Method of and device for bringing a network interface out of a s

Details Method of and device for bringing a network interface out of a s Method of and device for bringing a network interface out of a s

1990-08-31

1993-06-01

Atkinson, Charles E.

Excavating

361 88, 371 82, G06F 1100

Patent

active

052166740

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a network interface of a computer network having at least two bus lines and a plurality of substations interconnected by the bus lines. In particular, the present invention relates to a method of and a device for activating such a network interface out of a sleep mode into a wake-up mode even in the case of a failure of one bus line.
Computer controlled networks are being used more and more frequently, in particular also in motor vehicle construction. In particular, so-called controller area network interfaces for motor vehicles are known, which connect via the bus lines a multiplicity of components, subsystems and/or systems forming the respective substations of the network. The information items or bits of the network run via the two bus or signal lines. Any failure of one of the two signal lines due to short-circuiting to ground or to the voltage supply or an interruption of the lines has the consequence that communication among substations of the entire network breaks down. This is also the case if a short-circuit occurs between the two bus lines.
In my German Patent Application P 38 26 774, corresponding to U.S. patent application Ser. No. 466,283, filed Mar. 19, 1990 and assigned to the same assignee, it has been proposed for the detection and elimination of a global fault on the signal lines of the multiplex bus to provide the network interface with a fault detection device including a counter, with the aid of which an absence of information on the signal lines can be detected. However, the detection is possible only in the wake-up mode of operation of the interface.


SUMMARY OF THE INVENTION

The network interface in combination with the activation device according to the invention, in comparison with prior art interfaces of this kind, has the advantage that interface operation can be maintained even in the event of failure of one of the signal or bus lines of a network due to interruption or short-circuiting. In particular, it is possible to activate a network interface which is in sleep mode, i.e. to bring it into wake-up mode.
An exemplary embodiment of an activation device which has at least two comparators, the first input of which is coupled to one of the bus lines and the second input of which is coupled to a reference voltage, is particularly preferred. The outputs of the two comparators are connected to an evaluation circuit. Such an activation device of a network interface is of a very simple design. Slowly operating components, which are consequently very inexpensive, can be used as comparators. A network interface of such design is also distinguished by a very low closed-circuit current.
Also preferred is an exemplary embodiment in which the evaluation circuit is designed as an OR gate, the output of which emits a wake-up signal when an edge change occurs on an intact bus line. This wake-up signal has the effect of bringing the network interface out of sleep mode into the wake-up state, i.e. activating the interface. This exemplary embodiment can also be realised very inexpensively.
The network interface in combination with the activation device according to the invention has in comparison with the prior art the advantage that interface operation can also be maintained if there is a short-circuiting of the signal or bus lines of the network between each other. As a result, a very high operational reliability is ensured, even if faults occur in the network.
A preferred embodiment of this interface is distinguished by the fact that the activation device assigned to the bus lines and a reference voltage, which serves for the activation of the network interface in the event of a short-circuit of the buslines between each other and emits a wake-up signal, has at least two comparators, the first input of which is assigned to one of the bus lines and the second input of which is assigned to a reference voltage. In this case, a voltage offset between the two inputs of the comparators is produced by a voltage divider. The outputs of the comp

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