LM3000 Clock

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The clock has two phases, which we call the Red phase and the Green phase.

[edit] Red Phase

Read

  • The instruction register is loaded from instruction RAM, which is fed into the instruction decoder.
  • The instruction decoder immediately goes to work instructing one of the microprocessor components to put its value onto the data bus. This could be an immediate value from the operand RAM, a value from a register, or the result from the ALU.

[edit] Green Phase

Write

  • The instruction decoder instructs one (or more) of the microprocessor components to write from the data bus. This could be a register, an ALU register, the status register (if we're checking for Z), and the program counter if a branch is taken.
  • If a branch is not taken, the program counter increments.
  • In either case, the updated address is fed to the instruction RAM in anticipation of the next Red phase.

Image:LM3000_Timing.gif

Timing Illustration (Illustrator file): Image:LMTiming.ai

Clock

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