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Friday, May 16, 2008
8085 Microprocessor Important Interview Questions - 1
8085 microprocessor questions
What are the various registers in 8085? - Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .
In 8085 name the 16 bit registers? - Stack pointer and Program counter all have 16 bits.
What are the various flags used in 8085? - Sign flag, Zero flag, Auxillary flag, Parity flag, Carry flag.
What is Stack Pointer? - Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack.
What is Program counter? - Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.
Which Stack is used in 8085? - LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.
What happens when HLT instruction is executed in processor? - The Micro Processor enters into Halt-State and the buses are tri-stated.
What is meant by a bus? - A bus is a group of conducting lines that carriers data, address, & control signals.
What is Tri-state logic? - Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.
Give an example of one address microprocessor? - 8085 is a one address microprocessor.
In what way interrupts are classified in 8085? - In 8085 the interrupts are classified as Hardware and Software interrupts.
What are Hardware interrupts? - TRAP, RST7.5, RST6.5, RST5.5, INTR.
What are Software interrupts? - RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.
Which interrupt has the highest priority? - TRAP has the highest priority.
Name 5 different addressing modes? - Immediate, Direct, Register, Register indirect, Implied addressing modes.
How many interrupts are there in 8085? - There are 12 interrupts in 8085.
What is clock frequency for 8085? - 3 MHz is the maximum clock frequency for 8085.
What is the RST for the TRAP? - RST 4.5 is called as TRAP.
In 8085 which is called as High order / Low order Register? - Flag is called as Low order register & Accumulator is called as High order Register.
What are input & output devices? - Keyboards, Floppy disk are the examples of input devices. Printer, LED / LCD display, CRT Monitor are the examples of output devices.
Can an RC circuit be used as clock source for 8085? - Yes, it can be used, if an accurate clock frequency is not required. Also, the component cost is low compared to LC or Crystal.
Why crystal is a preferred clock source? - Because of high stability, large Q (Quality Factor) & the frequency that doesn?t drift with aging. Crystal is used as a clock source most of the times.
Which interrupt is not level-sensitive in 8085? - RST 7.5 is a raising edge-triggering interrupt.
What does Quality factor mean? - The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.
What are level-triggering interrupt? - RST 6.5 & RST 5.5 are level-triggering interrupts.
8086 Interview Questions 2008 Recent - 2
8086 interview questions
What are the flags in 8086? - In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
What are the various interrupts in 8086? - Maskable interrupts, Non-Maskable interrupts.
What is meant by Maskable interrupts? - An interrupt that can be turned off by the programmer is known as Maskable interrupt.
What is Non-Maskable interrupts? - An interrupt which can be never be turned off (ie.disabled) is known as Non-Maskable interrupt.
Which interrupts are generally used for critical events? - Non-Maskable interrupts are used in critical events. Such as Power failure, Emergency, Shut off etc.,
Give examples for Maskable interrupts? - RST 7.5, RST6.5, RST5.5 are Maskable interrupts
Give example for Non-Maskable interrupts? - Trap is known as Non-Maskable interrupts, which is used in emergency condition.
What is the Maximum clock frequency in 8086? - 5 Mhz is the Maximum clock frequency in 8086.
What are the various segment registers in 8086? - Code, Data, Stack, Extra Segment registers in 8086.
Which Stack is used in 8086? - FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.
What are the address lines for the software interrupts? -
RST 0
0000 H
RST1
0008 H
RST2
0010 H
RST3
0018 H
RST4
0020 H
RST5
0028 H
RST6
0030 H
RST7
0038 H
What is SIM and RIM instructions? - SIM is Set Interrupt Mask. Used to mask the hardware interrupts. RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.
Which is the tool used to connect the user and the computer? - Interpreter is the tool used to connect the user and the tool.
What is the position of the Stack Pointer after the PUSH instruction? - The address line is 02 less than the earlier value.
What is the position of the Stack Pointer after the POP instruction? - The address line is 02 greater than the earlier value.
Logic calculations are done in which type of registers? - Accumulator is the register in which Arithmetic and Logic calculations are done.
What are the different functional units in 8086? - Bus Interface Unit and Execution unit, are the two different functional units in 8086.
Give examples for Micro controller? - Z80, Intel MSC51 &96, Motorola are the best examples of Microcontroller.
What is meant by cross-compiler? - A program runs on one machine and executes on another is called as cross-compiler.
What are the address lines for the hardware interrupts? -
RST 7.5
003C H
RST 6.5
0034 H
RST 5.5
002C H
TRAP
0024 H
Which Segment is used to store interrupt and subroutine return address registers? - Stack Segment in segment register is used to store interrupt and subroutine return address registers.
