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  • MICROPROCESSOR

    Prepared by R.Kavitha Page 1

    QUESTION BANK

    Unit 1

    1. Explain the term Microprocessor. ( CO1-K2)

    A microprocessor is a multipurpose, programmable logic device that receives binary

    instructions from a storage device called memory accepts binary data as input and processes data

    according to those instructions and provides result as output.

    2. Classify the BUS. ( CO1-K2)

    Bus: Group of wires carrying information.

    Address bus: An address bus is a computer bus that is used to specify a physical address.

    Data bus: It provides transportation for data.

    Control bus: It carries signals that report the status of various devices.

    3. Compare CMP and SUB instruction of 8086.( CO1-K2)

    After execution of an instruction, CMP – It affects the flag SUB- It doesn’t affect the flag

    4. What is an Assembler Directive? (CO1-K1)

    Assembler directives help the assembler to correctly understand the assembly language

    programs to prepare the codes. There are some instructions in the assembly language program

    which are not part of processor instruction set. These instructions are instructions to the

    assembler, linker and loader. These are called as Pseudo – operations or as Assembler directives.

    5. Outline about operand and opcode. ( CO1-K2)

    Operand – It specifies the type of operation to be performed.

    Op code – data needs for completing the task

    6. Compare Maskable and Nonmaskable interrupts.(CO1-K2)

    The interrupts whose request can be either accepted or rejected by the processor are

    called maskable interrupts. The interrupts whose request has to be definitely accepted (or

    cannot be rejected) by the processor are called non-maskable interrupts.

    7. What is Procedure?(CO1-K1)

    The procedure is a group of instructions stored as a separate program in the memory and

    it is called from the main program whenever required. The type of procedure depends on where

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    the procedure is stored in the memory. If it is in the same code segment where the main program

    is stored then it is called “near procedure” otherwise it is referred to as far procedure.

    8. What is Recursive procedure? (CO1-K1)

    Recursive procedure is a procedure which calls itself. If the procedure is called 4 times,

    then it is decremented by one after each procedure CALL and the procedure is called again and

    again until it reaches zero.

    9. Tell the different ways of interrupting processor. (CO1-K1)

    The processor can be interrupted in the following ways:

    i) by an external signal generated by a peripheral,

    ii) by an internal signal generated b y a special instruction in the program,

    iii) by an internal signal generated due to an exceptional condition which occurs while executing

    an instruction. (For example, in 8086 processor, divide by zero is an exceptional condition which

    initiates type 0 interrupt and such an interrupt is also called execution).

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    10. Draw the diagram for pipeline operation.(CO1-K1)

    UNIT 2

    1. Explain the term Multiprocessor. ( CO2-K2)

    Multiprocessor Systems refer to the use of multiple processors that execute instructions

    Simultaneously and communicate.

    2. Classify the bus arbitration mechanism. (CO2- K2)

    Bus Arbitration:

    The mechanism which decided the selection of current master to access bus is known as

    Bus arbitration. Three mechanisms are normally used:

    1. Daisy chaining.

    2. Polling.

    3. Independent requesting

    3. Show the interaction between 8086 and 8087 in diagrammatic format.( CO2-K2)

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    4. Outline about single step Interrupt. (CO2-K2)

    • As in 8086, this is an internal interrupt that comes into action, if trap flag (TF) of 80286

    is set.

    • The CPU stops the execution after each instruction cycle. So, that the register contents

    (including flag register), the program status word and memory, etc. may be examined at

    the end of each instruction execution. This interrupt is useful for troubleshooting the

    software. An interrupt vector type 01 is reserved for this interrupt.

    5. Summarize the functions of the following signals in 80286. PEREG, PEACK. (CO2-K2)

    • PEREG and PEACK (Processor Extension Request and Acknowledgement) Processor

    extension refers to coprocessor. This pair of pins extends the memory management and

    protection capabilities of 80286 to the processor extension 80287. The PEREQ input

    requests the 80286 to perform a data operand transfer for a processor extension. The

    PEACK active-low output indicates to the processor extension that the requested

    operand is being transferred.

    6. Summarize the functions of the following signals in 80286. HOLD and HLDA. (CO2-K2)

    • HOLD and HLDA: This pair of pins is used by external bus masters to request for the

    control of the system bus (HOLD) and to check whether the main processor has

    granted the control (HLDA) or not, in the same way as it was in 8086.

    7. Outline about single step Interrupt. (CO2-K2)

    • As in 8086, this is an internal interrupt that comes into action, if trap flag (TF) of 80286

    is set.

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    • The CPU stops the execution after each instruction cycle. So, that the register contents

    (including flag register), the program status word and memory, etc. may be examined at

    the end of each instruction execution. This interrupt is useful for troubleshooting the

    software. An interrupt vector type 01 is reserved for this interrupt.

    8. Short notes on Transcendental Instructions of 8087. (CO2-K2)

    FPTAN - Compute the values for a ration of Y/X for an angle in ST. The angle must be

    expressed in radians.

    F2XM1 – Compute the function Y=2x – 1 for an X value in ST. Result will be stored in ST by

    replacing X value.

    9. What is the importance of IOPL signal in 80286? (CO2-K2)

    IOPL – Input Output Privilege Level flags (bit D12 and D13)

    IOPL is used in protected mode operation to select the privilege level for I/O devices.

    10. What is the necessity of Memory Management unit?( CO2-K2)

    The part of main memory in which the operating system and other system programs are

    stored is not accessible to the users.

    In view of this, an appropriate management of the memory system is required to ensure the

    smooth execution of the running process and also to ensure their protection. The memory

    management which is an important task of the operating system is supported by a hardware unit

    called memory management unit.

    Unit 3

    1. What is the purpose of 8255? (CO3-K1)

    The 8255 is a widely used, programmable parallel I/O device. It can be programmed to

    transfer data under various conditions. It is flexible, versatile and economical (when multiple I/O

    ports are required). It is an important general purpose I/O device that can be used with almost

    any microprocessor.

    2. What is the purpose of 8251? (CO3-K1)

    8251 is a Universal Synchronous and Asynchronous Receiver and Transmitter

    compatible with Intel‘s processors. This chip converts the parallel data into a serial stream of bits

    suitable for serial transmission. It is also able to receive a serial stream of bits and convert it into

    parallel data bytes to be read by a microprocessor.

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    3. Compare Linear and Absolute decoding. (CO3-K2)

    In the absolute decoding technique the memory chip is selected only for the specified

    logic level on the address lines: no other logic levels can select the chip. This address technique

    is normally used in large memory systems.

    In small system hardware for the decoding logic can be eliminated by using only required

    number of addressing lines (not all). Other lines are simply ignored. This technique reduces the

    cost of decoding circuit, but it has drawback of multiple addresses.

    4. Summarize input and output port. (CO3-K2)

    Input port: It is used to get the data from the input device such as keyboard and send it to the