WO1999034560A1

WO1999034560A1 - Interface for several can data-processing networks and method for operating an interface

Info

Publication number: WO1999034560A1
Application number: PCT/EP1998/008431
Authority: WO
Inventors: Rolf Wilhelm Kemper; Ralf Usling; Jens Kurt Eltze
Original assignee: Nec Electronics (Europe) Gmbh
Priority date: 1997-12-29
Filing date: 1998-12-23
Publication date: 1999-07-08
Also published as: DE19758032A1

Abstract

The invention relates to an interface for linking at least two CAN (Controller Area Network) networks to respectively distributed CAN computer nodes. An interface of this type is used to transmit information from one CAN network to another. According to the invention, the interface has a central memory for storing information, each of the CAN networks being allocated its own memory area. This minimises the burden on the central processing unit and makes the interface more flexible for interfacing other networks. The interface is preferably also provided with its own, extra machine bus and a memory access control system to relieve the central processing unit of the additional burden of managing memory accesses.

Description

Interface for several CAN data processing networks and method for operating an interface

The invention relates to an interface (controller) according to the preamble of claim 1 and a method for operating the interface.

Data processing systems with distributed computer nodes that are connected via a serial data bus are mainly used in industrial and automotive local networks. The computer nodes include data processing devices or signal processing devices that are designed for a specific application. This includes data exchange between control units, sensors and actuators.

An example of the data processing systems defined above is the Controller Area Network (CAN), which currently works with a standard protocol, 2nd OB.

Each CAN unit, ie each computer node, is connected to all other computer nodes via a serial data bus, and essentially two different "levels" are defined for CAN, namely a protocol level and one, for the exchange or management and processing of data Object level. Data is exchanged between the CAN units in the form of so-called "notification objects". In this case includes a "Communication object" in addition to the actual data to be processed, yet ^'' for example, an identification field (ID), status fields, fields for clock control, etc. For the purposes of this application, the term "level" both an implementation by software than also through hardware as well as through combinations of both. 1 shows the schematic structure of a CAN unit. The protocol level 1 is shown, which is connected to an external CAN bus 5 and is responsible for the correct handling of data on the CAN bus. In particular, message objects are checked for correct data format, and incoming message objects are converted from serial data format to parallel data format.

The adjoining object level 2 is used for filtering data, and in particular for data management, and forms the interface between the protocol level and a CAN memory 3. The object level takes over the data management and the storage of data and outputs the necessary data to a memory 3 control unit, not shown.

The CAN memory 3 is normally connected directly to the object level and, for example in the case of the “fill CAN”, is designed as RAM with two inputs (dual port). The illustration in FIG. 1 is only a rough schematic structure. In fact, the functions can be shifted between the object level and the protocol level, and a clear separation is often not possible. An example of a known CAN system is shown in DE-A-4140017, the disclosure of which is expressly incorporated by reference here.

In the field of automotive technology, there is an increasing need to set up a control system with more than one network, for example a network for the motor control and a network for the so-called "body electronics" such as window regulators, lighting, etc. However, this also makes it necessary to do so Providing interfaces in order to be able to exchange data between the individual networks, for example in the case of a combined anti-slip and ABS control. Possible realizations of a Such an interface are shown in Figures 2 and 3.

In Fig. 2 the "classic" way is shown to exchange data between different networks. The interface 20 shown in FIG. 2 each comprises two CAN units 10, 10 ', which are connected to different networks via their assigned buses 5 and 5'. Each of the CAN units 10, 10 'essentially corresponds in structure to the unit 10 shown in FIG. 1. The units are connected to one another via an internal bus 4, and a central processor unit (CPU) 100 is additionally provided. The data are read by the CPU from the first CAN unit 10 and then written into the other unit 10 '. This means that the CPU load is dependent on the number of data transfers, the number of bytes to be transferred, etc.

An alternative embodiment, which is not prior art, is shown in FIG. 3. In addition to the areas in FIG. 2, a bridge module 12 is also provided, which supports data transfer. The bridge module could be implemented as a hardware implementation, and the mode of operation of the bridge module for the direct data transfer between two CAN units must be specified depending on the application. Often, CPU activity is also required, since not all transmission mechanisms can be implemented using such a bridge.

Furthermore, it should be noted that in order to implement the approaches shown in FIGS. 2 and 3, it is assumed that the individual CAN units 10, 10 'are copied to implement the interface; ie the layout of the CAN unit is copied onto a chip (die) according to the number of different connections (networks). All units such as the protocol level, the object level and the message object memory are copied and removed. interconnected according to the interface size (ie depending on the number of inputs and outputs). However, this requires a separate configuration for each interface depending on the number of CAN units, and the entire layout must be changed if the structure is changed. Finally, the expansion of the interface with additional CAN units places a limit on the CPU load.

In contrast, the invention has for its object to develop an interface of the type mentioned, in which the load on the central processor unit is largely minimized and which is characterized by high flexibility; a method for operating such an interface is also to be specified.

This object is achieved in that a central message object memory is provided, and a memory area can be assigned to each input / output unit (CAN unit).

It is therefore not necessary to design a separate memory for each CAN unit, which, depending on the size, would have to be designed depending on the CAN units of the respective network. Depending on the memory area actually required, as much memory space can be allocated in the central memory as is required for the implementation in question. To expand the interface for connecting a further data network, therefore, only additional storage space has to be identified or existing storage space has to be rededicated, and the protocol and the object level for an input / output unit have to be created.

In addition to the internal bus that connects the CPU to the input / output units, a machine bus is preferably provided, via which the data transfer between the input / output units and the CPU on the one hand and the central memory on the other hand.

A central memory access control is preferably provided, which controls all data transfers from and to the memory.

Each input / output unit preferably comprises a protocol level and an object level.