Which Flags can be set or reset by the programmer and also used to control the operation of the processor? - Trace Flag, Interrupt Flag, Direction Flag.
What does EU do? - Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.
Which microprocessor accepts the program written for 8086 without any changes? - 8088 is that processor.
What is the difference between 8086 and 8088? - The BIU in 8088 is 8-bit data bus & 16- bit in 8086.Instruction queue is 4 byte long in 8088and 6 byte in 8086.
Microprocessor x86 Interview Questions - 3
x86 interview questions
What is a Microprocessor? - Microprocessor is a program-controlled device, which fetches the instructions from memory, decodes and executes the instructions. Most Micro Processor are single- chip devices.
Give examples for 8 / 16 / 32 bit Microprocessor? - 8-bit Processor - 8085 / Z80 / 6800; 16-bit Processor - 8086 / 68000 / Z8000; 32-bit Processor - 80386 / 80486.
Why 8085 processor is called an 8 bit processor? - Because 8085 processor has 8 bit ALU (Arithmetic Logic Review). Similarly 8086 processor has 16 bit ALU.
What is 1st / 2nd / 3rd / 4th generation processor? - The processor made of PMOS / NMOS / HMOS / HCMOS technology is called 1st / 2nd / 3rd / 4th generation processor, and it is made up of 4 / 8 / 16 / 32 bits.
Define HCMOS? - High-density n- type Complimentary Metal Oxide Silicon field effect transistor.
What does microprocessor speed depend on? - The processing speed depends on DATA BUS WIDTH.
Is the address bus unidirectional? - The address bus is unidirectional because the address information is always given by the Micro Processor to address a memory location of an input / output devices.
Is the data bus is Bi-directional? - The data bus is Bi-directional because the same bus is used for transfer of data between Micro Processor and memory or input / output devices in both the direction.
What is the disadvantage of microprocessor? - It has limitations on the size of data. Most Microprocessor does not support floating-point operations.
What is the difference between microprocessor and microcontroller? - In Microprocessor more op-codes, few bit handling instructions. But in Microcontroller: fewer op-codes, more bit handling Instructions, and also it is defined as a device that includes micro processor, memory, & input / output signal lines on a single chip.
What is meant by LATCH? - Latch is a D- type flip-flop used as a temporary storage device controlled by a timing signal, which can store 0 or 1. The primary function of a Latch is data storage. It is used in output devices such as LED, to hold the data for display.
Why does microprocessor contain ROM chips? - Microprocessor contain ROM chip because it contain instructions to execute data.
What is the difference between primary & secondary storage device? - In primary storage device the storage capacity is limited. It has a volatile memory. In secondary storage device the storage capacity is larger. It is a nonvolatile memory. Primary devices are: RAM / ROM. Secondary devices are: Floppy disc / Hard disk.
Difference between static and dynamic RAM? - Static RAM: No refreshing, 6 to 8 MOS transistors are required to form one memory cell, Information stored as voltage level in a flip flop. Dynamic RAM: Refreshed periodically, 3 to 4 transistors are required to form one memory cell, Information is stored as a charge in the gate to substrate capacitance.
What is interrupt? - Interrupt is a signal send by external device to the processor so as to request the processor to perform a particular work.
What is cache memory? - Cache memory is a small high-speed memory. It is used for temporary storage of data & information between the main memory and the CPU (center processing unit). The cache memory is only in RAM.
What is called ?Scratch pad of computer?? - Cache Memory is scratch pad of computer.
Which transistor is used in each cell of EPROM? - Floating ?gate Avalanche Injection MOS (FAMOS) transistor is used in each cell of EPROM.
Differentiate between RAM and ROM? - RAM: Read / Write memory, High Speed, Volatile Memory. ROM: Read only memory, Low Speed, Non Voliate Memory.
What is a compiler? - Compiler is used to translate the high-level language program into machine code at a time. It doesn?t require special instruction to store in a memory, it stores automatically. The Execution time is less compared to Interpreter.
Which processor structure is pipelined? - All x86 processors have pipelined structure.
What is flag? - Flag is a flip-flop used to store the information about the status of a processor and the status of the instruction executed most recently
What is stack? - Stack is a portion of RAM used for saving the content of Program Counter and general purpose registers.
Can ROM be used as stack? - ROM cannot be used as stack because it is not possible to write to ROM.
What is NV-RAM? - Nonvolatile Read Write Memory, also called Flash memory. It is also know as shadow RAM.
Wednesday, May 14, 2008
Microprocessor Interview Questions
Microprocessor x86 Interview Questions - 3
8086 Interview Questions 2008 Recent - 2
8085 Microprocessor Important Interview Questions 1
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