Switch bounce and erratic register outputs — diagnosing the cause A push-button switch is used to input data to a digital register, but the register's output appears erratic. What is the most likely cause of the problem?

Introduction / Context:
Mechanical push-buttons and toggle switches rarely make a single, clean transition. Instead, their contacts briefly chatter between open and closed states for a few milliseconds. When feeding an edge-sensitive digital input, this “bounce” can be interpreted as multiple presses, leading to unpredictable register contents or multiple counts in counters.

Given Data / Assumptions:

• Human-operated push-button connected to a register input (directly or via minimal conditioning).
• Observed symptom: erratic or non-reproducible register output.
• No evidence yet of power or IC failure.

Concept / Approach:
Contact bounce produces a burst of rapid transitions that digital logic may interpret as many presses. The standard remedy is debouncing, either with hardware (RC + Schmitt trigger, dedicated debounce IC) or with firmware filtering (if sampling via a microcontroller). Without debouncing, even a healthy power supply and ICs will exhibit erroneous behavior when driven by a raw mechanical contact.

Step-by-Step Solution:

Verification / Alternative check:
Scope the switch node during a press; you will see a burst of transitions over 1–10 ms instead of a single clean edge.

Why Other Options Are Wrong:

• Noisy power supply: would affect many nodes, not just the buttoned input.
• Corroded socket contacts: possible but typically produce static faults, not consistent per-press chattering.
• Intermittent IC: far less common; always eliminate bounce first.

Common Pitfalls:
Driving direct, non-Schmitt inputs from switches; neglecting pull-ups/downs that set a defined idle level.

Final Answer:
The switch contacts are bouncing.