Microprocessors - Short Question Answer
Here in this section of Microprocessors Short Questions Answers, We have listed out some of the important Short Questions with Answers which will help students to answer it correctly in their University Written Exam.
1. List the control and status signal of 8085 microprocessor and mention its need?
ALE (Output):
- Address Latch Enable: It occurs during the first clock cycle of a machine state and enables the address to get latched into the on chip latch of peripherals.
- The falling edge of ALE is set to guarantee set up and hold times for the address information. ALE can also be used to store the status information.
RD(Output3state):
- READ: indicates the selected memory or I/0 device is to be read and that the Data Bus is available for the data transfer.
WR (Output3state):
- WRITE: indicates the data on the Data Bus is to be written into the selected memory or I/0 location. Data is set up at the trailing edge of WR. 3stated during Hold and Halt modes.
IO/M,S0,S1:
- IO/M indicates whether input output operation or memory operation is being carried out.
- S0 and S1 indicated the type os machine cycle in progress.
READY(Input):
- If Ready is high during a read or write cycle, it indicates that the memory or peripheral is ready to send or receive data .
- If Ready is low, the CPU will wait for Ready to go high before completing the read or write cycle.
2. Specify the size of data, address, memory word and capacity of 8085 microprocessor
Size of data bus =8 bits
Size of address bus=16bit
Size of memory word=8 bit
Memory capacity=64kb
3. What is the need of ALE signal in 8085 microprocessor?
This is used to demultiplex AD0 to AD7 lines to A0-A7 and D0-D7.
The separation of address line and data line is achieved by connecting a external latch to AD0-AD7 lines and enabling the latch when ALE signal is active.
4. What is tristate logic?[june 2009]
Logic output has two states LOW and HIGH corresponding to the logic value 0 and 1.
However some output have a third electrical state that is not logical called high impedance or floating state.
In this state the output behaves as if it is not even connected to circuit except small leakage current that may flow into or out of the output pin. This state is tristate logic
5. List the five interrupt pins available in 8085[may 2010]
The five interrupt
pins available in 8085 are
·
TRAP
·
RST 7.5
·
RST 6.5
·
RST 5.5
·
INTR
6. What is stack and what is the function of stack pointer[Dec 07]
The stack is a reserved area of memory in the RAM where temporary information may be stored.
A 16 bit stack pointer is used to hold the address of most recent stack entry.
7. Define the function of parity flag and zero flag n 8085
Parity Flag (PF): This flag is used to indicate the parity of result. If lower order 8-bits of the result contains even number of 1‟s, the Parity Flag is set and for odd number of1‟s,the Parity Flag is reset.
Zero Flag(ZF) :It is set; if the result of arithmetic or logical operation is zero else it is reset.
8. What is the important control signal in 8085 microprocessor
The important signal in 8085 microprocessor are: ALE,IO/M,RD/WR.
9. Why interfacing is needed for 1/0 devices?
Generally I/O devices are slow devices. Therefore the speed
of I/O devices does not match with the speed of microprocessor. And so an
interface is provided between system bus and I/O devices.
10. Why address bus is unidirectional?
The address is an identification number used by the microprocessor to identify or access a memory location or I / O device. It is an output signal from the processor. Hence the address bus is unidirectional.
11. What are machine language and assembly language programs?
The software developed using 1's and 0's are called machine
language, programs. The software developed using mnemonics are called assembly
language programs.
12. What are the basic units of a microprocessor ?
The basic units or blocks of a microprocessor are ALU, an array of registers and control unit
13. Steps involved to fetch a byte in 8085?
The pc places the 16-bit memory address on the address bus
The control unit sends the control signal RD to enable the memory chip
The byte from the memory location is placed on the data bus
The byte is placed in the instruction decoder of the microprocessor and the task is carried out according to the instruction.
14. Define instruction cycle, machine cycle and T-state?
Instruction cycle is defined as the time required completing the execution of an instruction.
Machine cycle is defined as the time required completing one operation of accessing memory, I/O or acknowledging an external request.
