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B.E.,/B.TECH., ELECTRONICS AND

COMMUNICATION ENGINEERING REG 2008

UNIT AND 2

SUBJECT : EC 2304/Microprocessor And Microcontroller

TYPE : University Question paper 2marks with answer

1.

Define instruction cycle and machine cycle.

The total time required to complete the execution

of a single instruction is known as the instruction cycle.

It is defined as the time required to complete one

operation such as, op code fetch, memory read & write,

I/O read write, ack cycle.2.

Give the format of flag register in 8085.

7 6 5 4 3 2 1 0

S Z X AC X P X CY

S-sign flag, Z-zero flag, X-not use, AC-auxiliary carry flag,

P-parity flag, CY-carry flag.

3.Discuss the terms 2 key lockout, N-key Rollover.

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2 key lockout: In this mode, simultaneous key depression

is not allowed. When any key is depressed, the debounce

logic is set and 8279 checks for any other key depress

during next two scans.

N key rollover:Here, each key depressed independently

from all others.

4.

Give the control word format of 8255.

0 x x x D3 D2 D1 D0

0-bit reset, D0(1 for set, 2 for reset)

5.What is Try-state devices.

Try state devices those are can be exhibit a high

impedance state with 0 and 1. This can be help in bus

oriented devices where ports of many chips will have to be

used.6.

Mention the advantages of using the direct memory

access(DMA).

DMA allows a peripheral device to read from / write to

memory without going through the CPU. DMA allows for

faster processing since the processor can be working on

something else while the peripheral device can bepopulating memory.

7.What is purpose of following

(a)

AAD. (b) RCL.

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AAD: ASCII Adjust for division instruction adjusts the

unpacked BCD divided in AX be fore a division

operation.

RCL:Rotate through carry left ins rotates the contents

left through carry by the specified number of bits in

count operand.

8.

Write an 8086 assembly language program to multiply

two 16bit unsigned numbers to provide a 32 bit result.

Assume that the two numbers are stored in CX and DX .

CODE SEGMENT

ASSUME CS: Code

MOVE AX, DX

MULCX

HLT

CODE ENDS

END

9.

When the 8086 processor is in minimum mode and

maximum mode ?

The logical level at this pin decides whether the processor it to

operate either max or min.

If logic 1 mode is min. if logic 0 mode is max.

10.

Define segment override prefix.mov AX,[ES:60126] ; use ES as the segment

mov AX,[CS:bx] ; use CS as the segment

mov AX,[SS:bp+si+3] ;use SS as the segment

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11.

What are the 8086 instruction used for BCD

arithmetic?

DAADecimal adjust accumulator

DAS

Decimal adjust after subtraction

12. List any four programs control instruction available

in 8086.

JAJNBE- jump if above / jump if not below or not equal

JEJZ- Jump if equal / jump if zero flag

JO- jump If overflow flag=1

JS- jump if sign flag=1

13. What is Microprocessor .diff b/w CPU and p?

p is a multipurpose programmable device that reads binary

instruction from a storage device called memory, it accepts binary

data as i/p and process the data according to those instruction

and provides results as o/p.

CPU consists of ALU and control unit.

14.

Why the program counter and the stack pointer areregisters of 16bit?

Program counter is 16bit because it points to the 16bit memory

address. Stack pointer to a memory location in R/W memory

called the stack.

15.

What is an assembler Directives? Give two

Examples.

Assembler directives help the assembler to0 correctly understand

the assembly language programs to prepare codes.

Examples : DW,ASSUME,EQU,DB

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16.

List any two external hardware synchronization

instruction of 8086 p.

LOCK

WAIT

17. What is meant by minimum mode system configuration

in8086 microprocessor ?

The p 8086 is operated in minimum mode by connecting its

MN/MX pin to logic 1. The minimum mode system uses only one

processor.

Mention different data transfer schemes?

1.Parallel data transfer

a. Programmed I/O

b. Interrupt I/O

1.Serial data transfer

18. What is assembler ?

An assembler is a program used to convert an assembly language

program into the equivalent machine code modules which may

further be converted to executable code.

19. What is purpose of LEA instruction in 8086?

The load effective address instruction loads the offset of an

operand in the specified register.

Example: LEA BX, ADR

20.

How clock signal is generated in 8086 p?The 8086 does not have a internal clock circuit. The 8086 requires

an external asymmetric clock source with 331 duty cycle. The

8284 clock generator is used to generate the required clock for

8086.

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21. State the function of queue status QS0 and QS1 in 8086?

QS0 QS1 Indication

0 0 No operation

0 1 1

st

byte of opcodefrom queue

1 0 Empty queue

1 1 Subsequent byte

from queue.

22. How will carry and zero flags reflect the result of the

instruction CMP BX, CX ?

CMP BX, CX

Condition Zero flag Carry flag

CX>BX 0 0

CX=BX 1 0

CX