FA-88975 / Digital logic simulation / Member archive
Setup time ignored at timing endpoints · case 05
Every endpoint slack is too large by exactly the setup time.
Case contract
Input [pis, gates, outs, period, setup]: pis maps input -> arrival time; gates are [name, delay, fanins] in topological order. arrival(g) = delay + max fanin arrival. required(g) = min over fanout gates m of (required(m) - delay(m)), plus period - setup if g is an output. Slack = required - arrival over gates. Return [worst slack, critical path, sorted [gate, slack]] where the path ends at the output with least slack (ties by name) and walks back through the fanin with the latest arrival (ties by smallest name) to a primary input.
Why this case matters
Static timing engines back-propagate required times through fanout trees; min/max confusion and delay attribution errors change the reported critical path.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| diamond with shared fanout | [1, ["b", "g1", "g4"], [["g1", 1], ["g2", 3], ["g3", 3], ["g4", 1]]] | [0, ["b", "g1", "g4"], [["g1", 0], ["g2", 2], ["g3", 2], ["g4", 0]]] | Failed |
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