Abstract: The communications adapter provides an interface between automotive vehicle on-board computer and a test computer running diagnostic software. Using a dual-ported random access memory, the circuit receives serial data from the on-board computer, preprocesses that data into a standardized data format, and places the standardized data directly into the memory space of the test computer. The dual-ported memory may be placed at a user selected address within the memory space of the test computer, so that it will not conflict with the diagnostic program running on the test computer. The invention is readily upgradable by uploading preprocessor software into random access memory, thereby making the invention upwardly compatible as new makes and models are introduced.

Abstract: A vehicular diagnostic system is described which generally comprises a portable communications control station and a remote data processing station. The control station includes a portable communications controller which is adapted to be connected to a vehicle data terminal capable of supplying parameter data monitored by a vehicle computer and connected to a source of electrical power in the vehicle. The controller also includes the circuitry required to enable the flow of the parameter data through the vehicle data terminal, to compose the data into a predetermined data stream, to record this data stream on magnetic tape, and transmit live or recorded data through a telephone line to the remote data processing station.

Abstract: Apparatus for maintaining a real time clock normally incremented by a CPU when power is provided thereto and maintained by a separate counting means when power is removed from the CPU, the separate counting means powered independently of the CPU power source. Apparatus is also disclosed for synchronizing the separate counting means such that the real time clock maintained by the CPU may be updated for the time interval in which the CPU was inoperative without loss of real time clock accuracy.