JP5532030B2 - Data communication method and data communication apparatus - Google Patents

Description

  The present invention relates to a data communication method and a data communication apparatus for communicating a frame including data.

  Conventionally, CAN (Controller Area Network), for example, has been widely used as an in-vehicle LAN (Local Area Network) that requires high reliability (see, for example, Patent Document 1). In CAN, reliability is ensured by detecting stuff error, bit error, form error, acknowledge error, CRC (cyclic redundancy check) error, etc. at data communication speeds of 500 kbps or less. ing.

Japanese Patent No. 2546608

  In recent years, with the advancement of communication systems, high data communication speed (several hundred M [bps]) and high reliability tend to be required, and non-collision and clock recovery necessary for high data communication speed are required. When the communication system is used, CAN has a problem that sufficient reliability cannot be ensured due to a difference in frame configuration.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a data communication method and a data communication apparatus that can ensure high reliability while increasing the data communication speed. .

According to the first and second aspects of the present invention, a link layer frame including data is 4B5B-encoded, and a preamble, a frame start unit, and a frame end unit are added to the 4B5B-encoded link layer frame to add a physical layer. When generating a frame, encoding the generated physical layer frame with NRZI (Non Return to Zero Inversion), and transmitting the NRZI-coded physical layer frame as a transmission frame to the communication path, the physical layer frame is parallel / serial. Whether the transmission data is normal by collating the data before conversion and NRZI conversion with the data after SFD detection and serial / parallel conversion of the physical layer frame of the NRZI code received from the communication path Bit error detection is performed to determine the received frame from the When a physical layer frame is received, coding error detection is performed to determine whether 4B5B encoding is normal for the received physical layer frame, and whether the data included in the link layer frame is normal CRC (Cyclic Redundancy Check) error detection is performed, form error detection is performed to determine whether the configuration and contents of the link layer frame are normal, and the bit sequence of the link layer frame is normal State error detection is performed to determine whether or not an ACK (ACKnowledgement) frame is normally received within a predetermined time, and timeout error detection is performed to determine whether or not the frame has been normally received within a predetermined time.

  As a result, a handshake communication method using an ACK frame for realizing non-collision is adopted, a link layer frame is 4B5B encoded, a preamble, a frame start part and a frame end part are added to the link layer frame, The data communication speed can be increased by adding the clock recovery requirement that the layer frame is NRZI encoded. Also, when transmitting a transmission frame to the communication path, bit error detection is performed. When a reception frame is received from the communication path, coding error detection, CRC error detection, form error detection, state error detection, and timeout error are detected. By performing detection, high reliability can be ensured.

Functional block diagram showing an embodiment of the present invention The figure which shows each frame structure of a link layer frame and a physical layer frame Diagram showing function hierarchy Diagram showing comparison with OSI reference model Flow chart showing error detection processing during data transmission Flow chart showing error detection process at data reception Diagram showing error type, detection mode, and error content

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram showing the configuration of the data communication apparatus. The data communication apparatus 1 includes a transmission LLF (Link Layer Frame) encoder 2, a FIFO (First In First Out) 3, a 4B5B encoder 4, a 5N-bit command encoder 5, and a control circuit 6 as transmission system functional blocks. , Selector 7, serializer 8, and NRZI encoder 9.

  The transmission LLF encoder 2 receives transmission data from the transmission / reception sequencer 10 (corresponding to state error detection means and timeout error detection means in the present invention), an identifier for identifying (specifying) a frame, and data writing or reading. A link layer frame (LLF (Link Layer Frame)) including a remote indicating the ID, a size indicating the length of the data, an ID indicating the address space to be accessed, data (transmission data), and a CRC is generated to generate a FIFO 3 To the 4B5B encoder 4 and the 5N-bit command encoder 5.

