JP2013058845A - Data communication method and data communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data communication method and a data communication system which are able to detect an error of a control information part in a communication frame.SOLUTION: Communication is performed by use of a communication frame comprising a header including a control code, a data part comprised of transmission data, and an error detection part comprised of a CRC code. When a transmission side transmits data in which an error detection code for control to perform error detection of the header is included in the error detection part, a reception side performs error detection of the header based on the error detection code for control, and therefore, it is possible to detect occurrence or no-occurrence of an error of the header based on the CRC code by performing error detection of the header based on the error detection code for control.

Description

  The present invention relates to a data communication method and a data communication system for performing communication using a communication frame including at least a control information unit including an ID of a communication destination, a data unit including transmission data, and an error detection unit including an error detection code. .

  In data communication, an error detection code such as a CRC (Cyclic Redundancy Check) code is added to a communication frame for transmission, and the reception side performs error detection on the received data using the error detection code, and an error is detected. Then, a request for retransmission of the communication frame is made (see, for example, Patent Document 1).

Japanese Patent No. 3274655

  However, error detection as described above is performed only on data, and it is assumed that error detection is performed because the number of bits for the header portion in the communication frame is small compared to the data portion. Not done.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a data communication method and a data communication system capable of detecting an error even with a control information portion in a communication frame. .

  According to the data communication method of the first aspect, communication is performed using a communication frame including a control information portion including at least a control code, a data portion including transmission data, and an error detection portion including an error detection code. Then, when the transmission side performs transmission by including a control error detection code for performing error detection for the control information unit in the error detection unit, the reception side performs control based on the control error detection code. Perform error detection. Therefore, the receiving side can detect whether or not an error has occurred in the control information section.

  According to the data communication method of claim 2, the transmitting side divides the data part into a plurality of unit data parts with a predetermined number of bits as a unit, and a plurality of error detection parts for performing error detection on the data part are provided. A plurality of units are provided corresponding to the unit data portion. Then, the receiving side performs error detection for each of the plurality of unit data parts. Therefore, an error can be detected for each unit data portion in a so-called burst transmission mode in which a plurality of unit data portions are transmitted in one transmission.

  According to the data communication method of claim 3, the transmission side performs error detection in the error detection unit by combining the control error detection code with the control information unit and the subsequent unit data unit. Generate. Therefore, an increase in the number of bits of the error detection code can be suppressed.

  According to the data communication method of claim 4, since the same type of error detection code is used for the control error detection code and the error detection code added to each of the plurality of unit data parts, the processing on the transmission side and the reception side is performed. It will be easy.

  According to the data communication method of claim 5, the receiving side requests the transmitting side to retransmit the portion in which the error is detected by the error detecting code, and the transmitting side requests that the retransmission request be received. Re-send the part. Therefore, even in the case of burst transmission with a long communication frame transmitted at a time, only the requested unit data part can be retransmitted, so that communication efficiency is improved.

  According to the data communication method of claim 6, the receiving side requests the transmitting side to change the number of bits of the error detection code in accordance with the frequency of retransmission request, and the transmitting side responds to the request. Change the number of bits of the error detection code. Therefore, the accuracy of error detection can be changed according to the communication environment.

  According to the data communication method of claim 7, when the transmission side performs 4B5B encoding as a communication layer as a link layer frame, a preamble, a frame start unit, and a frame end unit are added to the 4B5B encoded link layer frame. When a physical layer frame is generated and NRZI encoded and transmitted to a communication channel, bit error detection for determining whether transmission data is normal, whether the configuration and contents of the link layer frame are normal Form error detection to determine whether or not.

  On the other hand, the receiving side uses a coding error detection and error detection code to determine whether or not 4B5B encoding is normal for the received physical layer frame. Error detection to determine whether it is normal, form error detection to determine whether the structure and contents of the link layer frame are normal, and whether the bit sequence of the link layer frame is normal Perform state error detection. Further, the transmission side performs time-out error detection for determining whether or not the ACK frame has been normally received from the reception side within a predetermined time. Therefore, the reliability of communication can be further improved by combining error detection using an error detection code with various other error detections.

