Two Marks Questions with Answers

Two Marks Questions with Answers

 

Q.1 Name any four additional hardware features available in microcontrollers when compared to microprocessors.

Ans. : The microcontroller has built-in ROM, RAM, parallel I/O, serial I/O, timer/counters and a clock circuit.

 

Q.2 Write the memory capacity of microcontroller 8051.    AU : Dec.-08

Ans. : The memory capacity of microcontroller 8051 is 64 kbytes.

 

Q.3 What are the flags available in 8051 ? AU : May-09

                     OR

What are the flags supported by 8051 microcontroller ?     AU : Dec.-19

Ans. : The flags available in 8051 are : CY (Carry flag), AC (Auxiliary carry flag), OV (over flow flag) and P (Parity flag).

 

Q.4 What is meant by SFR in 8051 ? Give an example.        AU  : May-09, 17

Ans. : The group of registers, implemented to perform special function and are located immediately above the 128 bytes of RAM are called special function registers for example, all port registers, TCOM, SCON, IE, IP, and so on.

 

Q.5 Give the memory size of 8051 microcontroller.

Ans. : The 8051 can access upto 64 kbyte program memory and 64 kbytes of data memory.

 

Q.6 Give the details of PSW of 8051. (Refer section 14.3.5)

 

Q.7 Compare microprocessor and microcontroller. (Refer section 14.1)

 

Q.8 What are the applications of 8051 microcontroller ?

Ans. : Microcontrollers are more preferred in embedded products. Some applications of microcontroller are :

• Calculators

• Accounting systems

• Game machines 

• Data acquisition systems

• Mobile systems 

• Complex industrial controllers

• Traffic light control systems

• Military applications

• Communication systems

 

Q.9 Explain the significance of SFRs in 8051 microcontroller.

Ans. : The group of registers, implemented to perform special function and are located immediately above the 128 bytes of RAM are called special function registers. They are responsible for operation of ALU, timer, serial port, parallel ports and interrupt control.

 

Q.10 What is mean by microcontroller ?

Ans. : A device which contains the microprocessor with integrated peripherals like memory, serial ports, parallel ports, timer/counter, interrupt controller, data acquisition interfaces like ADC, DAC is called microcontroller.

 

Q.11 List the features of 8051 microcontroller. (Refer section 14.2)

 

Q.12 State the function of RS1 and RSO bits in the flag register of Intel 8051 microcontroller ?

Ans. : RS1 and RS0 are bank selection bits. They are used to select working register bank of 8051 as given below :

• 0 0 Bank 0        

• 0 1 Bank 1

• 1  0 Bank 2       

• 1 1 Bank 3

 

Q.13 Give the alternate functions for the port pins of port3. (Refer Table 14.4.1)

 

Q.14 Explain the function of the PSEN pin of 8051.

Ans. :  stands for program store enable. In 8051 based system in which an external ROM holds the program code, this pin is connected to the  pin of the ROM.

 

Q.15 Explain the function of the  pin of 8051.

Ans. :  : It stands for external access. When the EA pin is connected to Vcc, program fetched to addresses 0000H through 0FFFH are directed to the internal ROM and program fetches to addresses 1000H through FFFFH are directed to external ROM/EPROM. When the  pin is grounded, all addresses fetched by program are directed to the external ROM/EPROM.

 

Q.16 Explain the 16-bit registers DPTR of 8051 or what is a function of DPTR ? AU : May-18

Ans. : DPTR : It stands for data pointer. DPTR consists of a high byte (DPH) and a low byte (DPL). Its function is to hold a 16-bit address. It may be manipulated as a 16-bit data register or as two independent 8-bit registers. It serves as a base register in indirect jumps, lookup table instructions and external data transfer.

 

Q.17 Explain the function of the SP register of 8051.

Ans. : SP : It stands for stack pointer. SP is a 8- bit wide register. It is incremented before data is stored during PUSH and CALL instructions. The stack array can reside anywhere in on-chip RAM. The stack pointer is initialized to 07H after a reset. This causes the stack to begin at location 08H.

 

Q.18 Name the special function registers available in 8051.

Ans. : The special function registers available in 8051 are :

 • Accumulator B Register

• Program Status Word.

