Electrical computers and digital processing systems: multicomput – Computer-to-computer data routing
Reexamination Certificate
1999-03-04
2002-10-22
Wiley, David (Department: 2158)
Electrical computers and digital processing systems: multicomput
Computer-to-computer data routing
C709S244000
Reexamination Certificate
active
06470393
ABSTRACT:
TECHNICAL FIELD
The invention relates to an interface for a data node of a data network, a data node provided with such an interface, and a data network comprising such data nodes. The data nodes of such a data network communicate with each other via a bus line interconnecting them, with each data node being capable of constituting a transmitter or a receiver.
BACKGROUND OF THE INVENTION
Networks have been used for some time in motor vehicles, where they are known under the term CAN (Car Area Network). Such CAN systems comprise two open or ring-line-like shared lines, namely a bus line for data and message communication and a voltage supply line for supplying a battery voltage to the individual nodes.
The individual data nodes usually comprise a data processing unit, in particular in the form of a microcontroller, and a voltage supply unit, in particular in the form of a voltage controller, with both the microcontroller and the voltage controller being coupled via an interface to the bus line and the voltage supply line, respectively.
The voltage controller and in particular also the microcontroller consume both a relatively high current in the active state. In case of a data network having all of its data nodes in the active state, this had the effect of a correspondingly high consumption of electrical energy. This would lead to relatively fast discharging of the vehicle battery, when the vehicle is not used for a longer period of time. This problem conventionally is counteracted by switching the individual data nodes to a quiescent state when their activity is not required and by bringing them from this quiescent state to the active state only when their activity is required. For example, in case of a vehicle at standstill, in particular when it has an alarm system, the door contacts are cyclically examined. Usually the term “waking up” is employed for this activation of data nodes.
When, in conventional CAN systems, data are sent from a data node via the bus line, all data nodes are awakened completely. In doing so, the voltage controller is activated in each data node via its interface in order to tap the operating voltage from the voltage supply line and to bring the microcontroller to the active mode of operation by feeding supply voltage thereto.
A message sent from a data node via the bus line contains an address part and a data part. The address part contains the addresses of the data nodes to be addressed with the respective message transmitted. An address may be intended for one single data node exclusively or for a predetermined choice of data nodes.
The individual data nodes are equipped with address filters by means of which they can recognize whether or not the address of the message transmitted via the bus line is an address intended for them.
Such an address selection or address filtering can be carried out, for example, by means of circuit arrangements and methods as indicated in the applicant's own German patent applications 196 45 055.1 and 196 45 057.8. the contents of which are herewith incorporated by reference herein. In such address selection methods, either the entire address bit sequence as a whole or individual segments of predetermined length of the address bit sequence are compared to address words or address segments, respectively, which are stored in the respective data node. If one data node is to be capable of accepting various address codes, either a number of address filters corresponding to the number of addresses or address segments to be accepted is required or, in addition to the filters, masks are employed determining for the individual filter bit locations whether acceptance of an address bit location received is to take place for them only when the address bit of the corresponding address bit location is in conformity with the associated filter bit location, or whether acceptance is to take place irrespective of whether or not there is conformity of the respective address bit location considered with the associated filter bit location.
With conventional CAN systems, address filtering takes place in the microcontroller. When data are transmitted from a data node, full waking up of all data nodes takes place in order to enable the microcontroller of each data node by activation thereof to carry out address filtering and to thus determine whether or not the message on the bus line causing waking up is intended for the particular data node. Since the voltage controllers, and in particular the microcontrollers, consume relatively large amounts of electrical energy in the active state, even a mode of operation in which, when the vehicle is inoperative, the data nodes are brought to a quiescent state and are awakened to the active state only from time to time, mostly in cyclic manner, still results in relatively high consumption of energy and a correspondingly high load on the vehicle battery. When such a vehicle is parked for a longer period of time, for example in an airport car park during a longer air travel, the vehicle battery may be discharged as early as after periods of 1 to 2 weeks by such cyclic waking up or activation of all data nodes.
SUMMARY OF THE INVENTION
It is an advantage of the invention to provide a remedy in this respect and to make available, in particular for CAN systems, a method resulting in lower consumption of energy and thus a prolonged energy supplying capacity of the vehicle battery also in case of inoperative intervals of the vehicle of longer duration.
According to an embodiment of the invention, the interface of each data node is equipped with an activating address filter so that activating address filtering for an activating demand transmitted via the bus line can be carried out already in the interface. This eliminates the necessity of waking up the entire data node, in particular the microcontroller, for activating address filtering and switching the same to the energy-consuming active state.
The interfaces of the individual data nodes require considerably less electrical energy than the microcontroller. In addition thereto, the interfaces can be held in a low-power status when no data are transmitted via the bus line. When an activating demand is transmitted via the bus, the interfaces of all nodes, in this embodiment, are set into an active state rendering possible activating address filtering or activating address identification. In this status, all interfaces examine whether the address part of the message transmitted via the bus line contains an address intended for them.
Only when an interface recognizes an activating address intended for its data node does it effect activation of its data node, e.g., by activating a voltage controller belonging to this data node and thus waking up of the associated microcontroller to the active state thereof.
Waking up of the interfaces to their state in which they arc capable of performing activating address identification or filtering, is effected preferably by means of a characteristic frame start bit preluding the message frame of each message transmitted via the bus line.
Programming of the interface of a data node with respect to the address or addresses recognizable by the same can be effected by the associated microcontroller.
Due to the fact that the microcontrollers of conventional CAN systems have an address filter of their own, the correctness of the address identification carried out by the associated interface can be examined once more by the microcontroller after waking up of the same. However, with microcontrollers intended specifically for a data network with interfaces according to the invention, it is also possible to omit the address identification part since address filtering already takes place anyway in the interface arranged upstream thereof.
In a preferred embodiment, the individual interfaces are not only adapted to be awakened to their active state by the beginning of a message frame, but in addition thereto by an external wake-up signal. The latter may play a role, for example, when a data node belongs to one of the centrally lock
Heinrich Peter
Kuhls Burkhard
Iannucci Robert
SEED IP Law Group PLLC
STMicroelectronics GmbH
Wiley David
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