  When the 4B5B encoder 4 inputs the link layer frame from the transmission LLF encoder 2 via the FIFO 3 as an 8-bit bit string, each of the upper 4-bit bit string and the lower 4-bit bit string constituting the 8-bit bit string is received. A 5-bit bit string is converted according to a 4B5B encoding table (not shown), and a 10-bit bit string is generated and output to the selector 7. In this case, the 4B5B encoder 4 converts the 4-bit bit string into a 5-bit bit string so that “0” does not continue for 3 bits or more.

  When a link layer frame is input from the transmission LLF encoder 2 via the FIFO 3, the 5N-bit command encoder 5 receives a preamble (Preamble) that is a synchronization bit string and an SFD (Start Frame Delimiter) for detecting the head of the link layer frame. (Frame start part) and EFD (End Frame Delimiter) (frame end part) for detecting the end of the link layer frame are generated and output to the control circuit 6 and the selector 7.

  The selector 7 inputs a 10-bit bit string from the 4B5B encoder 4 and inputs a preamble, SFD, and EFD from the 5N-bit command encoder 5, and then, according to a control command input from the control circuit 6, the preamble, SFD, The EFD is added to generate a physical layer frame (PLF (Physical Layer Frame)) and output to the serializer 8 and the bit error detection unit (data comparison unit) 11 (corresponding to the bit error detection means in the present invention).

  When the physical layer frame is input from the selector 7, the serializer 8 performs parallel / serial conversion on the physical layer frame and outputs it to the NRZI encoder 9. When the NRZI encoder 9 receives a physical / layer-converted physical layer frame from the serializer 8, the NRZI encoder 9 encodes the physical layer frame into an NRZI code and transmits it as a transmission frame from the transmission terminal to the communication path.

  On the other hand, the data communication apparatus 1 includes a clock recovery unit 12, an NRZI decoder 13, an SFD (Start Frame Delimiter) detection unit 14, a deserializer 15, and a 4B5B decoder 16 (coding in the present invention) as reception-system functional blocks. Error detection means), a selector 17, a control circuit 18, a FIFO 19, and a reception LLF decoder 20 (corresponding to form error detection means and CRC error detection means in the present invention).

  The clock recovery unit 12 extracts a clock component from the physical layer frame of the NRZI code received as a reception frame from the communication path, recovers the clock signal, and supplies the recovered clock signal to each functional block. The NRZI decoder 13 decodes the physical layer frame of the NRZI code received as a received frame from the communication path, and outputs the decoded frame to the SFD detection unit 14.

  When the physical layer frame is input from the NRZI decoder 13, the SFD detection unit 14 detects the SFD included in the physical layer frame, detects the head of the link layer frame, and outputs the link layer frame to the deserializer 15. When receiving the link layer frame from the SFD detection unit 14, the deserializer 15 performs serial / parallel conversion on the bit string of the link layer frame and outputs the bit sequence to the 4B5B decoder 16 and the bit error detection unit 11. The 4B5B decoder 16 reverse-converts the 10-bit bit string of the link layer frame serial / parallel converted from the deserializer 15 into an 8-bit bit string in accordance with a 4B5B encoding table (not shown), and sends it to the selector 17 and the control circuit 18. Output.

  When the selector 17 receives the 8-bit bit string of the link layer frame from the 4B5B decoder 16, the selector 17 outputs the link layer frame to the reception LLF decoder 20 via the FIFO 19 in accordance with a control command input from the control circuit 18. When receiving the 8-bit bit string of the link layer frame from the selector 17 via the FIFO 19, the reception LLF decoder 20 outputs the 8-bit bit string of the link layer frame to the transmission / reception sequencer 10.

  The frame configuration of the link layer frame and the frame configuration of the physical layer frame have a correspondence relationship as shown in FIG. Further, as shown in FIG. 3, the data communication apparatus 1 can be divided into a physical layer, a link layer, and an API (Application Program Interface) layer by dividing its function into a hierarchical structure. ) It can be divided into a functional unit that performs control and a functional unit that performs reception (RX) control. The physical layer, link layer, and API layer shown in the present embodiment are compared with the OSI (Open Systems Interconnection) Reference Model established by the International Organization for Standardization (ISO), as shown in FIG. Corresponds to the first layer (physical layer) of the OSI reference model, the link layer corresponds to the second layer (data link layer) and the third layer (network layer) of the OSI reference model, and the API layer corresponds to the OSI reference model. This corresponds to the fourth layer (transport layer), the fifth layer (session layer), and the sixth layer (presentation layer). The link layer frame is logically communicated between the link layers of the data communication apparatus 1, and the physical layer frame is physically communicated between the physical layers of the data communication apparatus 1.

