Top 100+ Plc/microcontrollers/microprocessors Interview Questions And Answers
Question 1. What Is Plc?
Answer :
PLC are strong nation members of the laptop own family using included circuit rather than electromechanical gadgets to implement manipulate functions.
Question 2. What Are The Two Basic Sections Of Plc?
Answer :
CPU
The Input/Output interface device
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Question three. Common Plc Programming Languages?
Answer :
Ladder good judgment
Functional Block diagram
Sequential Function Chart
Question 4. How To Select A Plc (choice Criteria )?
Answer :
Cost of Hardware and Software
Reliability Flexibility Scalability
Ease of database configuration
Graphics improvement
Interlocks and batch processing
Integration of high stage utility
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Question 5. What Is Sinking Input And Sourcing Input/output?
Answer :
Sinking enter / output affords a grounded connection to the load.
Sourcing enter / output provides to the load.
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Question 6. What Are The Different Types Of Modules Used In Plc?
Answer :
Digital input
Digital Output
Analog enter
Analog output
Pulse enter
Communication module
Cpu
Question 7. Explain What Are Different Components In Plc?
Answer :
1. Input Interface
2. Memory Section
three. Central Processing Unit (CPU)
4. Programmable Language
five. Programming device
6. An output Interface
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Question 8. Explain Advantages Of Plcs Than Hard Wired Relay?
Answer :
PLCs are pretty dependable, effortlessly programmable, Small and Inexpensive, PLCs may be designed with the verbal exchange capabilities that allows you to converse with the nearby or far off laptop, They can maintain in strong environment less protection.
Question nine. Explain What Is The Programmable Language Used In Plc?
Answer :
The fashionable language program consists of Ladder Diagrams. Relay good judgment manipulate scheme is represented in Ladder diagrams. Alternative languages makes use of Boolean illustration of these manipulate schemes as base of the laptop representation.
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Question 10. Explain What Does Central Processing Unit (cpu) Of Plc Consists?
Answer :
CPU is the mind of the gadget and consists of
Microprocessor: To carryout arithematic and logical operations.
Memory: The region in the CPU in which the records is stored and reterived.
Power Supply: The electrical supply that converts the ac voltage to diverse DC working voltages.
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Question eleven. Explain What Is Scan In Plc?
Answer :
The sequential operation of the controller that is going through the ladder diagram from pinnacle to backside of the ladder. In this method it updates all the outputs similar to the inputs. SCAN takes vicinity from left to right of each rung. Usually SCAN time is in milliseconds and it's miles a non-stop process.
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Question 12. Difference Between Plcs And Computers?
Answer :
Programmable Logic Controllers (PLCs) have fundamental structure as compared to everyday general motive computer systems. A everyday pc can be converted to PLCs by using imparting a way that the computer can able to get hold of information or signal from the sector devices such as push buttons, switches and valve positions. Computer calls for a a few software program to technique the statistics acquired from the input to generate an output which determine whether or not to close or open the valve function within the process aspect.
Some of the important functions and characteristics that distinguish among the general purpose computer systems and Programmable Logic Controllers(PLCs) are given under:
PLCs are designed to function below business environments (PLCs ought to function underneath huge variety of temperature conditions, humidity and other environmental conditions). They are least suffering from the electric noise and are inherent to electrical noise Programming in PLCs is through Relay Ladder Logic or other without difficulty found out language.
PLCs comes with application language constructed in its reminiscence.
PLCs do now not contain enter and output devices inclusive of keyboards, mouse, monitor, CD drives and different difficult disks. It is in easy a self contained container with communique ports and set of terminals for input and output gadgets. Unlike computers which plays severa duties simultaneously, PLCs execute a single application in an orderly and sequential manner from first preparation to the last preparation PLCs were designed for installation and renovation through plant electricians. Programming in PLCs is straightforward (Relay Ladder Programming), it does not encompass any advanced code. Troubleshooting is less complicated and plenty of PLCs are designed to encompass fault information and written fault info on show display screen.
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Question thirteen. What Are Plcs Advantages Or Benefits?
