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Codiode/Problems/Sequential Logic

Period Measurement

MediumLogic CircuitBuild

Tachometers, frequency counters, and clock recovery circuits rely on precise timing measurements of incoming waveforms. Measuring the period of an unknown signal requires counting reference clock cycles between consecutive rising edges.

The circuit tracks the number of system clock cycles between rising edges of sig_in. An internal 8-bit counter increments by one every clock cycle. When a synchronous rising edge is detected on sig_in, the circuit must output the current counter value on period, assert the valid signal for exactly one clock cycle, and synchronously reset the counter to zero to begin the next measurement. The period output must hold its most recent measurement until a new measurement is ready. When rst is high, the counter resets to zero, period becomes zero, and valid is deasserted.

Constraints

  • Use synchronous reset logic exclusively.
  • The period output must be exactly 8 bits wide.
  • The valid output must be 1 bit wide and assert for only one cycle per detected edge.
  • Do not reset the counter if sig_in remains high: only reset on the transition from low to high.

Topics

CountersState MachinesEdge Detection

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