8051 Microcontroller Question & Answers June 6, 2022 By WatElectronics This article lists 100 8051 Microcontroller MCQs for engineering students. All the 8051 MC Questions & Answers given below include a hint and a link wherever possible to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up on the fundamentals of the 8051 Microcontroller. 8051 has many instructions and functions like 8-bit ALU, timers, and counters which are 16-bit each, the on-chip ram of 128 0r 256 bytes, has an 8-bit data bus, 32-bit address bus, and holds ROM memory size 64kb each. 8051 holds a Harvard architecture, has 16 special function registers, two accumulators A, B, and Program status word has 7 bits where 0-bit is a parity bit and 1st bit is a user-defined bit, 2nd is overflow flag bit, 3rd-4th pins are register select pins, 5th pin is a flag bit holds 0 value. B-register is used to multiply and divide instructions where 256 bits are addressable. Operands like MOV-which moves the operand, SUB-which subtracts the operand, INC-which increments the operand, DEC-which decrements the operand. CJNZ, JMP, ORL, ANL, ADDC-which adds the operand with carrying bit, XCH-which exchanges the accumulator values, SUBB-which subtracts and borrows, DJNZ. 8051 is a 40-pin dual inline package that has four ports Port 0, Port 1, Port 2, and Port 3. 1). Mostly ____ bit is an 8051 microcontroller. 2 4 6 8 None Hint 2). 8051 is set up with a ____ pins dual inline combination. 39 40 38 24 None Hint Read more about 8051 Microcontroller. 3). Read-only memory holds _____ kb of storage in 8051. 2 4 6 8 None Hint 4). Random access memory holds _____ bytes of storage in 8051. 124 128 324 126 None Hint 5). The chip crystal oscillator holds a frequency of ____ MHz in 8051. 6 12 18 24 None Hint Read more about Crystal Oscillator. 6). How many timers exist in 8051 which is 16-bit? 0 1 2 3 None Hint 7). Pins from _____ are known as Port1 in 8051 Microcontroller. 1-8 1-6 1-7 0-1 None Hint 8). Pin 9 represents ______ pin in 8051 microcontroller. Start Reset Ground None Of These None Hint 9). Pins from _____ are known as Port3 in 8051 Microcontroller. 10-15 12-17 10-17 10-16 None Hint 10). Port 3 provides some tasks such as interrupts, timers, and _____ communications. Parallel Serial Hybrid Comparator None Hint 11). Pins 18 and 19 combine an ____ crystal to form a structured clock. Internal Inside External None of these None Hint 12) Pins from _____ are known as Port2 in 8051 Microcontroller. 21-28 21-29 20-28 20-29 None Hint 13). Expand PSEN Full form _____? Program Storage Enable Point Store Enable Plaint Storage Enable None Of These None Hint 14).Expand EA full form ______? External amplifier External amplitude External access input None of these None Hint 15).Expand ALE full form ______? Address latch enable Address light external Address latch eternal None of these None Hint 16).The circuit is powered/supplied by pin____ of 8051 MC. 30 40 50 38 None Hint 17). PSEN explains a wave from the outmost /exterior program _____? Wavelength Timing Memory Switch None Hint 18). Pins from _____ are known as Port0 in 8051 Microcontroller. 32-39 32-37 31-37 31-38 None Hint 19). Using port 2, the higher sequence _____ signals are multiplied. Signal Bus Data Bus Address Bus None Of these None Hint 20). Using port 0, the lower sequence _____ signals are multiplied. Signal Bus Data Bus Address Bus Address-Data bus None Hint 21). Address latch enable use to distribute data through____ signal of the port. Signal Bus Data Bus Address Bus Address-Data bus None Hint 22). 8051 has four ___ ports which are of 8-bit each. Input-Output Input Output None of these None Hint 23). ______ are used to connect to input-output ports. Peripheral Devices Memory Devices Circuits Timers None Hint 24). Logic 1 is meant for ____ of power supply. 0V 2V 5V 10V None Hint 25). Logic 0 is meant for ____ of power supply. 0V 2V 5V 10V None Hint 8051 Microcontroller Interview Questions and Answers 26). 