State machine designer

The page follows the sequential circuit design procedure: state table, state diagram, state assignment, transition table, flip-flop input and output equations, then a check.

• Moore or Mealy. A Moore output depends only on the present state, so it is written once per state and shown inside the circle. A Mealy output also depends on the input, so it is written per transition as input/output.
• State table. For each present state and input value, pick the next state. Click an output to cycle it through 0, 1 and x. An x is a don't-care, and so is a next state of x.
• State assignment. Binary and Gray codes use ⌈log₂ n⌉ flip-flops, and any unused code becomes a don't-care. Custom lets you type each state's code and pick from ⌈log₂ n⌉ up to n flip-flops; its unused codes are don't-cares too. One-hot uses one flip-flop per state, and each next-state equation ORs the transitions into that state: Q_i times the input condition for each incoming edge.
• Excitation. Each row of the transition table turns a change from Q to Q+ into flip-flop inputs: D = Q+, T = Q ⊕ Q+, and for JK one of the two inputs is a don't-care on every row.
• Equations are exact minimum sums of products. Open in K-map shows the same function, with its don't-cares, on a Karnaugh map.
• Check. The simulation runs your input sequence through the equations and compares every step with the state table. A wrong equation shows up as a mismatch.
• Share. The address bar always holds a link to the machine on screen, with its settings and input sequence. Copy link copies it.