T –cycle is defined as one subdivision of the operation performed in one clock period.
15. How many machine cycles does 8085 have, mention them?
The 8085 have seven machine cycles they are
- Opcode fetch
- Memory read
- Memory write
- I/O read
- I/O write
- Interrupt acknowledge
16. What is an instruction?
An instruction is a binary pattern entered through an input device to command the microprocessor to perform that specific function.
17. How many operations are there in the instruction set of 8085 microprocessor?
There are 74 operations in the 8085 microprocessor
18. List out the five categories of the 8085 instructions.Give e.g. of the instructions for each group?
Data transfer group–MOV,MVI,LXI
Arithmetic group–ADD,SUB,INR.
Logical group-ANA,XRA,CMP.
Branch group–JMP,JNZ,CALL.
StackI/O and machine control group–PUSH,POP,IN,HLT.
19. Explain the use of branch instruction and give example.
JMP instruction permanently changes the program counter. A CALL instruction leaves Information on the stacks that the original program execution sequence can be resumed.
20. Explain the purpose of the I/O instructions IN and OUT
The IN instruction is used to move data from an I/O port into the accumulator.
The OUT instruction is used to move data from the accumulator to an I/Oport.
The IN and OUT instructions are used only on microprocessor, which usea separate address space for interfacing.
21. What is the difference between the shift and rotate instructions?
A rotate instruction is a closed loop instruction. that is the data moved out at one end is put back in at the other end. The shift instruction loses the data that is moved out of the last bit locations.
22. List the four instructions which control the interrupt structure of the 8085 microprocessor?
DI(disable interrupts)
EI(enable interrupts)
RIM(read interrupt masks)
SIM(set interrupt masks)
23. Mention the categories of machine control group of instruction
The instructions of 8085 can be categorized into the following five
EI
DI
NOP
HLT
SIM
RIM
24. Explain LDA, STAANDDAA instructions
LDA copies the data byte into the accumulator from the
memory location specified by the 16-bit address.STA copies the data byte from
the accumulator in the memory location specified by 16-bitaddress. DAA changes
the content of the accumulator from binary to 4-bit BCD digits
25. Explain the different instruction format set
The instruction set is grouped into the following formats One by the instruction MOV C,A Two byte instruction MVI A,39H Three byte instruction JMP2345H
26. What is the use of addressing modes, mention the different types?[
The various formats of specifying the operands are called as addressing modes, it is used to access the operands or data. The different types are as follows
Immediate addressing
Register addressing
Direct addressing
Indirect addressing
Implicit addressing
27. Define stack and stack related instructions?
The stack is a group of memory
locations in the R/W memory that is used for the temporary storage of binary
information during the execution of the program. The stack related instructions
are PUSH and POP
28. Why do we use XRAA instruction?
The XRAA instruction is used to clear the contents of the accumulator and store the value 00H
29. Compare CALL and PUSH instructions
30. What are subroutine?
Procedures are group of instructions stored as a separate program in memory and it is called from the main program in memory and it is called from the main program when ever required.
The type of procedure depends on where the procedures are stored in memory. If it is in the same code segment as that of the main program then it is an ear procedure other wise it is a far procedure.
31. What is mean by microcontroller
A device that contains a microprocessor with integrated peripherals like memory, serial ports, parallel ports, timer/counter, interrupt controller, and data acquisition interfaces like ADC, and DAC is called a microcontroller.
32. Explain DJNZ instruction of Intel8051 microcontroller ?[
DJNZ Rn decrement the content of the register Rn and jump if not zero.
DJNZ direct, rel
Decrement the content of direct8
–bit address and jump if not zero
33. 3. State the function of RS1 and RS0 bits in the flag register of Intel8051microcontroller?