0V is nothing but connected to _____? Ground Voltage Amplifier Actuator Oscillator None Hint 27). When output pins are arranged at logic 0, then each pin holds a current of ___? 5mA 10mA 15mA None of these None Hint 28). If pins are arranged as inputs, then it provides a ____ current at pull-up resistors. Strong Weak Null None of these None Hint 29). If every port of 8-bits is active, then the total current is switched to _____? 5mA 10mA 15mA 1.5mA None Hint 30). If every port of 32-bits is active, then the total current is switched to ____. 60mA 71mA 72mA 75mA None Hint 31)._______ which alters the program for some time temporary. Interrupts Timers Actuators Shifters None Hint 32). How many interrupt signals exist in 8051? 2 3 4 5 None Hint 33).______ register is used to empower and impair interrupts. Interrupt Enable Interrupt Disable None of these None Hint 34). For enabling the interrupts _______ register is set to one. Disable Enabling Hybrid Shift None Hint 35). For disabling the interrupts _______ register is set to zero. Disable Enabling Hybrid Shift None Hint 36). IE.5 and IE.6 pin is empty because it is reserved for _____? Inbuilt Future Use Outside Inside None Hint 37).To enable/disable _______ interrupt, the ES pin is used. Parallel Address Bus Buses Serial port None Hint 38).To enable/disable _____interrupt, the ET1 pin is used. Timer 1 overflow Timer 0 overflow Buses Serial port None Hint 39).To enable/disable _____interrupt, the ET0 pin is used. Timer 1 overflow Timer 0 overflow Buses Serial port None Hint 40). To enable/disable ______ interrupt1, the EX1 pin is used. Hybrid Multiple External Internal None Hint 41). To enable/disable external interrupt0, the ___ pin is used. Rx Tx EX0 EX1 None Hint 42). Altering the priority levels of interrupts is done using the _____ register. Internal Interrupt External Interrupt Interrupt Enable Interrupt Priority None Hint 43). IP.5 and IP.6 pins which are reserved used for the______? Initial Future Current None of the above None Hint 44). PS pin represents the priority level of _____ interrupt. Serial Port Timers Buses Signals None Hint 45). PT0 represents the priority level of _____ interrupt. Serial port Timer0 Timer1 Parallel port None Hint 46). PT1 represents the priority level of _____ interrupt. Serial Port Timer0 Timer1 Parallel port None Hint 47). PX0 represents the 0 priority level of _____ interrupt. External Internal Hybrid Serial None Hint 48). PX1 represents the priority level 1 of _____ interrupt. Internal External Hybrid Serial None Hint 49). Expand PSW full form _______? Processor status word Processor status word Processor status works None of these None Hint 50). Expand SP full form _____? Store Pointer Stack Pointer Store Point Store Package None Hint 8051 Microcontroller MCQs for Exams 51). Memory which is used to add the program is called ______ memory. Program Process Shift Right None Hint 52). Program memory is also known as _____ memory. Process Shift Code Right None Hint 53). Program will be regained when the power is switched off is called _____memory. ROM RAM EPROM SRAM None Hint 54). For all of the arithmetic operations and logical instructions, _____ is used. Multiplier Shifter Accumulator None of these None Hint 55). In the B register, R0-R7 are used to store address and data _____? Bus Signals Instructions Transfer None Hint 56). DPTR is used to operate data in _____ addressing mode. Same Different Unique None Of These None Hint 57). Data point register holds ____ bit address. 12 14 16 18 None Hint 58). DPL of the data point register holds ____ byte of data. High Low Null None of these None Hint 59). DPH of the data point register holds a ____ byte of data. High Low Null None of these None Hint 60). Program counter holds ___ of register? 