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Instructions sets in 8085 microprocessor

So want to become a programmer need to know the instruction sets in 8085 microprocessor. But before go for Instructions sets in 8085 microprocessor, we should know what is an instruction?

What is an instruction?

An instruction is a command given to the microcomputer or microprocessor to perform a specific task or function on a given data. If we know instruction then we can define an instruction set. It is a collection of instructions that the microprocessor is designed to perform.

Classification of Instruction

Instructions sets in 8085 microprocessor can be classified into five groups. Those are

  • Data transfer (copy) group
  • Arithmetic group
  • Logical group
  • Branch group
  • Machine control group.

If we looks on an instruction of 8085 microprocessor then we found two parts of it.  It has an operation code which is called ‘opcode’ and the address of the data which is called ‘operand’, on which the opcode operates. So this is the basic structure of instructions of 8085 microprocessor on which an instruction is based. The opcode specifies the nature of the task to performed by an instruction. Symbolically, an instruction looks like

Instructions sets in 8085 microprocessor

Depending upon the word size of instruction in 8085 microprocessor we can categorize those in a three groups. Those are

  • 1-byte instruction : ADD B
  • 2-byte instruction : MVIC, 07
  • 3-byte instruction : LDA 4400

Finally go for some brief of Instructions sets in 8085 microprocessor.         

Data transfer (copy) group:

As name suggest instructions in this group are used to copy data form one place to another. Data transfer can possible by different way. The different types of possible data transfer operations shown below:

  • Firstly, between two registers.
  • Secondly, between a register and a memory location.
  • Thirdly, a data byte can be transferred between a register and a memory location.
  • Fourthly, between an I/O device and the accumulator.
  • And finally, between a register pair and the stack.

However it is very important to clear your concept that the term ‘data transfer’ is a misnomer—actually data is not transferred, but copied from source to destination.

Examples: MOV A,B

                   MVI A, 05

                   LXI H,C050

Arithmetic group:

Similarly in this group, as name suggest that instructions used for arithmetic operation. The arithmetic operations possible are addition, subtraction, increment and decrement.

Example: ADD B; SUB C; INR C; DCR C.

Logical group:

Instructions in this group used to do the logical operation. So the logical operations include AND, OR, EXOR, compare, complement can performed in this group.

Example: ANI 05; CMP B.

Branch group:

In 8085 microprocessor branch operations are Jump, Call, Return and Restart instructions.

Example: JMP C050; CALL D050; RET.

Machine control group:

Finally we come to last category that is machine control group. This instructions can used to control the operation of 8085 microprocessor. So the machine control operations are Halt, Interrupt and NOP (no operation).

Example: HLT; NOP.

Let’s check how you learn “Instructions sets in 8085 microprocessor” with a simple quiz.

8085 Architecture

Architecture of 8085 microprocessor

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Subham

Subham

Hi myself Subham Dutta, having 15+ years experience in filed of Engineering. I love to teach and try to build foundation of students. Try to make them imagine what they learn.

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