Instructions sets in 8085 microprocessor

Before go for Instructions sets in 8085 microprocessor, we should know 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. Now come to an instruction set is a collection of instructions that the microprocessor is designed to perform.

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.

An instruction comprises in 8085 microprocessor of 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 be 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

Now 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 be possible different way. The different types of data transfer operations possible are cited below:

  • Between two registers.
  • Between a register and a memory location.
  • A data byte can be transferred between a register and a memory location.
  • Between an I/O device and the accumulator.
  • Between a register pair and the stack.

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:

As name suggest that instructions in this group are 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 is used to do the logical operation. The logical operations include AND, OR, EXOR, compare, complement.

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:

This instructions are used to control the operation of 8085 microprocessor. The machine control operations are Halt, Interrupt and NOP (no operation).

Example: HLT; NOP.

Hope this above discussion on instructions sets in 8085 microprocessor is helped you.


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