FA-88941 / Digital logic simulation / Open access

Transition exactly one setup time before the edge flagged · case 01

Data that changes exactly setup time units before the clock edge is reported as a setup violation.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The setup window is closed at its start, including the instant e - setup.

THE FAILURE

The setup window is closed at its start, including the instant e - setup.

Unsuccessful approach: Also closing the upper bound moves the edge instant from hold into setup without fixing the start boundary.

Case contract

Input [c0, clock, data, setup, hold]: c0 is the initial clock level, clock is time-sorted [t, v] transitions (possibly redundant), data is a list of data transition times. Rising edges are 0->1 changes only. For every data time t and every rising edge e: e-setup < t < e is a 'setup' violation, e <= t < e+hold is a 'hold' violation. Return all [e, t, kind] sorted by edge, then time.

Why this case matters

Timing checks in gate-level simulation decide which transitions corrupt a register; window boundaries and edge extraction are the classic bug sites.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(*args):
    c0, clock, data, s, h = args
    edges = []
    prev = c0
    for t, v in clock:
        if prev == 0 and v == 1:
            edges.append(t)
        prev = v
    out = []
    for t in data:
        for e in edges:
            if e - s <= t < e:
                out.append([e, t, 'setup'])
            elif e <= t < e + h:
                out.append([e, t, 'hold'])
    return sorted(out)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 18, 27], 3, 2], [[10, 8, 'setup'], [20, 18, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [21, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [13, 1]], [3, 5, 11], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 19, 27], 3, 2], [[10, 8, 'setup'], [20, 19, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 30], 3, 2], [[20, 20, 'hold'], [30, 30, 'hold']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 26], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [22, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [14, 1]], [3, 5, 12], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 5], 2, 2], [[4, 3, 'setup'], [4, 5, 'hold']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 17, 27], 3, 2], [[10, 8, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [23, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [15, 1]], [3, 5, 13], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 18, 27], 3, 2], [[10, 8, 'setup'], [20, 18, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 30], 3, 2], [[20, 20, 'hold'], [30, 30, 'hold']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 26], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [24, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [16, 1]], [3, 5, 14], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 5], 2, 2], [[4, 3, 'setup'], [4, 5, 'hold']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 19, 27], 3, 2], [[10, 8, 'setup'], [20, 19, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [25, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [17, 1]], [3, 5, 15], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
setup window boundaries	`[[10, 7, 'setup'], [10, 8, 'setup'], [20, 18, 'setup'], [30, 27, 'setup']]`	`[[10, 8, 'setup'], [20, 18, 'setup']]`	Failed
transition exactly at the clock edge	`[[20, 20, 'hold'], [30, 29, 'setup']]`	`[[20, 20, 'hold'], [30, 29, 'setup']]`	Passed
falling clock edges are not checked	`[]`	`[]`	Passed
redundant high transition is not an edge	`[]`	`[]`	Passed
clock already high at start	`[[13, 11, 'setup']]`	`[]`	Failed
clock low at start rises first	`[[4, 3, 'setup']]`	`[[4, 3, 'setup']]`	Passed
overlapping windows reported by edge	`[[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']]`	`[[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']]`	Passed

SHA-256 / e4be23ba5e16b2b6d6ae279168e35394f846914b1dc4d148e5f814e36393fbb9

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(*args):
    c0, clock, data, s, h = args
    edges = []
    prev = c0
    for t, v in clock:
        if prev == 0 and v == 1:
            edges.append(t)
        prev = v
    out = []
    for t in data:
        for e in edges:
            if e - s <= t <= e:
                out.append([e, t, 'setup'])
            elif e <= t < e + h:
                out.append([e, t, 'hold'])
    return sorted(out)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 18, 27], 3, 2], [[10, 8, 'setup'], [20, 18, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [21, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [13, 1]], [3, 5, 11], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 19, 27], 3, 2], [[10, 8, 'setup'], [20, 19, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 30], 3, 2], [[20, 20, 'hold'], [30, 30, 'hold']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 26], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [22, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [14, 1]], [3, 5, 12], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 5], 2, 2], [[4, 3, 'setup'], [4, 5, 'hold']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 17, 27], 3, 2], [[10, 8, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [23, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [15, 1]], [3, 5, 13], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 18, 27], 3, 2], [[10, 8, 'setup'], [20, 18, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 30], 3, 2], [[20, 20, 'hold'], [30, 30, 'hold']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 26], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [24, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [16, 1]], [3, 5, 14], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 5], 2, 2], [[4, 3, 'setup'], [4, 5, 'hold']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])], [('setup window boundaries', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [7, 8, 19, 27], 3, 2], [[10, 8, 'setup'], [20, 19, 'setup']]), ('transition exactly at the clock edge', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [20, 22, 29], 3, 2], [[20, 20, 'hold'], [30, 29, 'setup']]), ('falling clock edges are not checked', [0, [[10, 1], [15, 0], [20, 1], [25, 0], [30, 1]], [16, 25], 3, 2], []), ('redundant high transition is not an edge', [0, [[5, 1], [10, 1], [12, 0], [25, 1]], [9, 11], 3, 2], []), ('clock already high at start', [1, [[4, 1], [8, 0], [17, 1]], [3, 5, 15], 2, 2], []), ('clock low at start rises first', [0, [[4, 1], [8, 0], [12, 1]], [3, 6], 2, 2], [[4, 3, 'setup']]), ('overlapping windows reported by edge', [0, [[10, 1], [11, 0], [12, 1]], [11, 12], 3, 3], [[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
setup window boundaries	`[[10, 7, 'setup'], [10, 8, 'setup'], [20, 18, 'setup'], [30, 27, 'setup']]`	`[[10, 8, 'setup'], [20, 18, 'setup']]`	Failed
transition exactly at the clock edge	`[[20, 20, 'setup'], [30, 29, 'setup']]`	`[[20, 20, 'hold'], [30, 29, 'setup']]`	Failed
falling clock edges are not checked	`[]`	`[]`	Passed
redundant high transition is not an edge	`[]`	`[]`	Passed
clock already high at start	`[[13, 11, 'setup']]`	`[]`	Failed
clock low at start rises first	`[[4, 3, 'setup']]`	`[[4, 3, 'setup']]`	Passed
overlapping windows reported by edge	`[[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'setup']]`	`[[10, 11, 'hold'], [10, 12, 'hold'], [12, 11, 'setup'], [12, 12, 'hold']]`	Failed

SHA-256 / df3b5dd6c9ed2137b07d21b6347ae25c8b9cee3f757ec2a81c0836e9643324a5

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

A deterministic bounded teaching model of one simulator rule set; the contract is stipulated and is not a claim of conformance to any HDL standard or commercial simulator. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:12.984258+00:00.

Case digest / fef010c68d0915db4c302f4070974db27c6860e59b7a1a7e1ce468b4e04e4733