microcontrollers8051 Interfacing

During external memory access in the 8051, Port 0 is multiplexed to carry?

  • ALow-order address and data
  • BOnly high-order address
  • COnly interrupt signals
  • DOnly serial data
Report an error
Correct Answer: A. Low-order address and data
Explanation: Port 0 serves as multiplexed AD0-AD7 for the low address byte and data bus during external-memory cycles.
Reference: Standard microprocessors and microcontrollers: 8051 interfacing
Question 756
Microprocessors & Microcontrollers8051 Interfacing

During external memory access, 8051 Port 2 commonly carries?

  • AHigh-order address byte
  • BOnly low-order data
  • CTimer overflow
  • DSerial receive data only
Report an error
Correct Answer: A. High-order address byte
Explanation: Port 2 supplies A8-A15 when the 8051 accesses external memory.
Reference: Standard microprocessors and microcontrollers: 8051 interfacing
Question 759
Microprocessors & Microcontrollers8051 Timers & Interrupts

In the 8051, the TCON register contains control/status bits associated with?

  • ATimers and external interrupts
  • BSerial baud data only
  • CProgram memory only
  • DPort 0 pull-ups only
Report an error
Correct Answer: A. Timers and external interrupts
Explanation: TCON includes timer run/overflow bits and external-interrupt control/flag bits.
Reference: Standard microprocessors and microcontrollers: 8051 timers & interrupts
Question 760
Microprocessors & Microcontrollers8051 Serial Communication

The 8051 serial port is commonly described as?

  • AFull-duplex
  • BHalf-duplex only
  • CSimplex transmit-only
  • DParallel-only
Report an error
Correct Answer: A. Full-duplex
Explanation: The 8051 serial interface can transmit and receive simultaneously, so it supports full-duplex communication.
Reference: Standard microprocessors and microcontrollers: 8051 serial communication
Question 763
Microprocessors & Microcontrollers8051 Serial Communication

In the classic 8051, the serial transmit-complete flag is?

  • ATI
  • BRI
  • CTF0
  • DIE0
Report an error
Correct Answer: A. TI
Explanation: TI is set when a serial transmission completes according to the selected serial mode.
Reference: Standard microprocessors and microcontrollers: 8051 serial communication
Question 764
Microprocessors & Microcontrollers8051 Serial Communication

In the classic 8051, the serial receive flag is?

  • ATF1
  • BRI
  • CTR0
  • DIT0
Report an error
Correct Answer: B. RI
Explanation: RI indicates that a serial data frame has been received and is ready for software handling.
Reference: Standard microprocessors and microcontrollers: 8051 serial communication
Question 765
Microprocessors & Microcontrollers8051 Interrupts

The classic 8051 provides how many standard interrupt sources?

  • A3
  • B5
  • C8
  • D16
Report an error
Correct Answer: B. 5
Explanation: The standard 8051 has five interrupt sources: external 0, Timer 0, external 1, Timer 1 and serial port.
Reference: Standard microprocessors and microcontrollers: 8051 interrupts
Question 774
Measurements & InstrumentationMeasurement Errors

An error that remains approximately constant or changes predictably and can often be corrected by calibration is generally classified as?

  • ASystematic error
  • BRandom error
  • CGross error only
  • DQuantization noise only
Report an error
Correct Answer: A. Systematic error
Explanation: Systematic errors have identifiable, repeatable causes such as calibration or environmental effects and can often be compensated.
Reference: Standard measurements and instrumentation: measurement errors
Question 775
Measurements & InstrumentationMeasurement Errors

Unpredictable variations in repeated measurements are commonly called?

  • ARandom errors
  • BSystematic errors
  • CZero errors only
  • DScale factors
Report an error
Correct Answer: A. Random errors
Explanation: Random errors vary irregularly due to uncontrollable or statistical influences.
Reference: Standard measurements and instrumentation: measurement errors
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Question 776
Measurements & InstrumentationMeasurement Errors

A gross error in measurement is most commonly associated with?

  • AHuman mistakes such as incorrect reading or recording
  • BFundamental thermal noise only
  • CPerfect calibration
  • DInfinite resolution
Report an error
Correct Answer: A. Human mistakes such as incorrect reading or recording
Explanation: Gross errors typically arise from mistakes in observation, recording, setup or calculation.
Reference: Standard measurements and instrumentation: measurement errors
Question 777
Measurements & InstrumentationCalibration

Calibration of an instrument means comparing its indication with?

  • AA known reference standard
  • BAn unknown load
  • CA random waveform
  • DOnly its own previous reading
Report an error
Correct Answer: A. A known reference standard
Explanation: Calibration establishes the relationship between an instrument's indication and values provided by suitable standards.
Reference: Standard measurements and instrumentation: calibration
Question 778
Measurements & InstrumentationInstrument Characteristics

The range of an instrument refers to?

  • AThe interval between minimum and maximum measurable input values
  • BOnly the maximum value
  • COnly the minimum value
  • DThe number of internal components
Report an error
Correct Answer: A. The interval between minimum and maximum measurable input values
Explanation: Range specifies the limits over which the instrument is intended to measure.
Reference: Standard measurements and instrumentation: instrument characteristics
Question 779
Measurements & InstrumentationMeasurement Fundamentals

Measurement is the process of comparing an unknown quantity with?

  • AAn accepted standard
  • BA random signal
  • COnly a digital display
  • DA power supply
Report an error
Correct Answer: A. An accepted standard
Explanation: Measurement determines the magnitude of a quantity by comparison with an accepted reference or standard.
Reference: Standard measurements and instrumentation: measurement fundamentals
Question 782
Measurements & InstrumentationMeasurement Fundamentals

The smallest change in input that an instrument can detect is called?