Functional block diagram showing the configuration of the data communication apparatus according to the first embodiment 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 The figure which shows the frame composition of each frame Diagram showing communication frequency, identifier length, and identifier of each frame The figure explaining the production | generation of a CRC code | symbol about a 12 bit ID burst frame 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 The figure explaining the process which requests retransmission of some data about a 12-bit ID burst frame The figure which shows the processing sequence between transmission and reception The figure which is 2nd Example and explains the change of the number of bits of a CRC code Figure equivalent to FIG. 1 equivalent diagram

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

  The transmission LLF encoder 2 receives transmission data from the transmission / reception sequencer 10 (corresponding to state error detection means and time-out error detection means), an identifier for identifying (specifying) a frame, a remote indicating data writing or reading, The size indicating the length of the data, the ID indicating the address space to be accessed, the data (transmission data), and the link layer frame (LLF) excluding the CRC code are generated and output to the selector 21 and the CRC calculator 22. . The CRC calculator 22 generates, for example, a 16-bit CRC code for the header (control information) portion and the data portion of the input link layer frame, and outputs the CRC code to the selector 21. Switching control of the selector 21 is performed by the transmission / reception sequencer 10, and by this switching, a link layer frame in which the CRC code is arranged at a predetermined position in the communication frame is generated and input to the FIFO 3. The link layer frame is input to the 4B5B encoder 4 and the 5N bit command encoder 5 via the FIFO 3.

  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.

  When the selector 7 receives a 10-bit bit string from the 4B5B encoder 4 and inputs a preamble, SFD, and EFD from the 5N-bit command encoder 5, the selector 7 outputs a preamble, SFD, When an EFD is added and a physical layer frame (PLF) is generated, it is output to the serializer 8 and the bit error detection unit (data comparison unit) 11 (corresponding to the bit error detection means).

  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 parallel / serial converted physical layer frame is input from the serializer 8, the NRZI encoder 9 encodes the physical layer frame into an NRZI (No Return to Zero Inversion) code and transmits it from the transmission terminal to the communication path as a transmission frame. .

  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 (as coding error detection means) as reception-system functional blocks. Equivalent), a selector 17, a control circuit 18, a FIFO 19, and a reception LLF decoder 20 (corresponding to form error detection means and code error detection means).

  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 inversely converts the 10-bit bit string of the link layer frame serial / parallel converted from the deserializer 15 into an 8-bit bit string according to a 4B5B encoding table (not shown), and outputs it to the selector 17 and the control circuit 18. To do.

  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, and the physical layer transmits (TX). It can be divided into a functional unit that performs control and a functional unit that performs reception (RX) control.

  When the physical layer, link layer, and API layer shown in this embodiment are compared with the OSI (Open Systems Interconnection) reference model established by the International Organization for Standardization (ISO), as shown in FIG. 4, the physical layer is the OSI reference model. 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 fourth layer (of the OSI reference model). It corresponds to the 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.

  Next, a procedure for determining the number of identifier bits (identifier length) to be allocated to the link layer frame will be described with reference to FIGS. Here, the frame having the highest communication frequency (usage frequency) in the communication network is a data frame having an ID length of a predetermined bit, the frame having the second highest communication frequency is an ACK frame, and the communication frequency is 3 It is assumed that the second highest frame is a command frame. Further, for example, assuming a communication system in which communication failure frequently occurs due to a severe noise environment such as a vehicle communication network (vehicle LAN (Local Area Network)) mounted on a vehicle, the communication frequency of the ACK frame is reduced. The second highest.

First, the data frame having the highest communication frequency in the communication network is determined. Specifically, the number of nodes (chips) connected to the communication path is Na, the address space required for the nodes is Nb, the coefficients are N, N1, and N2, and ^N1 that satisfies Na ≦ 2 N1 is obtained. Nb = 2 ^N2 satisfying N2 is obtained, and N = N1 + N2 is obtained. In this embodiment, N1 = 3 can be obtained when Na ≦ 8, and N = 12 can be obtained when N2 = 9. Therefore, a data frame having a 12-bit ID length (referred to as a 12-bit ID data frame) is determined as a data frame having the highest communication frequency.

