The present invention relates to a communication control unit for controlling communication between an electronic control unit and other equipment.
Substantial advances have been made in recent years in the field of electronic control executed by microprocessors and the like, and highly accurate control of various types of equipment has been attained. In this respect, communication between an electronic control unit which utilizes such a microprocessor and other equipment (e.g. one or more other electronic control units) is extremely important. For example in the case of recently produced types of motor vehicles, control of various units of equipment installed in the vehicle is executed by means of electronic control units. A plurality of such electronic control units can be mutually coupled by a data link so that data which is supplied to one electronic control unit from a source such as a sensor can also be supplied to other electronic control units or equipment.
Such communication between an electronic control unit and other units of equipment, or between on electronic control unit and another, is generally carried out by using communication control units. One communication control unit may be formed integrally with each electronic control unit, or a communication control unit may be coupled to an electronic control unit to be controlled thereby. This has the advantage of ease of implementing the communication function, while in addition, if the communication control unit is formed integrally with the electronic control unit, the additional advantage is obtained of increased general applicability. However, the following problems also arise.
Specifically, in the case in which a communication control unit is formed integrally with an electronic control unit, e.g., in which each electronic control unit incorporates a microprocessor and the functions of the communication control unit are implemented by the operation of the microprocessor, if a failure status occurs in the electronic control unit due to the effects of electrical noise or to occurrence of component failure, etc., then the effects of this failure status will be transferred from that electronic control unit to other equipment or other electronic control units. As a result, the trouble resulting from this failure condition may become widely disseminated to other equipment, in spite of the fact that a communication control unit is utilized in the electronic control unit which has failed.
When one or more of such electronic control units are used in a motor vehicle, then such a widespread dissemination of trouble resulting from failure of a single electronic control unit can have extremely serious consequences, since various major operating function of the vehicle will generally be controlled on the basis of data produced from the electronic control units. Thus, an improvement in this respect is necessary in order to attain increased safety of operation of such a motor vehicle.
It is an objective of the present invention to provide a communication control unit which will overcome the problem described above, whereby in the event that a failure condition occurs in an electronic control unit, protection is provided such that this failure status will have no effect upon other equipment or other electronic control units which are connected to the faulty electronic control unit.