· RS1,RS0-Register bank select bits
· RS1,RS0-Bank
· Bank0
· Bank1
· Bank2
· Bank3
34. Give the alternate functions for the port pins of port3?
· RDWRT1T0
· INT1INT0TXDRXD
· RD–Read data control output
· WR–Write data control output
· T1– Timer/counter1 external input or test pin T0– Timer/counter0 external input or test pin INT1–Interrupt1 input pin
· INT0– interrupt0 input pin
· TXD–Transmit data pin
for serial port in UART
mode
·
RXD–Receive data pin for
serial port in UART mode
35. Specify the single instruction, which clears the most significant bit of Bregister of 8051,without affecting the remaining bits.
Single instruction, which clears the most significant bit of Bregister of 8051,without affecting the remaining bits, is CLRB.7.
36. What are the applications of microcontroller
·
Calculators
·
Traffic light
control system
·
Game machine
·
Military applications.
37. Give the memory size of 8051 microcontroller
The 8051 can access upto 64 kilobyte
of program memory and 64 kilo byte of data
memory.
38. Name the special functions registers available in 8051
- Accumulator
- B Register
- Program status Word.
- Stack pointer.
- Data pointer
- Port 0
- Port 1
- Port 2
- Port 3
- Interrupt priority control register. Interrupt enable control register.
39. Explain the register IE format of 8051
ü EAET2ES
ü ET1EX1ET0EX0
ü EA-Enableallcontrolbit.
ü ET2-Timer2 interruptenablebit.
ü ES- Enableserialport controlbit.
ü ET1-EnableTimer1controlbit.
ü EX1-Enableexternalinterrupt1controlbit.
ü ET0-EnableTimer0controlbit.
ü EX0-Enableexternalinterrupt0controlbit.
40. Name the five interrupt sources of 8051?
ü
The interrupt are: Vector
address
ü
External interrupt0:IE0:0003H
ü
Timers interrupt0: TF0:000BH
ü
External interrupt1:IE1:0013
ü
T imersinterrupt1:TF1:001BH
ü
Serial interrupt
ü
Receiveinterrupt:RI:0023H Transmitinterrupt:TI:0023H
41. List the features of 8051 microcontroller?
The features
are
ü Single supply
+5 volt operation using HMOS technology.
ü 4096 bytes program memory on chip (not
on 8031)
ü 128 data register banks
ü Four register mode,16-bit timer/counter.
ü Extensive Boolean
processing capabilities.
ü 64 KB external RAM size
ü 32 bi-directional individually addressable I/O lines.
ü 8 bit CPU optimized for control
applications.
42. List the addressing modes of 8051?
·
Direct addressing
·
Register addressing
·
Register in direct
addressing Implicit addressing Immediate addressing
·
Index addressing
·
Bit addressing
43. What are the modes of operation used in 8253?
Each of the three counters of 8253 can be operated in one of
the following six modes of operation.
1. Mode 0 (Interrupt
on terminal count) 2. Mode 1 (Programmable monoshot)
3. Mode 2 (Rate generator) 4. Mode 3 (Square
wave generator)
44. What is the use of 8051 chip?
· Intel‟s 8251A is a universal synchronous asynchronous receiver and transmitter compatible with Intel‟s Processors. This may be programmed to operate in any of the serial communication modes built into it.
·
This chip converts
the parallel data in to a serial stream of bits suitable
for serial transmission. It is also able to receive
a serial stream of bits and converts it in to parallel data bytes to be read by
a microprocessor.
45. What is the various programmed data transfer method?
ü Synchronous data transfer
ü Asynchronous data transfer
ü Interrupt driven
data transfer
46. What is synchronous data transfer?
It is a data method
which is used when the I/O
device and the microprocessor match in speed.
The transfer a data to or from the device ,the user program issues a suitable
instruction addressing the device.
The data transfer is completed at the end of the execution of this instruction.
47. What are the features used mode1 in 8255?
Two groups A and group B are available for stored Data transfer.
Each group contains one 8-bit data I/O port an done4-bit control/data port.
The8-bit data port can be either used as input or output port. The inputs and outputs both are latched.
48. What are the modes of operation used in 8253?[
Each of the three counters of 8253 can be operated in one of
the following six modes of operation.