  Next, the number of bits in the 12-bit ID data frame (remote length), the number of bits in size (size length), and the number of bits in ID (ID length) are specified, and the number of bits in the identifier (identifier length) The number of identifier bits is determined so that the sum of the number of bits in the remote, the number of bits in the size, and the number of bits in the ID is a multiple of 8 (8 bits, 16 bits, 24 bits, 32 bits, ...) To do.

  That is, in the 12-bit ID data frame, as shown in FIG. 5, the remote bit number is “1”, the size bit number is “1”, and the ID bit number is “12”. The number of bits of the identifier is determined to be “1” so that the sum of the number of bits of the size and ID (which correspond to the control code) is the latest multiple of 8 (in this case, “16”). As shown in FIG. 6, it is determined to be “0”.

  Next, the number of identifier bits to be assigned to the ACK frame having the second highest communication frequency after the 12-bit ID data frame is determined. That is, in the ACK frame, since the number of ACK bits indicating a response to the request is “5” and the number of CRC bits is “16”, the sum of the number of ACK, CRC, and identifier bits is the nearest multiple of 8 ( In this case, the number of bits of the identifier is determined to be “3” and the identifier is determined to be “100” so as to be “24”).

  Next, the number of identifier bits assigned to the command frame having the third highest communication frequency after the 12-bit ID data frame and the ACK frame is determined. That is, in the command frame, the number of bits indicating the command which is the control information is “5” and the number of bits of the CRC is “16”, so the sum of the bits of the command, CRC and identifier is the most recent multiple of 8 (this In this case, the number of bits of the identifier is determined to be “3”, and the identifier is determined to be “101”.

Further, in order to cope with future expansion of the communication system, which is not required in the current system, the number of identifier bits assigned to the data frame for expansion is determined as follows. Here, a case where the data frame for extension is a data frame having ID lengths of 4 bits, 16 bits, 24 bits, and 32 bits will be described.
In the 4-bit ID data frame, the number of bits in the remote is “1”, the number of bits in the size is “0”, and the number of bits in the ID is “4”. The number of bits of the identifier is determined to be “3” and the identifier is determined to be “110” so that becomes the latest multiple of 8 (in this case, “8”).

In the 16-bit ID data frame, the number of bits of the remote is “1”, the number of bits of the size is “2”, and the number of bits of the ID is “16”. The number of bits of the identifier is determined to be “5” and the identifier is determined to be “11100” so that becomes the latest multiple of 8 (in this case, “24”).
In the 24-bit ID data frame, the number of bits of the remote is “1”, the number of bits of the size is “2”, and the number of bits of the ID is “24”. The number of bits of the identifier is determined to be “5” and the identifier is determined to be “11101” so that becomes the latest multiple of 8 (in this case, “32”).

In the 32-bit ID data frame, the number of bits of the remote is “1”, the number of bits of the size is “2”, and the number of bits of the ID is “32”. The number of bits of the identifier is determined to be “5” and the identifier is determined to be “11110” so that the sum of the number and the number of bits of the ID becomes the most recent multiple of 8 (in this case, “40”). .
For burst frames having a plurality of data and a plurality of CRCs in the frame, unlike the above-described data frame, the identifier is set such that the sum of the number of bits of the identifier, remote, size, and ID is the most recent multiple of 8. The number of bits of the identifier is arbitrarily determined without determining the number of bits.

  In the 12-bit ID burst frame, the remote bit number is 1 bit, the size bit number is 4 bits, and the ID bit number is 12 bits, but the identifier bit number is determined to be 7 bits (for example, the sum of the bit numbers). Is determined to be “1111100”. In the 32-bit ID burst frame, the remote bit number is 1 bit, the size bit number is 8 bits, and the ID bit number is 32 bits. Is determined to be “1111101”. In a burst frame, a 16-bit CRC code (error detection unit) is added every 128 bits; 16 bytes (unit data portion).

  FIG. 7 shows a burst frame having a 12-bit ID, and the portion from the identifier at the beginning to the remote, size, and ID corresponds to the header. In this embodiment, the CRC code arranged following the header and the subsequent 16-byte unit data portion is generated by the CRC calculator 22 for the header and the unit data portion. (Control error detection code). Therefore, it is possible to detect a case where an error occurs in the header portion due to the CRC code.

