Little Computer 3

LC-3 minimal computer from introduction to computing systems

  • 16bit instructions
    • 4bit opcode
    • 12bit operands
  • Memory
    • 8 General Purpose Registers of 16bit
    • Address space: 16bit
    • Adressibility: 16bit
    • Load/store architecture: load data first in registers before performing operations.
  • ALU
    • Only has ADD, AND and NOT operations, other operations must by implemented by programs

Instruction processing #

  • Fetch
    • Load instruction into IR
    • Increase PC to next instruction
  • Decode: examinates opcode
  • Evaluate address: sign-extend addresses needed
  • Fetch operands: obtains source operands
  • Execute: executes the instruction performed in ALU
  • Store result: store result into memory