• Stack Pointer

• Port 0

• Port 1

• Port 2

• Port 3

• Interrupt priority control register.

• Interrupt enable control register.

 

Q.19 How is stack implemented in 8051 ?

Ans. : The 8051 LIFO : Stack can reside anywhere in the internal RAM. It has 8 bit stack pointer to indicate the top of the stack using PUSH and POP instructions. During PUSH the SP is incremented by one and POP the SP is decremented by one.

 

Q.20 What is the maximum frequency of the clock signal that can be counted by 8051 counter?

Ans. : The maximum frequency of the clock signal that can be counted by 8051 counter is 1/12 x crystal frequency.

 

Q.21 What are the features of ROM and RAM in 8051 microcontroller ?

Ans. : The 8051 has 128-byte internal RAM. It is accessed using RAM address register.

The internal RAM of 8051 is organized into three distinct areas :

• Register Bank • Bit addressable • General purpose.

The 8051 has 4 kbyte of internal ROM with address space from 0000H to 0FFFH. It is programmed by manufacturer when the chip is built. This part cannot be erased or altered after fabrication. This is used to store final version of the program. It is accessed using program address register.

 

Q.22 What is the function of program counter in 8051 ?

Ans. : The 8051 has a 16-bit program counter. It is used to hold the address of memory location from which the next instruction is to be fetched.

 

Q.23 List the advantages of microcontroller over microprocessor.

Ans. : The advantages of microcontroller over microprocessor are :

• Because of built-in peripheral support they provide single chip microcontroller system.

• Less hardware required.

• Less hardware increases reliability.

• Supports internal memory which reduces access time.

 

Q.24 Which ports of 8051 are bit addressable ?

Ans. : All ports of 8051 - port 0, port 1, port 2 and port 3 are bit addressable.

 

Q.25 A given 8051 chip has a speed of 16 MHz. What is the range of frequency that can be applied to the XTAL 1 and XTAL 2 pins ?

Ans. : The range of frequencies that can be applied to the XTAL 1 and XTAL 2 pins is 1 MHz to 16 MHz.

 

Q.26 Compare the 8051, 8031 and 8751 microcontroller.  (Refer table 14.2.1)

 

Q.27  What happens in power down mode of 8051 microcontroller ?

Ans. : In the Power Down Mode (PD = 0), the CPU puts the whole chip to sleep by turning off the oscillator. In case if it is running from an external oscillator, it also gates off the path to the internal phase generators, so no internal clock is generated even if the external oscillator is still running. The on-chip RAM, however, saves its data, as long as V_CC is maintained. In this mode the only I_CC that flows is leakage, which is normally in the micro-amp range.

 

Q.28  What are on-chip resources ? List those available in the 8051 microcontroller.

Ans. : The advance microcontrollers are supported with on-chip peripherals such as program memory, data memory, parallel ports, PWM output, ADC, RTC (Real time clock), Timers/counters, Serial ports, I² C interface and so on. These are known as on-chip resources. The resources available in 8051 are :

• 4096 byte on-chip program memory

• 128 bytes on chip data memory

• 32-bit bi-directional I/O lines

• Multi-mode serial port

• Two multi-mode 16-bit timers/counters

 

Q.29  Quantify the number of register banks in 8051 and say how the CPU knows which bank is currently in use. (Refer section 14.3.5)

 

Q.30  Justify your choice between UV-EPROM and flash EPROM for an external ROM in an 8051 microcontroller application.

Ans. : Flash EPROMS can be erased electrically with selective erase facility. However, UV-EPROMS cannot be erased electrically, they need ultraviolet light source. EPROMS need around 20 minutes to erase and entire EPROM is erased at a time. Thus flash EPROM is more preferable during development stage. However, once the product is ready we can use EPROM as an external memory.

 

Q.31  What do you understand by bit addressable RAM in 8051 microcontroller ?

(Refer section 14.5.1.2)

 

Q.32  What is the function of R registers in 8051 microcontroller ?

(Refer section 14.5.1.1)

 

Q.33  What is the purpose of overflow flag in 8051 microcontroller ?

(Refer section 14.3.5)

 

Q.34  List the on-chip peripherals of 8051 microcontroller.

(Refer section 14.3)

 

Q.35  Mention the size of DPTR and stack pointer in 8051 microcontroller.

