Bus contention

Bus contention, in computer design, is an undesirable state of the bus in which more than one device on the bus attempts to place values on the bus at the same time. Most bus architectures require their devices follow an arbitration protocol carefully designed to make the likelihood of contention negligible. 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. Contention may also arise on systems which have a programmable memory mapping and when illegal values are written to the registers controlling the mapping.