ü Mode0 (Interrupt on terminal
count)
ü Mode1 (Programmable mono shot)
ü Mode2 (Rate generator)
ü Mode3 (Square wave
generator)
ü Mode4 (Software triggered strobe)
ü Mode5 (Hardware triggered strobe)
49. Give the different types of command words used in 8259A
The command words of 8259A are classified in two groups
ü Initialization command
words(ICWs)
ü Operation command
words(OCWs)
50. Define scan counter?
ü The scan counter has two modes to
scan the key matrix and refresh the display. In the encoded mode ,the counter provides
binary count that is to be externally decoded to provide the scan lines for keyboard and display
ü .In
the decoded scan mode, the counter internally decodes the least significant
2bit and provides a decoded1
out of 4scan on SL3-SL3.The keyboard and display both are
in the same mode at a time.
51. What are the modes used in keyboard modes?
- Scanned Keyboard mode with 2Key Lockout
- Scanned keyboard with N-Key Rollover.
- Scanned Keyboard Special Error Mode.
- Scanned Matrix Mode.
52. What is the use of modem control unit in 8251?
The modem control
unit handles the modem handshake
signals to coordinate the communication between
them on demand the USART.
53. List the operation modes of 8255?
ü Mode0-Simple Input/Output.
ü Mode1-Strobe Input/Output (handshake mode)
ü Mode2-Strobe bi-directional mode.
54. What is a control word?
It is a word stored
in a register (control
register) used to control the operation of a program
digital device.
55. What is the purpose of control word written to control register in 8255?
The control words
written to control
register specify an I/O function
for each I/O port.
The bit D7of
the control word determines
either the I/O functions of the BSR
function.
56. What is the size of ports in 8255?
ü Port-A:8-bits
ü Port-B:8-bits
ü Port-CU :4-bits
ü Port-CL:4-bits
57. What is an USART?
USART stands for universal Synchronous/Asynchronous
Receiver/Transmitter.It is a programmable communication interface that can communicate by using either
synchronous or asynchronous serial data.
58. Write a program using 8051 assembly language to change the data 55h stored in the lower byte of the data pointer register to AAH using rotate instruction?
MOV DPL,#55H
MOV A,DPLRL A
LABEL :SJMP Label
59. Explain the content of the accumulator after the execution of the following program segments?
MOV A,#3CH
MOVR4,#66H
ANLA,R4
A3C R466
A24
60. Explain the operating mode0 of 8051 serial ports?
In this mode serial enters & exits through RXD ,TXD output
the shift clock8 bits are transmitted or received 8 data bits(LSB first).the baud rate is
fixed at 1/12 the oscillator frequency.
61. Explain the operating mode 2 of 8051 serial ports?
In this mode
11bits are transmitted (through
TXD)or received(through RXD)A start bit(0), 8 data
bits(LSB first),a programmable 9thdata bit & a stop bit(1)
ON transmit the 9thdata
bit (TB*in SCON) can be assigned the value of 0or1.or fo reg :the parity
bit (p,in the PSW)could be movedintoTB8.
62. What is microprocessor?
A microprocessor is a processing unit of electronic devices which is including multiple transistors, diodes, register, etc electronics components. The microprocessor can operate arithmetic and logical operations as well as connect with other electronic devices for communication.
The Microprocessor made up of three terms:
- ALU(Arithmetic Logical Unit): This is used for arithmetic and logical performance which is received by memory or input data.
- Register Array: this is used for access and store the data in memory location temporarily using instruction and make the operation successful. Register array consists of Accumulator and B, C, D, E, H, L registers.
- Control Unit: Control Unit controls the data and instruction flow in the system.
The basic diagram of the microprocessor is below.
63. What is microprocessor 8085?
The 8085 (eight zero eight five) microprocessor is an 8-bit microprocessor. It is developed by Intel using NMOS technology and introduced in 1976, March. The 8085 is the version of 8080 microprocessor were added to the interrupt and serial input/output features.
The 8085 microprocessor has an 8-bit data width and 16-bit address width. This microprocessor has 60 pins. This is used for many electronic devices like oven, mobiles, etc.
