8085 instruction set description step by step with suitable examples

8085 instruction set with suitable examples

8085 micro processor is a 8-bit data bus, 8-bit control bus and 16-bit address bus along with 64k memory size.

—An instruction is a binary pattern designed inside a microprocessor to perform a specific function.

The entire group of instructions that a microprocessor supports is called Instruction Set.
8085 has 246 instructions.
Each instruction is represented by an 8-bit binary value.
These 8-bits of binary value is called Op-Code or Instruction Byte.
 

a 8085 micro processor supports 5 instruction set:

which are:

1. Data transfer instruction set

2. Arithmetic instruction set

3. Logical instruction set

4. Branching instruction set

5. Control instruction set 

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1. Data transfer instruction set:

 

These instructions move data between registers, or between memory and registers.
These instructions copy data from source to destination.
While copying, the contents of source are not modified.
 

2. Arithmetic instruction set :

These instructions perform the operations like:
Addition:

Any 8-bit number, or the contents of register, or the contents of memory location can be added to the contents of accumulator.
The result (sum) is stored in the accumulator.
No two other 8-bit registers can be added directly.
Example: The contents of register B cannot  be added directly to the contents of register C.

Subtract:

Any 8-bit number, or the contents of register, or the contents of memory location can be subtracted from the contents of accumulator.
The result is stored in the accumulator.
Subtraction is performed in 2’s complement form.
If the result is negative, it is stored in 2’s complement form.
No two other 8-bit registers can be subtracted directly.

Increment/Decrement:

 The 8-bit contents of a register or a memory location can be incremented or decremented by 1.
The 16-bit contents of a register pair can be incremented or decremented by 1.
Increment or decrement can be performed on any register or a memory location.

3. Logical instruction set:

These instructions perform logical operations on data stored in registers, memory and status flags.

The logical operations are:
AND
OR
XOR
Rotate
Compare
Complement
 

Any 8-bit data, or the contents of register, or memory location can logically have
AND operation
OR operation
XOR operation
    with the contents of accumulator.
The result is stored in accumulator.
 

 4. Branching instruction set

The branching instruction alter the normal sequential flow.

These instructions alter either unconditionally or conditionally.
 

 5. Control instruction set 

The control instructions control the operation of microprocessor.

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