  The data communication apparatus 1 described above has an error detection function described below, and performs error detection processing at the time of data transmission at the time of data transmission and performs error detection processing at the time of data reception at the time of data reception. Hereinafter, the error detection process at the time of data transmission and the error detection process at the time of data reception will be described sequentially.

(1) Error detection processing during data transmission The data communication device 1 performs error detection processing during data transmission shown in FIG. 5 during data transmission. That is, the data communication apparatus 1 performs bit error detection in the bit error detection unit 11 for determining whether or not the transmission data is normal (step S1). The data communication device 1 collates the data included in the physical layer frame input from the selector 7 to the bit error detection unit 11 and the data included in the link layer frame input from the deserializer 15 to the bit error detection unit 11. When data different from the transmission data is detected or when transmission data is not detected, it is determined that the transmission data is not normal (“YES” in step S1), and it is detected that a bit error has occurred. (Step S2). As described above, the data communication apparatus 1 performs bit error detection when transmitting data.

(2) Error detection process at the time of data reception The data communication apparatus 1 performs the error detection process at the time of data reception shown in FIG. 6 at the time of data reception. That is, the data communication apparatus 1 performs coding error detection in the 4B5B decoder 16 for determining whether or not 4B5B encoding is normal (step S11). The data communication apparatus 1 determines an 8-bit bit string obtained by inversely converting the 10-bit bit string of the link layer frame input from the deserializer 15 to the 4B5B decoder 16 according to the 4B5B coding table, and other than the bit string shown in the 4B5B coding table When the bit string (undefined bit string) is detected, it is determined that the 4B5B encoding is not normal (“YES” in step S11), and it is detected that a coding error has occurred (step S12).

  Next, the data communication apparatus 1 performs CRC (Cyclic Redundancy Check) error detection in the reception LLF decoder 20 for determining whether or not the data included in the link layer frame is normal (step S13). The data communication apparatus 1 performs calculation by the reception LLF decoder 20 on the 8-bit bit string of the link layer frame input from the selector 17 via the FIFO 19 to the reception LLF decoder 20, and based on the CRC calculation expression. If an error is detected in the calculation, it is determined that the data included in the link layer frame is not normal (“YES” in step S13), and it is detected that a CRC error has occurred (step S14).

  Next, the data communication apparatus 1 performs form error detection in the reception LLF decoder 20 for determining whether or not the configuration and contents of the link layer frame are normal (step S15). When the data communication apparatus 1 determines the 8-bit bit string of the link layer frame input from the selector 17 to the reception LLF decoder 20 via the FIFO 19 and detects reception of a link layer frame different from the condition of the reception header. Then, it is determined that the configuration and contents of the link layer frame are not normal (“YES” in step S15), and it is detected that a form error has occurred (step S16).

  Next, the data communication apparatus 1 performs state error detection in the transmission / reception sequencer 10 for determining whether or not the arrangement of the bit string of the link layer frame is normal (step S17). When the data communication apparatus 1 detects reception of a link layer frame that is different from the normal sequence, it determines that the bit sequence of the link layer frame is not normal (“YES” in step S17), and a state error has occurred. This is detected (step S18).

