Troubleshooting digital circuits: What common cause best explains erratic or seemingly unexplained activity on logic lines in an otherwise functioning system?

Introduction / Context:
Digital systems sometimes exhibit unexpected toggles or invalid states that appear sporadically. Understanding the most typical root cause helps technicians prioritize their measurements and fixes, whether using a logic analyzer, oscilloscope, or a simple logic probe.

Given Data / Assumptions:

• The system is clocked and intended to be synchronous.
• Intermittent, short-duration anomalies are observed.
• No deliberate asynchronous interface has been designed to tolerate hazards.
• Power rails and grounds are assumed adequate until proven otherwise.

Concept / Approach:
A glitch is a brief unintended pulse or hazard on a digital line, often originating from unequal path delays in combinational logic, improper synchronization of asynchronous inputs, or insufficient debouncing. Glitches can momentarily drive logic to incorrect levels, triggering downstream latches or counters unexpectedly. Recognizing a glitch as the likely culprit prompts targeted checks: hazard analysis, input synchronization, and layout or termination review.

Step-by-Step Solution:

Verification / Alternative check:
Trigger the oscilloscope on narrow pulse width or use logic analyzer glitch-capture features. If the anomaly coincides with logic reconvergence or asynchronous inputs, the diagnosis is reinforced.

Why Other Options Are Wrong:

Common Pitfalls:
Blaming the clock first; overlooking asynchronous inputs and debouncing; ignoring termination or ground bounce in fast edge-rate environments.

Final Answer:
a glitch