Subscriber station for serial bus system and communication method in serial bus system

Abstract

The present invention relates to a subscriber station (10; 30) for a serial bus system (1) and a method of communication in the serial bus system (1). The subscriber station (10; 30) comprises: a communication control device (11; 31) for controlling communication between the subscriber station (10; 30) and one or more other subscriber stations (10; 20; 30) of the bus system; The communication control device (11; 31) has a transmitting / receiving device (12; 32) configured to serially transmit a transmission signal (TXD) generated by the communication control device (11; 31) to a bus (40) of a bus system (1) and to serially receive a signal from the bus (40) of the bus system (1); the communication control device (11; 31) is configured to generate a transmission signal (TXD) according to a frame (450; 450_1; 450_2) and to insert two checksums (HCRC, FCRC) that calculate different bits of the frame (450; 450_1; 450_2) into the frame (450; 450_1; 450_2); and the communication control device (11; 31) is configured such that a reverse stuff bit is inserted into the bit stream of the frame (450; 450_1; 450_2) after five identical bits, thereby the frame (450; 450_1; 450_2) is configured to insert dynamic stuff bits, and the communication control device (11; 31) is configured to calculate the two checksums (HCRC, FCRC) in such a way that at most one of the two checksums (HCRC, FCRC) calculates the dynamic stuff bits together.

Description

Technology Field

[0001] The present invention relates to a subscriber station for a serial bus system; and a communication method in a serial bus system that operates with high data transmission speed, great flexibility, and great error robustness. Background Technology

[0002] For example, a bus system for communication between sensors and control units in a vehicle must be able to transmit large amounts of data depending on the technical system or various functions of the vehicle. In this case, data must be transmitted from the transmitter to the receiver faster than before, and often, large data packets must also be transmitted when necessary.

[0003] Currently, bus systems in which data is transmitted as messages under the ISO 11898-1:2015 standard, a CAN protocol specification utilizing CAN FD, are in the vehicle introduction phase. Messages are transmitted between bus subscriber stations of the bus system, such as sensors, control units, and encoders. In this first phase, CAN FD is used in vehicles by most manufacturers with a data bit rate of 2 Mbit / s and an arbitration bit rate of 500 kbit / s.

[0004] To achieve higher data transmission speeds, a successor bus system for CAN FD, hereinafter referred to as CAN XL, is currently under development. In addition to pure data transmission via the CAN bus, CAN XL must also support other functions such as Safety, Security, and Quality of Service (QoS). These are fundamental attributes required for autonomous vehicles.

[0005] It is highly desirable for CAN XL, CAN FD, and Classical CAN to be compatible. In this case, the res bit of the CAN FD frame is used to distinguish between CAN FD and CAN XL frames. Due to compatibility, the rules for dynamic stuff bits used in the CAN FD arbitration field also apply to CAN XL up to the res bit.

[0006] For the functional safety of the system, it is highly advantageous and important to keep the residual error probability as low as possible. Class 1 errors, namely incorrectly inverted and sampled bits (bit flips), and / or Class 2 errors, namely locally accumulated bit errors (burst errors), can be detected with sufficient probability using a checksum (CRC = Cyclic Redundancy Check). It should be noted that the receiving subscriber station also performs format checking of the frame. This is particularly helpful in detecting burst errors. The quality of error detection can be expressed through the residual error probability. The residual error probability indicates the probability that a frame will be accepted as correct despite errors at the receiving subscriber station (receiving node) of the bus system, rather than at the frame's transmitter.

[0007] In the case of Classical CAN, CRC calculation has the following disadvantages. In Classical CAN, dynamic stuff bits are not included in the CRC calculation. For this reason, Class 3 errors exist in Classical CAN, where the checksum (CRC) cannot be reliably detected. This error (Class 3) is caused by a transition of just two bits, also known as a bit flip. In this case, one bit flip creates a dynamic stuff condition, and the other bit flip cancels the dynamic stuff condition. At this point, the order of bit flips in the serially transmitted bits (bit stream) does not matter. Therefore, even though CRC calculation could reliably detect five bit flips (Class 1 error) in Classical CAN, there is a high probability that the calculation will fail to detect these errors. Consequently, Class 3 errors are particularly problematic or critical errors.

[0008] However, in the case of CAN FD, the CRC calculation has the following disadvantage. To make CAN FD robust against Class 3 errors, dynamic stuff bits are included in the CRC calculation. However, it was later discovered that there are Class 4 errors that are not detected by the CAN FD CRC. The aforementioned Class 4 error is a single bit drop or bit insertion into the data stream of the receiving subscriber station under dynamic stuff conditions. In other words, due to incorrect resynchronization, the receiving subscriber station sees one bit more or one bit less than what was actually transmitted from the transmitting subscriber station (transmitting node). However, this is not noticeable because CAN's dynamic stuff bits are inserted only after five identical bits of the same value.

[0009] In order for dynamic stuff bits to be included in the CRC calculation in CAN FD, a "stuff bit counter" is required in the CRC field. While the "stuff bit counter" reduces the probability that a Class 4 error will not be detected, it does not completely solve the problem. However, this "stuff bit counter" causes complexity and excess data (overhead), which reduces the transmittable user data rate.