Answer :
Higher Reliability: Once the program written and tested it could be without difficulty downloaded into different PLC's memory. It calls for lesser and less difficult wiring in comparison to standard difficult wired circuits hired. Hence reliability of the system will increase drastically with PLCs.
More Flexibility: It is less complicated to create a brand new program module or alternate an current application in PLC in comparison to tough stressed out circuitry system. These software program application modules can be modified whenever required. Use can alter the packages within the discipline and if required, security may be more suitable by using hardware interlocks including key locks and software program functions consisting of passwords.
Lower Cost: PLCs had been at first designed to replace relay manage good judgment which isn't always low cost and complex specially for massive manage circuits. With PLCs the price financial savings have been so good sized that the relay manage will become uneconomical except for a few power programs. Generally if the software includes greater than half a dozen manage relays, PLCs are least costly to put in.
Communication Capability: Communication functionality of PLC with the other controllers and computers within the device is one of the fundamental benefits in comparison to relay manipulate circuit. Functions consisting of Supervisory manipulate, records acquisition from the sphere, tracking devices and system parameters related to the field and downloading and importing of applications can be effortlessly feasible with the PLC in comparison to hardwired circuits.
Faster Response: PLCs are designed for excessive speed and for the real time packages.Response time for PLCs are a great deal smaller in comparison to relay good judgment circuits. The programmable controllers operates in real time i.E, an event taking carrying out at field will bring about execution of operation of output.
Easy to Troubleshoot: PLCs have built in diagnostics and override functions that enables the user to easily trance the software and hardware mistakes.
Question 14. What Are The Various Criteria To Choose The Microcontroller?
Answer :
The essential standards to be taken into consideration in choosing micro controllers are:
Availability of software program improvement equipment like compilers, debuggers, assemblers
Meeting the computing wishes of the mission at hand successfully at low-cost.
Wide availability
Reliable sources/manufacturers
The quantity of RAM and ROM on chip
The range of I/O pins and the timer at the chip
Power intake
Speed of the tool
Packaging
Cost in line with unit.
Question 15. List Some Of The 8051 Microcontroller Manufacturers?
Answer :
Intel
Philips
Infineon
Maxim/Dellas semiconductor
Atmel
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Question sixteen. What Is Difference Between Microprocessor And Microcontroller?
Answer :
The microprocessor has no ROM, RAM and no I/O ports on the chip itself.Whereas the microcontroller has a CPU further to a fixed amount of RAM,ROM, I/O ports and a timer all on a unmarried chip.
Question 17. List Out Some Of The Features Of The 8051?
Answer :
ROM - 4K bytes
RAM - 128 bytes
Timer - 2 no
I/O Pins - 32
Serial Port - 1
Interrupt assets - 6
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Question 18. What Are The Various Types Of Memories Used In Microcontroller/microprocessor?
Answer :
ROM - Read Only Memory
RAM - Random Access Memory
PROM - Programmable Read Only Memory
EPROM - Erasable Programmable Read Only Memory
EEROM - Electrically Erasable Programmable Read Only Memory
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Question 19. What Is Meant By Flipflop?
Answer :
A Flip-flop is a fundamental electronic circuit used for storing records in a virtual gadget.
It is a bistable device. It way it has strong states.
It has one or greater inputs and two supplement outputs.
Question 20. What Is A Bus?
Answer :
Group of traces connecting the microprocessor with different components of a pc device is known as a bus. It is a verbal exchange route over which electric signals representing binary digits ( zero, 1) are transmitted. For a single bit to transmit, one line is used. The width of the bus is number of lines which can be used to constitute that bus.
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Question 21. What Is Data Bus?
Answer :
Data Bus: Group of strains that transmit information in and out of the microprocessor is referred to as the statistics bus. Here the facts can drift in both instructions between the microprocessor and the peripheral devices. Hence the data bus is bidirectional. The width of the records bus relies upon on the architecture of the microprocessor. For an instance, an 8 bit processor can operate on 8 bits of statistics at a time and has a eight bit huge statistics bus.
Question 22. What Is Address Bus?