  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 processing at the time of data transmission and the error detection processing at the time of data reception will be sequentially described with reference to FIGS.

(1) Error detection processing during data transmission The data communication device 1 performs error detection processing during data transmission shown in FIG. 8 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 the transmission data is not detected, it is determined that the transmission data is not normal (step S1: YES), 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 processing during data reception The data communication device 1 performs error detection processing during data reception shown in FIG. 9 when data is received. 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 strings shown in the 4B5B coding table If a bit string (undefined bit string) is detected, it is determined that 4B5B encoding is not normal (step S11: YES), and it is detected that a coding error has occurred (step S12).

  Next, the data communication apparatus 1 performs CRC error detection (code error detection) for determining whether or not the header and data included in the link layer frame are normal in the reception LLF decoder 20 (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 (step S13: YES), 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 (step S15: YES), 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 different from the normal sequence, the data communication apparatus 1 determines that the bit sequence of the link layer frame is not normal (step S17: YES), and detects that a state error has occurred. (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 (step S19: YES), 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. 10 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.

  Next, processing when a CRC error is detected in a part of the unit data portion when a burst frame is received will be described with reference to FIGS. As shown in FIG. 11A, when an error is detected by CRC2 for DATA2, which is the second unit data portion from the beginning, the receiving side requests retransmission of DATA2 from the transmitting side. FIG. 12 shows a retransmission processing sequence. (1) The transmitting side transmits a 12-bit ID burst frame, and (2) the receiving side receives the frame and returns an ACK frame. Then, the receiving side performs error checking using each CRC code, and when an error is detected for DATA2, (3) a frame requesting retransmission of DATA2 is transmitted to the transmitting side. When the transmission side receives the retransmission request frame, (4) retransmits the DATA2 portion, and (5) when the reception side receives the retransmitted data, it returns an ACK frame. Then, the receiving side performs error check again on the retransmitted DATA2.

  FIG. 11B shows a communication frame to be retransmitted by the transmission side in the above (4), in which DATA2 and CRC2 are added to the same header portion as in (a). The identifier in this case may be either the same burst transmission as in (a) or the retransmission of a part of data including the header. FIG. 11C shows a case where 128-bit DATA2 is divided into two communication frames of 64 bits and retransmitted twice.

As described above, according to the present embodiment, communication is performed using a communication frame including a header including a control code, a data portion including transmission data, and an error detection unit including a CRC code. Then, when the transmission side performs transmission by including a control error detection code for performing error detection on the header in the error detection unit, the reception side performs header error detection based on the control error detection code. Therefore, whether or not an error has occurred in the header can be detected based on the CRC code.
Further, the transmission side divides the data part into a plurality of unit data parts with a predetermined number of bits (for example, 16 bytes) as a unit, and an error detection part that performs error detection on the data part is divided into a plurality of unit data parts. A plurality are provided correspondingly. Then, the receiving side performs error detection for each of the plurality of unit data parts. Therefore, an error can be detected for each unit data portion in the burst transmission frame.

Further, since the transmission side generates the CRC code so that the error detection unit performs error detection in combination with the header and the first unit data part that follows, the increase in the number of bits of the error detection code can be suppressed. Further, since the same type of error detection code; CRC code is used for the control error detection code and the error detection code added for each of the plurality of unit data parts, the processing on the transmission side and the reception side is simplified.
In addition, the receiving side requests the transmitting side to retransmit the portion in which the error is detected by the CRC code, and the transmitting side retransmits the requested portion upon receiving the retransmission request. Therefore, even in the case of burst transmission with a long communication frame transmitted at a time, only the requested unit data part can be retransmitted, so that communication efficiency is improved.

  In addition, when the transmission side performs 4B5B encoding with the communication frame as a link layer frame, a preamble, a frame start unit, and a frame end unit are added to the 4B5B encoded link layer frame to generate a physical layer frame, and further, NRZI Bit error detection and form error detection are performed when transmitting to the communication channel after encoding. On the other hand, the receiving side performs coding error detection, error detection using a CRC code, form error detection, and state error detection for the received physical layer frame, and the transmission side performs timeout error detection. Therefore, the reliability of communication can be further improved by combining error detection using a CRC code with various other types of error detection.

