Digital Electronics - Memory and Storage - Discussion

Bus contention occurs when two outputs drive the same signal at the same time, This reduces the reliability of the chip because it has multiple drivers fighting each other to drive a common output. If bus contention occurs regularly, even for short times, the possibility of damage to the drivers increases.

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.

One place where this can occur, and that is often ignored, is during the turnaround of a bus. In a synchronous bus, when one device is driving the bus during one clock cycle and a different device is driving during the next clock cycle, there is a short time when both devices may be driving the bus.

Sir, please explain in detail.

Bus Contention

Bus contention is an undesirable state of the bus of a computer, in which more than one memory mapped device or the CPU is attempting to place output values onto the bus at once. Normally, integrated circuits that connect to the bus are designed so that the likelihood of bus contention is nil provided that the chips are operated within their rated set-up times and so forth. However, if the bus is deliberately driven too fast, these setup times may be violated -- leading to contention. Contention may also arise on a system whose memory mapping is programmable, and illegal values are written to the registers controlling the mapping.