Question

1. Which Interrupt Has The Highest Priority?

2. Name 5 Different Addressing Modes?

3. How Many Interrupts Are There In 8085?

4. In 8085 Which Is Called As High Order / Low Order Register?

5. What Are Input & Output Devices?

Answer 1

1)

In the CPU, which disturbs the normal flow of execution is called interrupt.

Hardware Interrupts are triggered by pins present in the CPU.

TRAP is the interrupt which has highest priority.

Whenever this trap pin triggers, CPU interrupted and respective interrupt service routine will be executed.

It protects the memory in case of any failure. It is always be enabled.

2)

Addressing modes: It is the way the operand addresses are represented in the instruction format.

These are used to represent the effective address of physical memory location of the operands.

Example:

Immediate addressing mode:

In this operand is directly present in the instruction itself.

Format:

ADD

7

7 is operand

ADD is opcode

Example:

direct addressing mode:

In this operand’s physical memory address is present in the operand field of instruction.

Format:

ADD

#456

Assuming,#456 is memory address where operand 7 is present.

ADD is opcode

Register addressing mode:

If operands are present in the registers then address of register is mentioned in the operand field of instruction.

indirect addressing mode:

it is used to implement pointers. Operand field contains address of address of operand.

Index addressing mode:

If operand is present in the array, Operand field contains index number of operand.

It is used for array implementation.

3)

Total 5 interrupts are exist in 8085. Those are

TRAP

RST 7.5

RST 6.5

RST 5.5

INTR.

4)

High order register is Accumulator register.

It is directly connected to ALU. In one address instruction formats, this is helpful.

ALU first communicates with Accumulator register during any operation.

Low order register is flag register.

These are used to give status of operation performed by ALU.

Suppose, if subtraction operation is performed if result is zeo then zero flag will be enabled or else it won’t. So on seeing zero flag, ALU could know about status of result.

5)

Input devices are which gives input to the computer to perform operation.

Example:

Mouse gives coordinates as input.

Keyboard gives ASCII codes of characters and letters etc.

Scanner

Etc.

Output devices:

Which gives output from computer to give results after performing some operation are output devices.

Example:

Printer gives printed documents

Monitor gives display

Speakers

Etc.