  • AResolution
  • BRange
  • CThreshold power
  • DDamping
Report an error
Correct Answer: A. Resolution
Explanation: Resolution is the smallest change in the measured quantity that can be distinguished by the instrument.
Reference: Standard measurements and instrumentation: measurement fundamentals
Question 783
Measurements & InstrumentationInstrument Characteristics

Sensitivity of an instrument is generally defined as?

  • AChange in output divided by corresponding change in input
  • BInput divided by time only
  • CMaximum input minus minimum input
  • DTrue value minus measured value
Report an error
Correct Answer: A. Change in output divided by corresponding change in input
Explanation: Sensitivity is the ratio of change in instrument output to the corresponding change in input.
Reference: Standard measurements and instrumentation: instrument characteristics
Question 786
Measurements & InstrumentationBridge Measurements

A Wheatstone bridge is widely used for precise measurement of?

  • AResistance or small resistance changes
  • BFrequency only
  • CInductance only
  • DOptical power only
Report an error
Correct Answer: A. Resistance or small resistance changes
Explanation: The Wheatstone bridge compares resistance ratios and is widely used with resistive sensors such as strain gauges.
Reference: Standard measurements and instrumentation: bridge measurements
Question 789
Measurements & InstrumentationInstrument Characteristics

Hysteresis in an instrument means that, for the same input, the output may depend on?

  • AWhether the input was approached from increasing or decreasing direction
  • BOnly the power-supply frequency
  • COnly the display color
  • DThe number of terminals
Report an error
Correct Answer: A. Whether the input was approached from increasing or decreasing direction
Explanation: Hysteresis causes different indications for the same input depending on the previous direction of input change.
Reference: Standard measurements and instrumentation: instrument characteristics
Question 790
Measurements & InstrumentationInstrument Characteristics

Instrument drift refers to?

  • AA gradual change in indication with time when the measured quantity is unchanged
  • BAn instantaneous perfect response
  • CA deliberate range selection
  • DA fixed unit conversion
Report an error
Correct Answer: A. A gradual change in indication with time when the measured quantity is unchanged
Explanation: Drift is an undesired gradual change in instrument output with time despite an unchanged input.
Reference: Standard measurements and instrumentation: instrument characteristics
Question 791
Measurements & InstrumentationTransducers

A transducer converts?

  • AA physical quantity from one form into a corresponding usable signal
  • BAC power directly into mechanical work only
  • COnly digital data into text
  • DOnly resistance into heat
Report an error
Correct Answer: A. A physical quantity from one form into a corresponding usable signal
Explanation: In instrumentation, a transducer converts a measurand into another form, commonly an electrical signal suitable for measurement or processing.
Reference: Standard measurements and instrumentation: transducers
Question 793
Measurements & InstrumentationTemperature Measurement

A thermocouple operates primarily on the?

  • ASeebeck effect
  • BHall effect
  • CPhotoelectric effect only
  • DPiezoelectric effect
Report an error
Correct Answer: A. Seebeck effect
Explanation: A thermocouple generates a thermoelectric emf due to a temperature difference between junctions, known as the Seebeck effect.
Reference: Standard measurements and instrumentation: temperature measurement
Question 795
Measurements & InstrumentationDisplacement Measurement

An LVDT is primarily used to measure?

  • ALinear displacement
  • BTemperature
  • CHumidity only
  • DOptical wavelength
Report an error
Correct Answer: A. Linear displacement
Explanation: A Linear Variable Differential Transformer converts linear displacement into an electrical output.
Reference: Standard measurements and instrumentation: displacement measurement
Question 796
Measurements & InstrumentationStrain Measurement

A strain gauge is commonly used to measure strain through a change in?

  • AElectrical resistance
  • BMagnetic permeability only
  • COptical frequency only
  • DBattery voltage only
Report an error
Correct Answer: A. Electrical resistance
Explanation: Mechanical strain changes the gauge's dimensions and therefore its electrical resistance.
Reference: Standard measurements and instrumentation: strain measurement
Question 797
Measurements & InstrumentationStrain Measurement

The gauge factor of a resistive strain gauge is defined as?

  • AFractional change in resistance divided by strain
  • BStrain divided by resistance
  • CResistance multiplied by strain
  • DVoltage divided by current
Report an error
Correct Answer: A. Fractional change in resistance divided by strain
Explanation: Gauge factor GF=(ΔR/R)/ε, where ε is mechanical strain.
Reference: Standard measurements and instrumentation: strain measurement
Question 798
Measurements & InstrumentationAnalog Instruments

A PMMC instrument is primarily suitable for direct measurement of?

  • ADC only
  • BAC only
  • CBoth AC and DC without any additional circuit
  • DMicrowave frequency only
Report an error
Correct Answer: A. DC only
Explanation: A PMMC movement responds to the average value and reverses torque with current direction, so it is inherently suited to DC. AC measurement requires rectification.
Reference: Standard measurements and instrumentation: analog instruments
Question 800
Measurements & InstrumentationDC Bridges

A Kelvin double bridge is especially suitable for measuring?

  • AVery low resistance
  • BVery high frequency
  • CCapacitance only
  • DTemperature directly
Report an error
Correct Answer: A. Very low resistance
Explanation: The Kelvin double bridge minimizes errors due to lead and contact resistance, making it suitable for low-resistance measurement.
Reference: Standard measurements and instrumentation: dc bridges
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