Method and apparatus for inducing bus saturation during operational testing of busses using a pattern generator

Abstract

Bus testing logic is built into some of the devices connected to the bus to enable these devices to perform diagnostic testing of the bus. Under control of the test logic, the devices drive the bus with output voltages corresponding to a predetermined test bit pattern that is selected to cause the bus to reach a target bus utilization level. The bus signals produced by the devices propagate along the bus and are received by other devices. The received bus signals are resolved into a received bit pattern. The received bit pattern is compared with the test bit pattern used to generate the bus signals in order to detect discrepancies. In one embodiment, the devices can operate in a first mode by driving the bus in accordance with performing normal functions or in a second mode by performing diagnostic testing on the bus by driving the bus in accordance with the test bit pattern. Test patterns can be interleaved with normal bus signals. Alternatively, the test logic in the devices can arbitrate with the normal circuitry to assume control of the bus for testing purposes. In still another embodiment, a first device includes both a bus driver and a bus receiver and a second device includes logic for looping the bus signals back to the device that generated the signals.