Shared bus behavior: When two or more devices attempt to drive their own digital levels onto a shared data bus at the same time (without proper arbitration or tri-state control), bus contention occurs. Assess the accuracy of this statement.

Introduction / Context:
Digital systems often use a shared bus to connect multiple ICs. To prevent damage and logic errors, only one device should actively drive the bus at a time unless the bus uses a wired-OR/wired-AND topology with passive pull elements. The term “bus contention” describes the fault condition when multiple active drivers assert conflicting levels.

Given Data / Assumptions:

• Multiple potential bus masters or slaves share lines.
• No tri-state, open-drain, or arbitration mechanism is engaged, or it is misused.
• Drivers can source and sink current strongly.

Concept / Approach:
On a push-pull (totem-pole) bus, two drivers fighting—one driving HIGH and another driving LOW—create excessive current, possible damage, and undefined logic levels. Proper design uses tri-state outputs with enable signals, open-drain/open-collector interfaces with pull-up resistors, bus transceivers, and arbitration protocols (e.g., grants, chip selects) to ensure only one active driver at a time.

Step-by-Step Solution:
1) Identify the bus topology (push-pull vs open-drain).2) Ensure outputs are tri-stated when not selected (via OE or direction control).3) Use chip-select and arbitration so exactly one device drives at a time.4) If multiple devices drive simultaneously, contention results—confirming the statement.

Verification / Alternative check:
Bus standards (e.g., PCI, parallel memory buses, microcontroller GPIO buses) specify tri-state timing to avoid overlap; I2C avoids contention by open-drain wiring and level-dominance rules.

Why Other Options Are Wrong:
“Incorrect” ignores basic electrical behavior. Restricting to open-collector or both-HIGH cases misses that contention is specifically problematic when drivers oppose levels; open-drain buses are designed to avoid destructive contention.

Common Pitfalls:
Enabling two tri-state drivers at once; misunderstanding turnaround timing; forgetting bus-holder components can mask but not fix contention.

Final Answer:
Correct