Sunday, February 28, 2016

8051 Instruction Set Overview

8051 Instruction Set

  • 8051 instruction set is optimized for 8-bit control applications
  • 8051 instructions have 8-bit opcodes
  • 28 = 256 instructions
  • 255 instructions are implemented
  • 1 instruction is undefined
  • 139 1-byte instructions
  • 92 2-byte instructions
  • 24 3-byte instructions
  • Instruction is made up of an operation code (op-code) followed by either zero, one or two bytes of operands
  • The op-code identifies the type of operation to be performed while the operands identify the source and destination of the data
  • Operand can be
  • - The data value itself
    - A CPU register
    - A memory location
    - An I/O port
  • If the instruction is associated with more than one operand, the format is always:
  • - Instruction Destination, Source
  • Where does the data for an instruction come from?
  • - Addressing Modes
  • Supports the following addressing modes
  • - Register, Direct, Indirect, Immediate, Relative, Absolute, Long, Indexed
  • Instructions are divided into five groups
  • - Arithmetic
    - Logical
    - Data Transfer
    - Boolean Variable
    - Program Branching



Related topics:
8051 Instruction Cycle   |   8051 Machine Cycle   |   8051 Instruction Set Summary   |   8051 Arithmetic Operation Instructions   |   8051 Logical Operation Instructions   |   8051 Data Transfer Instructions   |   8051 Boolean Variable Manipulation Instructions   |   8051 Program Branching Instructions   |   8051 Instruction Opcode   |   8051 Instructions that Affect Flag Settings   |   8051 Instructions and Examples

List of topics: 8051

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