JP4570753B2 - Error code sending apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an error code transmitting apparatus and method, and more particularly to an error code transmitting apparatus and method for transmitting an error code to a network for communicating a message with an identification code between a plurality of modules.
[0002]
BACKGROUND OF THE INVENTION
An international standard (ISO11898) control area network (CAN) is known as a network connecting a plurality of modules such as an in-vehicle network, a home appliance network, and an industrial control device network. The CAN transmission rate is up to 1 Mbps, which is much faster than conventional communication methods. Serial communication that replaces high and low digital signals with differential voltages between two wires on the network, providing excellent noise resistance. Another feature is that the CAN controller automatically performs most network anomaly detection and recovery operations.
[0003]
In the case of an in-vehicle network, examples of the connected module include an engine controller, a meter panel controller, and a transmission controller. These modules have a relationship that their own control target cannot be controlled without knowing the status of the control target of other modules. Therefore, it is necessary to exchange data between modules at high speed. CAN is effective to connect these modules in equal and parallel fashion.
[0004]
CAN is a bus system with multi-master capability, and all CAN modules can transmit data on the bus. Multiple CAN modules can simultaneously receive bus signals (broadcasting). In a CAN network, there is no so-called station ID in principle. Instead, a message is identified by a message ID which is an identification code. Each module has a filtering function that processes whether or not a message should be formally captured based on the received ID. The message ID also determines the priority when bus accesses from a plurality of modules compete. As a result of the line contention, only messages from modules that have won communication arbitration appear on the bus.
An example of one module connected to such a CAN network is shown in FIG. When receiving data on the bus, the CAN transceiver 2 receives the message represented by the differential voltage signal on the bus 1 and converts it into a binary digital signal (L, H), and the CAN controller. Send to 3. When transmitting data to the bus, the CAN transceiver 2 converts the binary digital signal from the CAN controller 3 into a differential voltage signal and sends it to the bus 1. More specifically, in the case of a high-speed system with a maximum of 1 Mbps, the digital high signal corresponds to a potential difference of −1.0 V to +0.4 V (recessive) on the CAN bus, and the digital low signal corresponds to a potential difference on the CAN bus. Corresponds to + 1.0V to + 5.0V (Dominant). For fault-tolerant systems up to 125 Kbps, a digital high signal corresponds to a potential difference of -5 V to -3.2 V (recessive) on the CAN bus, and a digital low signal is a potential difference of -2.5 V to +5.0 V on the CAN bus ( Equivalent to Dominant). However, these potential differences differ slightly depending on the type of transceiver.
[0005]
When the ID of the received message, that is, the identification code indicates that it is a message to be received, the CAN controller 3 stores the message in the message buffer 5 and notifies the arithmetic unit 4 with an interrupt signal. The computing device 4 performs a predetermined process using the message. When the arithmetic unit 4 supplies data to the bus, the ID and transmission data are written in the message buffer 5 and transmitted via the CAN transceiver. The CAN controller follows the standard and automatically places data on the bus line when the bus is free. All other modules can receive this data on the bus line.
[0006]
If an error occurs in a message, the CAN controller 3 that has received the message detects the error. When an error is detected, the CAN controller 3 sends a 14-bit error frame onto the bus. The error frame format is standardized by CAN, and is an error flag for 6 bits and an error delimiter for 8 bits. Specifically, the error flag depends on the error detection status of the module, and means 6-bit continuous dominant in the normal state (error-active), and 6-bit in the error state (error-passive). Means continuous recessive. The error delimiter means an 8-bit continuous recessive signal. If multiple modules provide different signals on the bus, the bus will always be in a dominant state if there is even one dominant. This is because the recessive signal for 8 bits after the dominant signal for 6 bits makes it possible to identify the next frame. If not all modules have detected an error and one module has not detected an error, the module that has not detected the error will receive an error frame sent by the module that has detected the other error. For the first time, it is recognized as an error and an error frame is transmitted. That is, after detecting an error frame, an error frame is transmitted. As described above, on the bus, if the transmission of error frames is temporally shifted from each other, the total length of the apparent error frame becomes long. Therefore, it is better to consider that the apparent error frame appearing on the bus is a maximum of 20 bits instead of 14 bits.
[0007]
For a certain message, an error frame is transmitted from any of the received modules, and when the transmitting side that transmitted the message receives the error frame, the transmitting side stops message transmission. Wait until the next transmission is possible, then resend. The transmission side has an error counter, and when the value of the counter increases to a threshold value (that is, the number of errors exceeds the threshold value), the bus is automatically turned off.
[0008]
[Problems to be solved by the invention]
The conventional modules as described above have functions such as normal message transmission / reception and error occurrence monitoring. When a module developer creates a program to handle an error and validates it, an error must occur. However, since errors usually do not occur, errors must be deliberately generated. Conventionally, there has been a method of mixing noise such as a sine wave on a bus in order to verify an error that occurs in a poor communication line situation. However, in the method of mixing noise on the bus, communication messages from all modules are targeted, and it is not possible to put only a specific module or only a specific message into an error state.
[0009]
Therefore, an object of the present invention is to provide an error code transmission apparatus and method that can set only a specific module or a specific message to an error state.
[0010]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a module 10 similar to the conventional one and an error code sending device 20 according to one embodiment of the present invention. These may be formed integrally or separately. Normally, the switching circuit 30 is connected to the CAN controller 3 side, and when a normal message or a message including an error is received, normal processing similar to that in FIG. 1 is performed.