12 bit 16 bit 14 bit 20 bit None Hint 61). PSW register is also called as _____ register? Program Shift Flag Right None Hint 62). Even though PSW holds an 8-bit register only ____ bits are used? 2 4 6 8 None Hint 63). PSW register holds flags which are called _____ flags? Shift Conditional Unidirectional Bidirectional None Hint 64). First bank register starts from one location and stops at the ____H location? Two Three Fifth Seventh None Hint 65). Second bank register starts from the eighth location and stops at the ____H location? Fifth Fourth Sixth Seventh None Hint 66). Third bank register starts from the tenth location and stops at the ____ H location? Fifteenth Sixteenth Seventeenth None Of these None Hint 67). Final bank register starts from the eighteenth location and stops at the ____ H location? 2F 1F 3F 4F None Hint 68). In 8051, the stack holds ____ bits wide? 2 4 6 8 None Hint 69). Stack holds data from 00 to __ H? 1F FF DF 0F None Hint 70). 8051 depends on a ____ architecture? ARM Harvard Von Newman Both a and c None Hint 71). 8051 uses different methods to access data called ______? Accessing mode Addressing mode Re-Addressing mode None of these None Hint 72). There exist _____ types of addressing modes for microcontrollers? 2 3 4 5 None Hint 73). RI/TI is a _____ interrupt? Data Transfer Serial Communication External Internal None Hint 74). In 8051, the on-chip ROM contains _____ of memory? 2kb 4kb 8kb 16kB None Hint 75). In 8051, ____ interrupt sources exist? 2 5 6 8 None Hint 8051 Microcontroller Quiz Questions and Answers. 76). Pin 9 in microcontroller _____ is used for resetting and stopping the activity. RESET GND Vcc V0 None Hint 77). Pin 3.1 acts as a ______ pin which is used to transfer the data? Parallel Serial Hybrid Side by side None Hint 78). Pin 3.0 acts as a serial pin that is used to ______ the data? Transfer Move Receive None of these None Hint 79). P3.6 is a _____ pin that writes data to the outermost memory? Read Move Send Write None Hint 80). Pin 40 is a ____ pin for supplying power with 5v? GND Vcc 0.5 1 None Hint 81). INC Operand defines the ______ operation? Read Write Increment Decrement None Hint 82). DEC Operand defines the ______ operation? Read Write Increment Decrement None Hint 83). ADD Operand defines the ______ operation? Subtraction Addition Multiplication None Of these None Hint 84). SUB will ______ from the resultant value? Addition Subtract Multiply Divide None Hint 85). INC and DEC will work as ______ instructions? Addition Subtract Logical Transfer None Hint 86). MOV operand _____ values from one register to another. Moves Receives Stands Stop None Hint 87). XCH Operand in which exchanging the accumulator and _____ takes place. Operands Operator Sum Sub None Hint 88). SUBB defines, there is no subtraction without _______? Adding Borrowing Moving Stops None Hint 89). SETB bit in 8051 which _____ the specified bits? Moves Transfers Add Sets None Hint 90). CLR bit in 8051 which _____ the specified bits. Moves Transfers Clears Sets None Hint 91). CPL bit in 8051 which _____ the specified bits? Complements Transfers Clears Sets None Hint 92). JBC in 8051 defines it as it jumps if the bit is set and ____ the bit? Moves Clears Stands None Of these None Hint 93). LJMP and LCALL address instructions are of ____bits? 12 14 16 18 None Hint 94). XRL performs ______ ex-or into accumulator? Arithmetic Logical Model Sight None Hint 95). ORL operand performs logical ____ operations? AND NAND NOR OR None Hint 96). ANL operator performs logical ____ operations? AND NAND NOR OR None Hint 97). DJNZ defines _____ the operand and it jumps to the system. Increment Decrement Move Add None Hint 98). CJNE defines _____the operand and it jumps to the system. Move Add Compare Subtract None Hint 99). Addition and subtraction bits are instructions which ____ the PSW Flags? Moves Sets Adds Subtracts None Hint 100). Increment and decrement bits are instructions that don't ____ the PSW Flags? Moves Sets Adds Subtracts None Hint For More MCQs Microcontrollers Questions & Answers Please fill in the comment box below. Time's up