(Second embodiment)
13 to 15 show a second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. The second embodiment shows a process of dynamically changing the number of bits of the CRC code in the error detection unit during the communication process. FIG. 13 conceptually shows the above processing. For example, in a communication environment where there is little disturbance and the number of error detections is small, the number of bits of the CRC code is set to 16 bits. When CRC errors are frequently detected, the number of bits of the CRC code is sequentially increased to 24 bits and 32 bits.

  FIG. 14 shows a processing sequence between the transmission side and the reception side, and FIG. 15 shows a configuration of the corresponding data communication apparatus 31. The data communication device 31 includes three CRC calculators 22A to 22C, and generates 16-bit, 24-bit, and 32-bit CRC codes, respectively. The CRC codes generated and output from the CRC calculators 22A to 22C are input to the selector 23, and input switching control of the selector 23 is performed by the transmission / reception sequencer 33.

  As shown in FIG. 14, the transmission side (1) first performs transmission using a CRC calculator 22A using a 16-bit CRC code. (2) The receiving side receives the transmitted frame, returns an ACK frame, performs error checking using the CRC code, and if an error is detected, (3) attaches a 24-bit CRC code to the transmitting side. A frame requesting retransmission of the received data is transmitted. When the transmission side receives the retransmission request frame, the transmission side switches to use the CRC computing unit 22B, and (4) retransmits the data with the 24-bit CRC code.

(5) When receiving the retransmitted data, the receiving side returns an ACK frame, and retransmits the error check using a 24-bit CRC code. When an error is detected, (6) this time, a frame requesting retransmission of data with a 32-bit CRC code is transmitted to the transmission side. Upon receiving the retransmission request frame, the transmission side switches to use the CRC calculator 22C, and (7) retransmits the data with the 32-bit CRC code. (8) When receiving the retransmitted data, the receiving side returns an ACK frame.
In the example shown in FIG. 14, when the CRC error is detected, an increase in the number of bits of the CRC code is requested immediately. However, of course, the present invention is not limited to this, and communication per a predetermined time in communication using the 16-bit CRC code is required. It is sufficient to request an increase in the number of bits when the CRC error detection frequency exceeds a predetermined threshold.

  As described above, according to the second embodiment, the receiving side requests the transmitting side to change the number of bits of the CRC code in accordance with the frequency of retransmission request, and the transmitting side makes an error in response to the request. Change the number of bits of the detection code. Therefore, the accuracy of error detection can be changed according to the communication environment.

The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.
As for the error detection code for control, a code may be created only for the control information part.
The state error detection means, timeout error detection means, bit error detection means, coding error detection means, and form error detection means may be provided as necessary.
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.
The present invention may be applied to a communication system in which the data frame having the highest communication frequency in the communication network is not a data frame having an ID length of 12 bits but a data frame having an ID length other than 12 bits.
The present invention may be applied to a communication system in which the frame with the second highest communication frequency is not an ACK frame but a command frame.

  In the drawings, 1 is a data communication device (transmitter, receiver), 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), and 16 is a 4B5B decoder ( Reference numeral 20 denotes a reception LLF decoder (form error detection means, code error detection means).

Claims (14)

