Bus contention is an undesirable state in computer design where more than one device on a bus attempts to place values on it at the same time.
[1][failed verification] Bus contention can lead to erroneous operation, excess power consumption, and, in unusual cases, permanent damage to the hardware—such as burning out a MOSFET.
[2] Most bus architectures requires devices sharing a bus to follow an arbitration protocol carefully designed to make the likelihood of contention negligible.
[3] However, when devices on the bus have logic errors, manufacturing defects, or are driven beyond their design speeds, arbitration may break down and contention may result.
CAN bus, ALOHAnet, Ethernet, etc., all experience occasional bus contention in normal operation, but use some protocol (such as Multiple Access with Collision Avoidance, carrier-sense multiple access with collision detection, or automatic repeat request) to minimize the times that contention occurs, and to re-send data that was corrupted in a packet collision.