  Finally, the data communication apparatus 1 performs timeout error detection in the transmission / reception sequencer 10 for determining whether or not the ACK frame is normally received within a predetermined time (step S19). After transmitting the data frame, burst frame, and command frame, the data communication apparatus 1 sends a response (ACK frame) to the transmitted data frame, burst frame, and command frame, and determines when the data frame, burst frame, and command frame are transmitted. If it is not detected within the predetermined time as the reference time, it is determined that the ACK frame has not been normally received within the predetermined time (“YES” in step S19), and it is detected that a timeout error has occurred ( Step S20). As described above, the data communication device 1 sequentially performs coding error detection, CRC error detection, form error detection, state error detection, and timeout error detection when receiving data.

  FIG. 7 shows the above-described error types, detection nodes (transmission nodes or reception nodes), and error contents in association with each other. The transmission node is a data communication device 1 that transmits a transmission frame, and the reception node is a data communication device 1 that receives a reception frame.

  As described above, according to the present embodiment, the data communication apparatus 1 adopts the handshake communication method using the ACK frame for realizing the non-collision, and the link layer frame is 4B5B encoded to form the link layer frame. On the other hand, by adding a preamble, SFD, and EFD, and adding a clock recovery requirement of NRZI encoding of the physical layer frame, the data communication speed can be increased. Also, when transmitting a transmission frame to the communication path, bit error detection is performed. When a reception frame is received from the communication path, coding error detection, CRC error detection, form error detection, state error detection, and timeout error are detected. By performing detection, high reliability can be ensured.

The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
The data communication apparatus 1 may be a node connected to an in-vehicle LAN, for example, or may be a node connected to a LAN other than the in-vehicle LAN.

  In the drawing, 1 is a data communication device, 10 is a transmission / reception sequencer (state error detection means, timeout error detection means), 11 is a bit error detection unit (bit error detection means), 16 is a 4B5B decoder (coding error detection means), 20 Is a reception LLF decoder (form error detection means, CRC error detection means).

Claims (2)

A link layer frame including data is 4B5B encoded, a preamble, a frame start part, and a frame end part are added to the 4B5B encoded link layer frame to generate a physical layer frame, and the generated physical layer frame is converted to NRZI. (Non Return to Zero Inversion) Encoding and transmitting the NRZI-encoded physical layer frame as a transmission frame to the communication path, the data before the parallel / serial conversion and NRZI conversion of the physical layer frame, and the communication path The received physical layer frame of the NRZI code is compared with the data after SFD detection and serial / parallel conversion to detect bit error to determine whether the transmission data is normal, and receive from the communication path When a physical layer frame is received as a frame The CRC (Cyclic Redundancy) is used to detect whether or not the data included in the link layer frame is normal by performing coding error detection for determining whether the 4B5B encoding is normal for the received physical layer frame. Check) Error detection, form error detection to determine whether the structure and contents of the link layer frame are normal, and state error detection to determine whether the bit sequence of the link layer frame is normal And performing time-out error detection for determining whether or not an ACK (ACKnowledgement) frame has been normally received within a predetermined time. A link layer frame including data is 4B5B encoded, a preamble, a frame start part, and a frame end part are added to the 4B5B encoded link layer frame to generate a physical layer frame, and the generated physical layer frame is converted to NRZI. (Non Return to Zero Inversion) A data communication device that encodes and transmits the NRZI-encoded physical layer frame as a transmission frame to a communication path,
Transmission data by collating the data before parallel / serial conversion and NRZI conversion of the physical layer frame with the data after SFD detection and serial / parallel conversion of the physical layer frame of the NRZI code received from the communication path A bit error detection means for performing bit error detection for determining whether or not is normal,
Coding error detection means for performing coding error detection for determining whether or not 4B5B encoding is normal for a physical layer frame received as a reception frame from a communication path;
CRC error detection means for performing CRC (Cyclic Redundancy Check) error detection for determining whether or not the data included in the link layer frame is normal;
Form error detection means for performing form error detection for determining whether the configuration and contents of the link layer frame are normal;
State error detection means for performing state error detection for determining whether or not the bit sequence of the link layer frame is normal;
A data communication apparatus comprising: a timeout error detection means for performing a timeout error detection for determining whether or not an ACK (ACKnowledgement) frame has been normally received within a predetermined time.

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