The document discusses the different addressing modes of the 8085 microprocessor. It defines addressing modes as the ways that an instruction's operands can be accessed. The 5 addressing modes of the 8085 are: 1) Immediate, where data is included in the instruction, 2) Register, where operands are in registers, 3) Direct, where the operand's address is in the instruction, 4) Register Indirect, where the operand's address is stored in a register pair, and 5) Implied, where the opcode specifies the operand without an explicit address. Examples are provided for each addressing mode.

1. Addressing Modes of
8085 Microprocessor
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Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

2. Addressing Modes of 8085
Microprocessor
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Er. Swapnil V. Kaware,
Assistant Professor
B.E. (Electronics), M.E. (Electronics)
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Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

3. Definition
• The addressing mode of a microprocessor
defines the way in which the operand of
instructions can be accessed.
• The various ways of specifying data (or
operands) for instructions are also called
as addressing modes.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

4. Opcode & Operand
• An opcode is short form for 'Operation Code.'
• Opcode is an instruction that tells processor what to do
with the variable or data written besides it.
• Oprand is a variable that stores data (and data can be a
memory address or any data that we want to process).
• e.g. MVI A,B
• here instruction MVI is an opcode. A & B are oprands.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

5. • Assembly language uses symbolic codes instead of
binary or to represent the opcodes known as
mnemonics.
• Mnemonics are instructions or commands to perform
a particular operation given by user to microprocessor.
• e.g MOV
MVI
ADD
SUB
Mnemonics
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

6. Types of Addressing Modes
1). Immediate addressing mode,
2). Register addressing mode,
3). Direct addressing mode,
4). Register Indirect addressing mode,
5). Implied/Implicit addressing mode.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

7. (1) Immediate Addressing Mode
• In 8085, the ‘I’ letter falls under this category.
• Letter ‘I’ Indicates “Immediate Addressing Mode”.
• The data can be either 8 bit or 16 bit.
• If the immediate data is 16 bit, the instruction is of 3 bytes.
• For Example:
• MVI A,20H: It moves 8 bit immediate data (20H) into
accumulator.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

8. (2) Register Addressing Mode
• In 8085, the “Register Addressing Mode “ specifies the
source operand, destination operand or both to be
contained in an 8085 register.
• This results in faster execution because it is not
necessary to access memory locations for operands.
• For Example:
• MOV A,B: It moves contents of register B into
accumulator (A).
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

9. (3) Direct Addressing Mode
• In 8085, the “Direct Addressing Mode” specifies the 16 bit
address of the operand within the instruction itself, the second
and third bytes of instruction contain 16 bit address.
• This is a 3-byte instruction.
• The address of the operand is available in the instruction itself
• For Example:
• STA 8000H; Store the contents of the Accumulator in the
location 8000H

10. (4) Register Indirect Addressing Mode
• In 8085, The 16-bit address location of the operand
stored in a register pair (H-L) is given in the instruction.
• The address of the operand is given in an indirect way
with the help of a register pair. So it is called Register
indirect addressing mode.
• For Example:
• MOV M,A: It stores the contents of Accumulator (A) into
Memory location (M), location pointed by HL register
pair.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

11. (5) Implied/Implicit Addressing Mode
• In 8085, the “Implied/Implicit Addressing Mode”,
opcode specifies the address of operands.
• This mode doesn't require any operand
• For Example:
• CMA : It Complements the contents of accumulator.
Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

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Microprocessor Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)