(Refer section 14.3)

 

Q.36  List the alternative functions assigned to Port 3 pins of 8051 microcontroller.

(Refer section 15.4)

 

Q.37  What are the main features of 8051 microcontroller ?

(Refer section 15.2)

 

Q.38 what is program status word of 8051?

(Refer section 14.3)

 

Q.39  Mention the purpose of  in 8051 microcontroller.

(Refer section 14.4)

 

Q.40  What is meant by PSW ?

(Refer section 14.3.5)

 

Q.41  State any four inbuilt features of 8051 microcontrollers.

(Refer section 14.2)

 

Q.42  What is the use or PSW ?

Ans. : PSW (Program Status Word) is used to determine whether or not to execute conditional instructions. In case of 8051, it is also used to select the working register bank.

 

Q.43  What is the significance of PSEN and EA pin in 8051 microcontroller ?

(Refer section 15.4)

 

 

 

 University Questions with Answers (Long Answered Questions)

 

(Regulation 2008)

Dec.-10

Q.1 Quantify the number of register banks in 8051 and say how the CPU knows which bank is currently in use. (Refer section 14.3)

Q.2 What do you understand by bit addressable RAM in 8051 microcontroller ? (Refer section 14.5)

Q.3 Discuss the internal memory organization of the 8051 microcontroller. (Refer section 14.5) [16]

Q.4 Design an 8051 based system with 16 kbytes of program ROM and 16 kbytes of data ROM.  (Refer section 14.6) [16]

Q.5 Explain in detail the different methods of memory address decoding in 8051. (Refer section 14.6) [8]

May-11

Q.6 Describe the architecture of 8051 with neat diagram. (Refer section 14.3)    [16]

Q.7 Discuss about the organization of internal RAM and special function registers of 8051 microcontroller in detail.  (Refer section 14.5) [8]

Q.8    What is the internal memory capacity of microcontroller 8051 ? (Refer section 14.5) [8]

Dec.-11

Q.9 Draw the pin diagram of 8051 microcontroller and explain its port structure. (Refer section 15.4) [8]

Q.10  Explain the program memory and data memory structure of 8051 microcontroller. (Refer section 14.5)         [8]

May-12

Q.11  Describe the architecture of 8051 with neat diagram.  (Refer section 14.3)          [16]

Q.12  Explain with a neat block diagram the architecture of 8051 microcontroller. (Refer section 14.3) [16]

Q.13 Explain program memory interfacing in 8051 microcontroller. (Refer section 14.6) [8]

Dec.-12

Q.14  Draw the data memory structure of 8051 microcontroller and explain. (Refer section 14.5) [8]

May-13

Q.15  Explain with a neat block diagram the architecture of 8051 microcontroller. (Refer section 14.3)         [16]

Dec.-14

Q.16  Explain the functional block diagram of 8051 microcontroller. (Refer section 14.3) [16]

Q.17  Explain interrupt structure of 8051 in detail.  (Refer section 14.7) [16]

 

(Regulation 2013)

May-16

Q.18  Explain with a neat block diagram the architecture of 8051 microcontroller. (Refer section 14.3)         [16]

Dec.-16

Q.19 Explain the RAM structure of 8051 microcontroller. (Refer section 14.5.1) [8]

May-17

Q.20 Explain the architecture of 8051 microcontroller with a block diagram.  (Refer section 14.3) [16]

Dec.-17

Q.21 Draw the data memory structure of 8051 microcontroller and explain. (Refer section 14.5) [7]

Q.22 Explain with block diagram, how to access external memory devices in an 8051 based system. (Refer section 14.6)     [6]

May-18

Q.23 Draw and explain the architecture of 8051 microcontroller.  (Refer section 14.3) [13]

Dec.-18

Q.24 Explain the pinouts of 8051 microcontroller. (Refer section 14.4) [13]

Q.25 Describe the timing diagram of external data memory read cycle of 8051. (Refer section 14.6.2)  [13]

 

(Regulation 2017)

Dec.-19

Q.26 With a functional block diagram, briefly discuss the architecture of the 8051 microcontroller. (Refer section 14.3) [13]

Q.27 Discuss in detail the internal data memory organization of 8051 microcontroller. (Refer section 14.5) [8]