Shared digital buses – naming the error condition The condition that occurs when two or more devices attempt to drive (write to) a common bus at the same time is called:

Introduction / Context:
In digital systems, multiple ICs often share a common data bus. Proper arbitration and output-enable control are required to avoid electrical conflict. Recognizing the correct term for this fault is important in debugging.

Given Data / Assumptions:

• At least two devices can drive the bus.
• They are enabled simultaneously without tri-state isolation.
• The bus lines are common conductors with finite impedance.

Concept / Approach:
When two outputs drive different logic levels onto the same line, a short-like condition forms between supply rails through the drivers. This is known as bus contention and can cause excess current, signal corruption, and potential device damage.

Step-by-Step Solution:
Identify simultaneous drive: two output drivers active on one line.Recognize conflicting levels: one attempts HIGH, other LOW.Name the fault: bus contention.

Verification / Alternative check:
Oscilloscope traces often show rounded or mid-level voltages and overheating ICs during contention. System design uses tri-state, open-drain with pull-ups, or bus arbiters to prevent it.

Why Other Options Are Wrong:
Address decoding / multiplexing are design techniques, not fault conditions.“Bus collisions” is not the standard term; industry uses “bus contention.”

Common Pitfalls:
Leaving multiple devices enabled; forgetting pull-ups with open-drain; mis-timed enables during handover.

Final Answer:
bus contention