[0011]
When it is desired to detect an error relating to a message by changing a message having a predetermined identification code to an error state, the error code transmission device of this embodiment is effective. The data received by the CAN transceiver 2 is converted into digital binary output serial data and supplied to the CAN module 10 and the error code sending device 20. The identification code detection element 21 receives the serial digital data from the CAN transceiver 2 and detects and stores the identification code. If the identification code is an 11-bit digital code, the identification code detection element 21 includes an 11-bit register.
[0012]
The identification code register 23 receives the supply of the identification code of the message to be put into an error state from the arithmetic unit 4 and stores it. For example, it may be an 11-bit register. The identification code register may further include a wild card register 25. The comparator 22 compares the identification code stored in the identification code register 23 with the identification code stored in the identification code detection element 21, and outputs a coincidence signal when these codes completely match. If it is desired to put an entire message group in an error state instead of a single message, a match signal may be output when only a part of the identification code matches. At this time, for example, the wild card register 25 is useful. Of the 11-bit wildcard register, for example, a bit containing 1 can be regarded as matching both identification codes regardless of the values of the identification code detection element 21 and the identification code register 23. For example, a coincidence output may be output when all the bits of the result expressed by a logical expression such as (detected identification code XNOR stored identification code) OR wildcard register become 1.
[0013]
In response to the coincidence output from the comparator 22, the error frame generator 26 generates the error frame and the switching control signal as described above and outputs them to the switching circuit 30. Not only the error frame but any signal or code whose target message is interpreted as invalid (error) may be used. These are collectively referred to as error codes. In response to the switching control signal, the switching circuit 30 switches the output to the CAN transceiver from the CAN controller 3 side to the error frame generator 26 side. As a result, the error code from the error frame generator 26 is sent to the bus 1 via the CAN transceiver 2.
[0014]
The coincidence output is also sent to the interrupt control circuit 27 to inform the arithmetic unit 4 that an error frame will be transmitted.
[0015]
When the module that sent the message that has been changed to the error state (the module that sent the message that is subject to error code transmission (marking)) receives the error code on the bus, it can enter the procedure for transmission error detection and processing The initial objective is achieved.
[0016]
The present invention is of course applicable to any network other than CAN. In the case of CAN, since the CAN controller automatically transmits and receives data and the degree of freedom is low, the error code transmission device of the present invention is particularly useful.
[0017]
[Effects of the embodiment]
Since the embodiment of the present invention is configured as described above, a module or message that transmits a specific identification code can be put into an error state by the error frame marking function. As a result, it is possible to verify the abnormal processing (error recovery processing) of the software operating on the module that could not be normally performed.
[0018]
According to the present embodiment, a message with a specific identification code can be invalidated (error), and a module that has transmitted the message can be placed in a transmission error state. Since a message with a specific identification code can be invalidated (error), there is a module that needs the invalidated message, that is, receives data in this message and performs internal processing based on that data. If this is the case (receiving module), the module will be in a situation where no specific data (message) is entered. In other words, it is possible to intentionally create a situation where specific data does not enter among multiple required data, and to verify the abnormal processing to cope with such a situation. Is possible.
Furthermore, since the module that transmitted the message can be put into a transmission error state, it is possible to intentionally increase (count up) the transmission error counter.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of a conventional CAN module.
FIG. 2 is a block diagram showing an error code transmission device according to an embodiment of the present invention together with a conventional CAN module.
[Explanation of symbols]
10 Error Code Sending Device 23 Identification Code Register 21 Identification Code Detection Element 22 Comparator 26 Error Code Generator 25 Wild Card Register 27 Interrupt Control Circuit

Claims (5)

An error code sending device for sending an error code to a network for communicating a message with an identification code between a plurality of modules:
An identification code register for storing a desired identification code in advance;
An identification code detecting element for receiving and detecting the identification code from the network and storing it;
A comparator that compares the identification code in the identification code register with the identification code in the identification code detection element and outputs a coincidence signal when at least part of the identification code coincides; and responds to the coincidence signal from the comparator An error code generator that sends an error code to the network;
An error code sending device comprising: The apparatus of claim 1, wherein the network is a control area network. 3. The apparatus according to claim 2, further comprising a transceiver provided between the identification code detecting element and the error code generator and a network. The identification code register comprises a wildcard register;
The comparator compares an identification code in the identification code register with an identification code in the identification code detection element, and outputs a coincidence signal when a predetermined part is coincident. Item 1. The apparatus according to Item 1. A method for sending an error code to a network for communicating messages with identification codes between multiple modules:
Storing a desired identification code in advance;
Receiving, detecting and storing the identification code from the network;
Comparing the pre-stored identification code with the received and stored identification code and outputting a coincidence signal when at least part of the identification codes coincide;
Sending an error code to the network in response to the match signal;
A method characterized in that it can be made into an error state apparently without any error.

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