Multiplex communications – Diagnostic testing – Fault detection
Reexamination Certificate
1999-03-01
2003-07-29
Yao, Kwang Bin (Department: 2662)
Multiplex communications
Diagnostic testing
Fault detection
C370S364000, C370S395310, C361S090000, C714S721000
Reexamination Certificate
active
06600723
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a method for testing and safeguarding the availability of a networked system. In particular, the method relates to safeguarding the availability of a networked system that is, inter alia, also connected with possible reference-earth potential displacements.
German patent document DE 42 12 742 A1 discloses a method for detecting errors in a data bus having two bus lines which are driven via output stages at least of one of the bus subscribers. Here, the possibility exists that the two output stages of a bus subscriber are driven simultaneously upon commissioning of the data bus. In this case, the ability to determine the level of the potential of a bus line and to generate an error report by the bus subscriber given a lack of agreement with a set point is provided.
U.S. Pat. No. 4,908,822 describes a multiplex system for addressing, controlling and monitoring the status of a multiplicity of electric devices which are distributed throughout a vehicle. A component of the multiplex system is two bus lines via which respectively identical messages are transmitted in series. In this case, the bus lines are each operated as single-wire buses which address a multiplicity of microcontrollers, each of the last of which respectively drives two control elements. Signals with a variable pulse duty factor can be impressed on the bus lines for test purposes, in order to thereby switch addressable control elements on and off. Switching means of the controllers provide current signals for representing the status of the element respectively driven.
Reference may be further made to German patent document DE 19611944 A1; WO97/36399; WO97/36398 and to patent application PCT/EP97/01534, which was submitted at the same time with the present application, the disclosures of which are expressly incorporated by reference herein.
In this case, German patent document DE 19611944 A1, describes an integrated semiconductor circuit with an electronic control unit having a microcontroller. Here, the control unit is able to communicate with other control units which are controlled by microcontrollers and for this purpose form a controller area network (CAN) in which communication is conducted on the basis of the protocol via a two-wire line. For this purpose each control unit has a bus protocol function.
According to the invention disclosed in DE 19611944A1, in the first embodiment, this circuit maximizes the availability of the CAN. This is accomplished because, on the one hand, it implements a transceive function which tolerates bus errors and also permits communication even in the presence of a bus error, and on the other hand it has means for detecting and treating bus errors, which in the case of an error isolates the bus from its normal subscriber terminations and reterminates it. As a result of this, while maintaining an ability to communicate, the circuit prevents (particularly in the case of very large CANs) parasitic currents from flowing away from subscribers via the bus into the bus error point in a bus-wide manner. The parasitic currents limit the availability of the network to the point of exhausting the battery in a battery-supported bus system. That circuit to this extent integrally increases the network availability on two levels, specifically on the level of communication and on the level of system energy. Another strategy, likewise for increasing the availability, is pursued by a different embodiment of that circuit.
WO97/36399 describes a method for determining potential displacements between electronic modules in a wire bus-type network, or the correspondence quality of their communication service levels in the network interconnection. Here, the bus medium comprises at least one wire which is connected electrically to the electronic modules. According to the invention disclosed in WO97/36399, an offset voltage is added in at least one bus subscriber (test subscriber) at the transmitting end to (at least) one (of the two) dominant, normal source level(s) and a test message is transmitted into the bus-type network by the test subscriber in this status. In this case, the source level is varied in a predetermined way. Depending on whether the (at least) one (of the two) dominant source level(s) is lowered or raised by the respectively adjustable offset voltage, the bus subscriber, which has a (reference-earth) potential error loses or gains its ability to receive. This condition is evaluated. Furthermore, WO97/36399 describes a device which comprises cooperative potential-controlling means hat are or can be connected to the transceiver function of a bus subscriber. Here, the device implements together with the controlling means, at least with respect to parts of the transmitting and/or receiving means of the transceiver function, at least one controllable voltage source which permits the exertion of an influence on at least one source level that is dominant during transmission and/or at least one signal level that is discriminant during reception.
WO97/36398 describes a semiconductor circuit for an electronic device which has at least one microcontroller. The circuit comprises at least one voltage regulator for providing, from a first supply voltage, at least one second supply voltage for the at least one microcontroller and for circuits of the device which cooperate with the microcontroller. Furthermore, as a monolith, this circuit comprises a transceiver function having transmitting and receiving means for coupling a microcontroller to a two-wire bus. According to a development of the invention disclosed in WO97/36398, this circuit further comprises watchdog functions, various wake-up functions and an interface via which serial data exchange is possible with the at least one microcontroller. Moreover, the circuit can have means for network-wide determination of bus subscribers with reference-earth potential errors and for quantifying such errors.
Various developments of these means in conjunction with special designs of the receiving part of the transceiver enable a bus-type network, for example of the CAN type, based on the circuit to make a latent determination (as the most important measure of the bus Q) of the margin of error still present in advance of the first occurrence of an operational failure caused by a level error.
PCT application PCT/EP97/01534 describes a method for testing the grounding of parts of a bus-networked system. In this case, steady-state potentials on bus lines are compared with reference-earth potentials which can be generated inside a bus subscriber. This comparison is used to infer (in each case) the quality of the interface between the bus subscriber under consideration and the earth reference conductor which is common throughout the network. A device for carrying out this method is also proposed herein.
Networked systems for control purposes which are based on a wire bus as means of communication are experiencing an increased importance. Examples are bus-type networks according to the J1850- or CAN-standard.
In such networked systems, a multiplicity of bus subscribers (these preferably being electronic controllers), of which each contains a microprocessor or a microcontroller, communicate with one another via a bus-type network. In the case of a CAN for example, the bus-type network comprises two conductor strands or wires which are normally keyed dominantly in phase opposition.
At the same time, there are also bus-type networks which use (as a bus medium) a single conductor strand or wire over an electric busbar or common surface. In these networks, though, the bus medium mostly serves as a power supply conductor. In this case, the subscribers communicate via the bus-type network via transmitting/receiving means (so-called bus transceivers). In each case, as an essential component of each bus subscriber, the so-called bus transceivers physically couple the latter to the bus-type network.
These transceivers for transmitting and receiving the data messages convert data messages from the logic leve
Minuth Juergen
Reeb Max
Setzer Juergen
Crowell & Moring LLP
Daimler-Chrysler AG
Nguyen Hanh
Yao Kwang Bin
LandOfFree
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