Answer :
Address Bus:Group of lines utilized by the microprocessor to ship the deal with of the tool or the reminiscence area which the microprocessor wishes to access.The cope with bits drift in one path, ie, from the microprocessor to the peripheral devices.Hence the deal with bus is unidirectional.The width of the deal with bus determines the most range of reminiscence locations that the microprocessor can access.
Question 23. What Is Multiplexing?
Answer :
Multiplexing:Using a unmarried bus for two exclusive functions is known as multiplexing.For an example, in 8085 microprocessor the low order eight bits of the deal with and facts are transmitted the use of AD7- AD0 traces.These lines also are used as low order deal with bus in the course of execution of commands.Thus the same lines are used for transmitting cope with and data.This is called as multiplexing.These traces are called as multiplexed address/statistics bus.
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Question 24. What Is A Microprocessor?
Answer :
Microprocessor is a program-controlled device, which fetches the instructions from memory, decodes and executes the instructions. Most Micro Processor are unmarried- chip gadgets.
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Question 25. What Are The Flags In 8086?
Answer :
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
Question 26. Why Crystal Is A Preferred Clock Source?
Answer :
Because of high stability, huge Q (Quality Factor) & the frequency that doesn’t float with aging. Crystal is used as a clock source maximum of the instances.
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Question 27. In 8085 Which Is Called As High Order / Low Order Register?
Answer :
Flag is known as as Low order register & Accumulator is called as High order Register.
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Question 28. What Is Tri-country Logic?
Answer :
Three Logic Levels are used and they may be High, Low, High impedance country. The excessive and occasional are ordinary logic tiers & excessive impedance kingdom is electric open circuit conditions. Tri-country good judgment has a 3rd line called permit line.
Question 29. What Happens When Hlt Instruction Is Executed In Processor?
Answer :
The Micro Processor enters into Halt-State and the buses are tri-stated.
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Question 30. Which Stack Is Used In 8085?
Answer :
LIFO (Last In First Out) stack is utilized in 8085.In this kind of Stack the last saved statistics may be retrieved first
Question 31. What Is Program Counter?
Answer :
Program counter holds the cope with of either the first byte of the next instruction to be fetched for execution or the deal with of the following byte of a multi byte coaching, which has no longer been completely fetched. In each the instances it receives incremented mechanically one by one because the coaching bytes get fetched. Also Program sign in continues the deal with of the following education.
Question 32. What Are The Various Registers In 8085?
Answer :
Accumulator sign up, Temporary sign in, Instruction check in, Stack Pointer, Program Counter are the numerous registers in 8085
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Question 33. What Is 1st / second / 3rd / 4th Generation Processor?
Answer :
The processor product of PMOS / NMOS / HMOS / HCMOS technology is called 1st / 2d / 3rd / 4th technology processor, and it is made of four / 8 / 16 / 32 bits.
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Question 34. Name The Processor Lines Of Two Major Manufacturer?
Answer :
High-quit: Intel – Pentium (II, III, four), AMD – Athlon. Low-end: Intel – Celeron, AMD – Duron. Sixty four-bit: Intel – Itanium 2, AMD – Opteron.
Question 35. What’s The Speed And Device Maximum Specs For Firewire?
Answer :
IEEE 1394 (Firewire) helps the most of sixty three linked gadgets with hurries up to four hundred Mbps. Where’s MBR positioned at the disk? Main Boot Record is positioned in region 0, tune zero, head 0, cylinder 0 of the primary lively partition.
Question 36. Where Does The Cpu Enhanced Mode Originate From?
Answer :
Intel’s 80386 became the primary 32-bit processor, and since the organization had to backward-support the 8086. All the cutting-edge Intel-based totally processors run inside the Enhanced mode, capable of switching between Real mode (similar to the real 8086) and Protected mode, that is the cutting-edge mode of operation.
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Question 37. How Many Bit Combinations Are There In A Byte?
Answer :
Byte incorporates 8 combos of bits.
Question 38. Have You Studied Buses? What Types?
Answer :
There are 3 forms of buses.
Address bus: This is used to carry the Address to the reminiscence to fetch both Instruction or Data.