64. What is interrupt in microprocessor?
The interrupt in the microprocessor is a signal which is generated by external peripherals. The external peripherals (device) send the request to the microprocessor to execute their performance and stop the current task.
After working on the external task, the microprocessor completes the previous task again.
There are five interrupt in the microprocessor which is:- RST 5.5, 6.5, 7.5, INTR, TRAP.
65. What is 8086 microprocessor?
The 8086 microprocessor is a 16-bit microprocessor. It is a developer by Intel and it is an advanced version of 8085.
This processor has a 16-bit data width, a 20-bit address width, and 1MB memory storage.
It provides a powerful instruction set. Using 8086 microprocessor make some operation like multiplication and division and so on easily.
66. What is bus in microprocessor?
The Bus is common terms in the microprocessor which is mostly used for transmission. The system of the bus is to transmit the data/information and address in binary form.
The bus is a collection of wires that means one wire per binary bit. In microprocessor have three types of the bus which is following.
- Address Bus: This is the unidirectional bus which is transmitting the address in binary form. The bus transmits data from the microprocessor to memory or input/output devices.
- Data Bus: The data bus is bidirectional and carries the data and information. This data flow both direction which means from memory/devices to microprocessor and from microprocessor to memory or input/output devices
Control Bus: This is used to control the signal and other peripherals to flow data and transfer to the required memory location
67. What is flag in microprocessor?
The Flag register is a Special Purpose Register which shows the status of the task. This is an 8-bit register but the only 5bit is used for the operation. The flag becomes set or reset after arithmetic and logical operation.
The flag register has 5 flags which are Sign flag, Zero flag, Auxiliary carry flag, Parity flag, and the Carry flag.
68. What is interfacing in microprocessor?
The microprocessor connects with many internal and external devices to process the task successfully. This procedure called interfacing in a microprocessor. In the microprocessor has i/o interfacing and memory interfacing. The connectivity of input devices (keyboard) and output devices (screen) with a microprocessor called I/O interfacing. The microprocessor accesses the memory to read the instruction code and store the data called memory interface.
69. What is register in microprocessor?
The register in the microprocessor is a temporary storage location in CPU. The register stores the data and addresses temporary for operation.
70. What is stack in microprocesso
The stack is data structure in the RAM area which is worked last in first out. It is used for operation between two registers like swap, add, etc
71. What is polling in microprocessor?
The polling method used for checking, the state of preparedness of external devices connection.
72. What is interfacing in microprocessor 8086
Interface refers to the path for communication between two components. Interfacing is of two types, memory interfacing, and I/O interfacing.
Memory Interfacing occurs when we need the microprocessor to access the memory for reading instruction codes and the data stored in the memory.
IO Interfacing indicates the various communication devices like the keyboard, mouse, printer, etc. When we need to interface the keyboard and other devices with the microprocessor by using latches and buffers. This type of interfacing is known as I/O interfacing.
73. What is subroutine in microprocessor?
The subroutine in the microprocessor is a sequence of program instructions code that performs a particular task. This is packaged as a unit and used in a particular task when needed.
A subroutine is a unit which is used in multiple times in different location. The four types of subroutine have in the microprocessor.
- Conditional Call instruction,
- Unconditional call instruction,
- Conditional return instruction,
- Unconditional return instruction.
74. What is pipelining in microprocessor?
The pipelining is an advance microprocessor technique or procedure. This is worked when the second task work before the first task. This technique used simultaneously at many processing task stages. This is helped to improve task performance. There have 5 stages of working; Instruction Fetch, Instruction Decode, Instruction Execute, Memory Access, write back Instruction.
75. What is opcode and operand in microprocessor?
The Opcode is operation codes in the microprocessor which is done addition, multiplication, etc operation.
The operand contains the data or memory location in the register. If operation worked 1+2 then 1 and 2 are operands.
76. What is macro in microprocessor?
The macro in the microprocessor is a set of instruction which is group into a single unit. The macro works less than ten instruction set.
