One-hot Scheme

• Requires less amount of combinational logic to decode states

• better time margin

• Good for eco

• Good for FPGA and ASIC

Encoded Scheme

• Requires less # of flops

• Better for ASIC
  • not restricted by flops

  

  Questions and Answers

  What’s the difference between a one-hot state machine and a binary-reduced state machine?

  • Binary reduced is basically simplified version of one hot state machine

  

  • Which would generally be faster (in terms of performance/maximum clock speed)?
    • One Hot
  • Which would generally be easier to create by hand?
    • One Hot (see https://edstem.org/us/courses/8915/discussion/645529)
      • In the one-hot example, the logic checking the state can simply use the one-hot bits for the multiplexing.
      • For the binary-encoded state, the logic has to include a load of decoder logic to convert the binary value to a one-hot value before it can do the multiplexing.
  • Which would generally require fewer logic gates to implement?
    • Binary encoded since it’s simplified

  Practice converting state diagrams to truth tables and vice versa

  • Review both of the problems on Homework 3

  Practice reading state machine circuits and translating them to state diagrams

  • For example: given the circuit of your one-hot state machine in Homework 3, translate it back into the state diagram without looking at the original
  • While you won’t need to actually build state machine circuits like in Homework 3, you should still be comfortable with the concepts from Homework 3.