Data bus : This is used to hold the Data from the reminiscence.
Control bus : This is used to carry the Control indicators like RD/WR, Select and many others.
Question 39. What Is The Maximum Clock Frequency In 8086?
Answer :
5 Mhz is the Maximum clock frequency in 8086.
Question forty. What Is Meant By Maskable Interrupts?
Answer :
An interrupt that may be became off via the programmer is referred to as Maskable interrupt.
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Question 41. What Do You Mean By The Term Embedded Controllers?
Answer :
The devices that has all of the functional blocks on chip, which includes this system and records memory and there's no external facts/address bus provided. For instance, ATMEL89C2051.
Question forty two. Discuss The Advantages Of Microcontroller Over Microprocessor In Control Applications?
Answer :
The first primary advantage is that the ALUs may be assembled together horizontally to form computers that may take care of very large information at a time. Another gain is bit slice layout that makes use of possible bipolar chip generation this is very rapid.
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Question forty three. What Are Risc And Cisc Processors?
Answer :
RISC chips requires lesser hardware implementations, which makes them simpler to design and consequently lesser prices of manufacturing.
Question 44. Discuss The Criteria For Selecting A Micro-controller Device?
Answer :
It should have ram and rom to support its in-built capabilities. It ought to have +5v supply, should be fast and have to have programmable and information reminiscence.
Question 45. Discuss The Advantages And Disadvantages Of Harvard And Von Neuman Architectures?
Answer :
Harvard structure uses separate recollections for application and information reminiscence whereas Von Neuman makes use of same application and data reminiscence.Therefore Harvard is faster compared to other one.
Question 46. Name 2 Register That Consists Of sixteen Bit?
Answer :
Program counter
Data pointer
Question forty seven. Name Few General Purpose Registers?
Answer :
Accumulator, B-sign up, R0- R7
Question 48. What Are Sfr?
Answer :
The 128 bytes of on-chip additional RAM locations from 80H to 0FFH are reserved for the special functions and consequently those are referred to as as unique function check in.
Question forty nine. Can An Rc Circuit Be Used As Clock Source For 8085?
Answer :
Yes, it may be used, if an correct clock frequency isn't always required. Also, the component cost is low in comparison to LC or Crystal
Question 50. Which Interrupt Has The Highest Priority?
Answer :
TRAP has the very best priority
Question fifty one. What Are Hardware Interrupts?
Answer :
TRAP, RST7.5, RST6.Five, RST5.Five, INTR
Question fifty two. What Does Quality Factor Mean?
Answer :
The Quality aspect is also defined, as Q. So it's far a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.
Question fifty three. What Is Stack Pointer?
Answer :
Stack pointer is a special cause 16-bit check in inside the Microprocessor, which holds the address of the pinnacle of the stack.
Question 54. What Are Level-triggering Interrupt?
Answer :
RST 6.5 & RST five.5 are degree-triggering interrupts.
Question fifty five. What Is The Difference Between Primary & Secondary Storage Device?
Answer :
In primary storage tool the garage potential is restrained. It has a volatile reminiscence. In secondary storage tool the storage potential is greater. It is a nonvolatile reminiscence. Primary gadgets are: RAM / ROM. Secondary devices are: Floppy disc / Hard disk.
Question 56. Name 5 Different Addressing Modes?
Answer :
Immediate
Direct
Register
Register indirect
Implied addressing modes
Question fifty seven. What Is Clock Frequency For 8085?
Answer :
3 MHz is the most clock frequency for 8085.
Question fifty eight. What Is The Difference Between 8086 And 8088?
Answer :
The BIU in 8088 is 8-bit facts bus & 16- bit in 8086.Instruction queue is four byte long in 8088and 6 byte in 8086.
Question 59. Give Example For Non-maskable Interrupts?
Answer :
Trap is known as Non-Maskable interrupts, that's used in emergency condition.
Question 60. What Is Sim And Rim Instructions?
Answer :
SIM: is Set Interrupt Mask. Used to mask the hardware interrupts.
RIM: is Read Interrupt Mask. Used to test whether or not the interrupt is Masked or now not.
