LC3 Macrostate 3 Clock Cycles Gets the next instruction from Memory and puts it in the Instruction Register

Fetch 1 (MAR PC, ++PC)

  • GatePC = 1
  • LD.MAR = 1
  • PCMux = 00 (inc)
  • LD.PC = 1

Fetch 2 (MDR mem[MAR])

  • MEM.EN = 1
  • LD.MDR = 1

Fetch 3 (IR MDR)

  • GateMDR = 1
  • LD.IR = 1

See also

Datapath