In a data communication method for performing communication using a communication frame including a control information unit including at least a control code, a data unit including transmission data, and an error detection unit including an error detection code,
When the transmission side performs transmission by including a control error detection code for performing error detection on the control information unit in the error detection unit,
The data communication method characterized in that the receiving side performs error detection of the control information section based on the control error detection code. The transmission side divides the data part into a plurality of unit data parts with a predetermined number of bits as units, and an error detection unit that performs error detection on the data part corresponds to the plurality of unit data parts. Multiple
The data communication method according to claim 1, wherein the receiving side performs error detection for each of the plurality of unit data parts.   The transmission side generates the control error detection code in the error detection unit so as to perform error detection by combining the control information unit and the first unit data unit following the control information unit. Item 3. A data communication method according to Item 2.   4. The data communication method according to claim 2, wherein the same type of error detection code is used for the control error detection code and the error detection code added to each of the plurality of unit data parts. The receiving side requests the transmitting side to retransmit a portion in which an error is detected by the error detecting code,
5. The data communication method according to claim 2, wherein the transmission side retransmits the requested portion when receiving the retransmission request. 6. The receiving side requests the transmitting side to change the number of bits of the error detection code according to the frequency of the request for retransmission,
6. The data communication method according to claim 5, wherein the transmission side changes the number of bits of the error detection code in response to the request. The transmission side performs 4B5B encoding of the communication frame as a link layer frame,
A physical layer frame is generated by adding a preamble, a frame start portion and a frame end portion to the 4B5B encoded link layer frame,
The generated physical layer frame is encoded with NRZI (Non Return to Zero Inversion), and when the NRZI encoded physical layer frame is transmitted as a transmission frame to the communication path, it is determined whether or not the transmission data is normal. Bit error detection,
Perform form error detection to determine whether the configuration and content of the link layer frame is normal,
When the receiving side receives the physical layer frame, the receiving side performs coding error detection for determining whether or not 4B5B encoding is normal for the received physical layer frame,
Using the error detection code, performing error detection to determine whether the control information part and the data part included in the link layer frame are normal,
Perform form error detection to determine whether the configuration and content of the link layer frame is normal,
Performing a state error detection to determine whether the bit sequence of the link layer frame is normal,
The said transmission side performs the timeout error detection which determines whether the ACK (ACKnowledgement) frame was normally received within the predetermined time from the said receiving side, The one of Claim 1 thru | or 6 characterized by the above-mentioned. Data communication method. When the transmitter transmits a communication frame including a control information unit including at least a control code, a data unit including transmission data, and an error detection unit including an error detection code, and when a receiver receives the communication frame, In a data communication system that performs error detection in a communication frame using an error detection code,
The transmitter includes a control error detection code generation unit that generates a control error detection code for performing error detection on the control information unit, and transmits the error detection unit including the control error detection code. And
When the receiver receives the communication frame, the receiver performs error detection of the control information unit based on the control error detection code. The transmitter divides the data part into a plurality of unit data parts each having a predetermined number of bits, and an error detection unit that performs error detection on the data part corresponds to the plurality of unit data parts. Generate to provide multiple,
9. The data communication system according to claim 8, wherein the receiver performs error detection for each of the plurality of unit data parts.   The control error detection code generation unit generates the control error detection code so as to perform error detection by combining the control information unit and the first unit data unit following the control information unit. 9. The data communication system according to 9.   11. The data communication system according to claim 9, wherein the same type of error detection code is used for the control error detection code and the error detection code added to each of the plurality of unit data parts. The receiver requests the transmitter to retransmit a portion in which an error is detected by the error detection code,
12. The data communication system according to claim 9, wherein when the transmitter receives the retransmission request, the transmitter retransmits the requested portion. The receiver requests the transmitter to change the number of bits of the error detection code according to the frequency of the retransmission request,
13. The data communication system according to claim 12, wherein the transmitter changes the number of bits of the error detection code according to the request. The transmitter 4B5B encodes a link layer frame including data, generates a physical layer frame by adding a preamble, a frame start part, and a frame end part to the 4B5B encoded link layer frame. The physical layer frame is NRZI (Non Return to Zero Inversion) encoded, the NRZI encoded physical layer frame is transmitted as a transmission frame to the communication path,
Bit error detection means for performing bit error detection for determining whether transmission data 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;
Timeout error detection means for performing timeout error detection for determining whether or not an ACK (ACKnowledgement) frame is normally received within a predetermined time;
The receiver comprises 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 received frame from a communication path;
Code error detection means for determining whether or not the control information and data included in the link layer frame are normal using the error detection code;
Form error detection means for performing form error detection for determining whether the configuration and contents of the link layer frame are normal;
The data communication system according to any one of claims 8 to 13, further comprising state error detection means for performing state error detection for determining whether or not the arrangement of bit strings in the link layer frame is normal.

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