The central message object memory is preferably designed as a content-addressable memory (CAM) and / or as a free access memory (RAM); In addition, an event sequence memory can also be provided, in which a sequence is recorded which is to be triggered when a change in status of a notification object is determined.

In order to facilitate the data exchange between individual input / output units, at least one bridge module is preferably provided, which is connected between the machine bus and the internal bus in the same way as the input / output units. On the basis of data that is stored in the message object memory and / or depending on status changes of message objects, the bridge module can copy data from one memory area into another memory area or transfer it there.

Overall, a modular construction of the interface is thus achieved according to the invention, in which various units of the interface are designed as modules which are only connected between the internal bus and the machine bus. The modules can be designed as CAN modules (input / output unit) with protocol and object level or as bridge modules for transmitting data between the networks. Finally, it is also possible to implement self-defined functional modules in the same way; by using an event Follow-up control can trigger, for example, the change of a notification object (event) a certain sequence (action).

Each memory access is made via the central memory access control, so that there is complete control over all storage processes.

According to the invention, each module (input / output unit, bridge module, function module, etc.) is assigned its own machine number, and the notification object of each individual network is supplemented by the machine number. In this way, it is very easy to assign each individual notification object within the interface to the corresponding data processing network (CAN network). The corresponding memory area can also be assigned for each individual module. This proves to be particularly advantageous when using a content-addressable memory (CAM) in which at least part of the message object, preferably the machine number and the identification field, is stored; remaining data such as semaphores, status fields etc. can be saved in a correspondingly assigned RAM.

Embodiments of the invention are explained with reference to the accompanying drawings. Show it:

FIG. 1 shows the schematic structure of a CAN node,

FIG. 2 shows the structure of a conventional interface,

FIG. 3 shows a possible approach for simplifying data transmission between CAN units,

Figure 4 shows the schematic structure of an interface according to the invention and

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Semaphores are bit sequences that indicate states of message objects (for example, topicality, etc.). The time stamp is used to synchronize different data processing networks, and with regard to the details of clock synchronization, reference is made to DE-A-4140017 mentioned at the beginning.

In addition to the actual data field, an event sequence field is also provided according to the invention. The event sequence field refers to a memory area of an event sequence memory when the state of the semaphore changes. For example, it can be provided in the memory 50 ₃ that when a certain event occurs (state change of a semaphore of a message object) a certain sequence should occur, e.g. change of another message object or generate a new message object, ^* such as by arrows B and A in Figure 5 is shown.

In this way, a loop of sequences of events can also be triggered, as shown by the arrow C in Figure 5. If, for example, a notification object changes, the event list in RAM 50 ₂ refers to a corresponding sequence (action) ACT1 in event sequence memory 50 ₃ ; wherein the action ACT1 ... ACTN specified in the memory 50 ₃ again causes the change of a notification object, which again represents an event. In this way, complex control sequences can also be implemented in a simple manner.

As previously mentioned, central memory access controller 40 controls access to the message object memory, preferably according to an access plan. That is, the memory access controller provides each module and the CPU 100 with a time window for the memory access. to CL N CD Φ TI σ y- ι_ι. £ ISJ rr rt ISI to N Φ SU CL <2, -, rt td tr s; £ N ISI CL TI ≤ rt £ μ- SU: μ- y- ¹ £ φ Φ Φ φ Φ μ-

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All controls as well as bridge modules, self-defined modules, event sequence control can be implemented via hardware, so that the load on the CPU is significantly reduced.

Claims

claims

1. Interface for coupling at least two CAN networks, each with distributed CAN computer nodes with at least two input / output units for exchanging message objects with the CAN networks and an internal bus, via which the input / output units connect to one another stand, characterized by a central memory for storing message objects, wherein a memory area can be assigned to each input / output unit.

2. Interface according to claim 1, provided by an additional machine bus which is connected to the individual input / output units and the message object memory.

3. Interface according to claim 1 or 2, provided by a central memory access controller which controls access to the central message object memory.

4. Interface according to claim 1, 2 or 3, provided by a central processor unit which is connected to the individual input / output units and the central message object memory.

5. Interface according to one of claims 1 to 4, characterized in that each input / output unit has a protocol level for checking the data format of message objects and an object level for managing message objects.

6. Interface according to one of claims 1 to 5, characterized in that the notification object memory has a content-addressable memory (CAM) and / or a free access memory (RAM).

7. Interface according to one of claims 1 to 6, g e k e n n z e i c h n e t by an event sequence memory.

8. Interface according to claim 7, characterized in that the event sequence memory is part of the central message object memory.

9. Interface according to one of claims 1 to 8, g e k e n n z e i c h n e t by at least one bridge module, which is connected to the internal bus and the machine bus and exchanges message objects between different input / output units.

10. Interface according to one of claims 1 to 9, characterized in that each input / output unit, each bridge module and possibly self-defined functional unit is constructed as a module which is connected between the internal bus and the machine bus.

11. Interface according to claim 10, characterized in that the memory access of each unit, each module or the CPU takes place via the central memory access control.

12. A method for operating an interface according to one of claims 1 to 11, wherein each input / output unit can exchange message objects with its associated CAN network, characterized in that each input / output unit and each bridge module is assigned a machine number and the notification objects expanded by the machine number.

13. The method according to claim 12, characterized in that the machine number and an identification field of the notification object are stored in a content-addressable memory and further fields in a free access memory.

14. The method according to claim 13, characterized in that semaphores and event sequence fields are contained in the further data fields of the notification objects, the event sequence field indicating a sequence which is triggered when the state of the semaphores changes .

15. The method according to claim 14, characterized in that the event sequence field has a reference to a storage location in an event sequence memory.

16. Data processing system with at least two data networks with distributed computer nodes and with an interface according to one of claims 1 to 11.