RTL Design #39 · 2026-11-01 · Run detection · Easy · about 10 min

A run detector that pulses on every bit after the third

run_det pulses hit once for every three 1s in a row on a bit stream.

• A bit is transferred in each cycle where en is 1. din means nothing while en is 0, and cycles with en = 0 do not interrupt a run.
• A transferred 0 ends the run. Runs are counted in groups of three, not overlapping: after a group of three, the next 1 starts a new count. Seven 1s in a row give two pulses, after the 3rd and the 6th.
• hit is registered: it is 1 for one cycle, the cycle after the transfer that completed the group.
• rst_n is a synchronous, active-low reset that forgets any run in progress.

When you press Run, hit fires too often. Fix run_det.sv. Grading uses four hidden checks.

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