METHOD AND APPARATUS FOR SIGNALING ON-LINE FAILURE DETECTION

摘要

Method and apparatus permitting a multi-module digital system, such as a computer, having built-in test hardware associated with each module, including a plurality of signal processing units to communicate over two wire circuitry not only the existence of a failure of a particular module, but also its causality. This is accomplished by means of a four state signaling circuit interposed between each signal processing unit of a particular module and a module built-in test circuit which operates once an error output is reported by a signal processing unit to provide a further four state indication of the details of the failure.