77. What is 16 bit microprocessor?
The 16-bit microprocessor has a 16-bit data width, 20-bit address width, and 1MB memory storage. This has a powerful instruction set to do many operations. 8086 is an example of a 16-bit microprocessor.
78. What is 8 bit microprocessor?
The 8-bit microprocessor has an 8-bit data width, a 16-bit address width. The 8085 is an example of an 8-bit microprocessor.
79. What is assembler in microprocessor?
The assembler in microprocessor used to convert instruction code to machine code. The instruction code is understood for human and machine code is binary code which is understood to machine code.
80. What is data bus in microprocessor?
The data bus is bidirectional and carries the data and information. This data flow both direction which means from memory/devices to microprocessor and from microprocessor to memory or input/output devices. The data bus either 8bit or 16 bit.
81. What is memory mapping in microprocessor?
The memory mapping is used to transfer the logical address space into physical memory but sometimes physical memory is a smaller size. The microprocessor can access external memory. The memory mapping used for increased access to physical memory.
82. What is mnemonics in microprocessor?
The mnemonic in the microprocessor is acronym/abbreviation, for operation. It is used mnemonics in instruction code to make easy and suitable coding. The mnemonics are R used for the register, A for the accumulator, z for zero flags, add for addition, etc.
83. What is embedded microprocessor?
An embedded microprocessor is a computer microchip used inside many devices and electronics types of equipment. It is provides added functionality like operations and communication with the internet and other devices. It is an integrated circuit working with low power in electrical and electronic appliances as well as real-time data devices.
84. What is adc in microprocessor?
The analog signal converted into a digital signal helping by the ADC in the microcontroller. It is an 8-bit chip which has eight-channel for conversion. Analog data has binary converted into digital using logical operation.
85. What is ale in microprocessor?
The ALE is an acronym of Address Enable Latch. If pulse goes high i.e. ALE=1, it means address bus enable and pulse goes low i.e. ALE=0, it means data bus enable. The ALE controls the signal when the pulse goes high because the new task started.
86. What is buffer in microprocessor?
If data want to move one place to another place then data stored temporarily in the buffer. The address and data buffer has bidirectional data transfer. If the buffer has the least significant address then it worked unidirectional data buffer. Without loose data, the buffer can transfer data from electronic devices to microprocessors and vice versa.
87. 26) What is clock speed in microprocessor?
The rate of completing the process cycle in the microprocessor called clock speed. The clock speed measured by megahertz or gigahertz unit. 1.8 GHz processor has double clock speed than the 900MHZ processor.
88. What is the function of LOADA mem and LOADB mem?
Loaders load the all code into memory and execute the process or Task. Loader calculates the instruction and data size and makes space for memory. It initializes the many registers to execute.
89. What is dual core microprocessor?
90. How many pins in 8086 microprocessor have?
The 8086 has a 16-bit microprocessor which is 40 pins available. 16 data bus, 20 address bus, 2 ground pin, 1 reset pin, and 1 supply pin.
91. When was the first microprocessor introduced?
The first microprocessor is invented in1971. It is 4 bit Intel 4004 microprocessor.
92. When mvi is used in microprocessor?
If a task needs to take immediate input from the user then MVI instruction is used. This MVI needs 2 Machine cycles for the execution. The syntax of mvi is below.
MVI register_name, value. The value is in hexadecimal.
Example,MVI A 24H.
93. What is Microprocessor logic?
The microprocessor called also logic chips. The microprocessor does arithmetics and logical operation. The AND, OR, NOT, EXOR, has their instruction in the microcontroller. The logical operations are done by a microprocessor using a register and bus.
94. What is difference between microprocessor and microcontroller?
Difference between microprocessor and microcontroller
The microprocessor - used in the computer system. Memory and I/O device connected externally. The microprocessor actually processes the data.
The microcontroller - used in the embedded system. The memory and I/O devices have inbuilt. The microcontroller determines the process of data.
95. What is the function of program counter in 8085 microprocessor?
The program counter stores the address of the next instruction to be fetched. Thus it is used as a pointer to the instruction.