[0010] In addition, CAN FD does not have a header checksum (Header CRC). As a result, code errors in the data length field (DLC = DataLengthCode) cannot be detected.

[0011] Therefore, due to a bit error within the code of the data length field, the receiving subscriber station (receiving node) of the bus system, rather than the transmitter of the CAN FD frame, may decode an incorrect frame length in the CAN FD frame. Consequently, the receiving subscriber station (receiving node) checks the checksum (CRC) at the wrong place.

[0012] If CRC calculation is performed in CAN XL as in CAN FD, CAN XL will have the same disadvantages as CAN FD. The problem to be solved

[0013] Therefore, the objective of the present invention is to provide a communication method for a serial bus system and a subscriber station for a serial bus system that solves the aforementioned problems. In particular, in order to achieve high error robustness of communication even at high data transmission speeds and when the amount of user data per frame increases, a communication method for a serial bus system and a serial bus system must be provided in which errors related to dynamic stuff bits within a bit stream are detected very reliably. means of solving the problem

[0014] The above problem is solved by a subscriber station for a serial bus system having the features of claim 1. The subscriber station has a communication control device for controlling communication between the subscriber station and one or more other subscriber stations of the bus system; and a transmitting / receiving device configured to serially transmit a transmission signal generated by the communication control device to a bus of the bus system and serially receive a signal from the bus of the bus system; wherein the communication control device is configured to generate a transmission signal according to a frame and to insert two checksums that calculate different bits of the frame into the frame; wherein the communication control device is configured to insert a dynamic stuff bit into the frame in such a manner that a reverse stuff bit is inserted into the bit stream of the frame after five identical bits; and wherein the communication control device is configured to calculate two checksums in such a manner that at most one of the two checksums calculates the dynamic stuff bit together.

[0015] The aforementioned subscriber station can sufficiently reliably detect Class 3 and Class 4 errors due to its configuration. This is because one of the two checksums (CRCs) of the CAN XL frame can sufficiently reliably detect Class 3 errors, and the other checksum (CRC) can sufficiently reliably detect Class 4 errors. Consequently, a "Stuff Bit Count" field can be stored within the frame, which increases the user data rate. As a result, for the aforementioned subscriber station, a "Stuff Bit Count" field, such as that in CAN FD, is not strictly necessary. Nevertheless, to further reduce the probability of residual errors, a "Stuff Bit Count" field, referred to here as the SBC field, can be added to the CAN XL frame.

[0016] In addition, the aforementioned subscriber station can very effectively avoid the two disadvantages of CAN FD mentioned in relation to stuff bits due to its configuration. In other words, the said subscriber station can sufficiently reliably detect errors when sampling the data length code. Through this, the frame receiver can know the exact frame length and, accordingly, check the checksum (CRC = Cyclic Redundancy Check) at the end of the frame at the correct point.

[0017] As a result, even if the amount of user data per frame increases in the subscriber country, frames can be transmitted and received functionally very safely with high flexibility and a low error rate in relation to current events during bus system operation.

[0018] In this case, the arbitration announced by CAN in the first communication stage can be maintained, particularly by the subscriber station within the bus system, and the transmission speed can be increased more significantly compared to CAN or CAN FD.

[0019] The method performed by the subscriber station may also be used when there are one or more CAN subscriber stations and / or one or more CAN FD subscriber stations within the bus system that transmit messages according to the CAN protocol and / or the CAN FD protocol.

[0020] Other desirable configurations of the subscriber country are specified in dependent claims.

[0021] According to one option, the communication control device is configured to insert a first field into a frame coded with a number of dynamic stuff bits, and the communication control device is configured to insert at least one first field before a data field into which user data of the frame is inserted.

[0022] A transmitting / receiving device for serially transmitting a transmission signal generated by a communication control device to a bus of a bus system may be configured such that, for a message exchanged between subscriber stations of a bus system, the bit time of a signal transmitted to the bus in a first communication stage may be different from the bit time of a signal transmitted in a second communication stage.

[0023] According to one particular configuration, a communication control device is configured to insert a second field into a frame, configured to check whether the bit stream of a frame is offset by at least one bit compared to an expected frame at a subscriber station of a bus system that has received the frame but has not transmitted it, and the communication control device is configured to insert at least one second field after a data field within the frame, in particular to insert at least one field after a frame checksum formed across all bits within the frame.

[0024] According to one embodiment, a communication control device is configured to insert a synchronization field having two bits in such a way that the two bits have different values ​​after at least one second field within a frame, and accordingly, the bits form a synchronization edge arranged to switch the bit rate for transmitting a transmission signal to a bus according to a bit pattern and / or to switch the physical layer of a transmitting / receiving device.

[0025] A frame formed for a message can be configured to be compatible with CAN FD, in which case, in the first communication stage, it is agreed which of the subscriber stations of the bus system obtains at least temporarily conflict-free exclusive access rights to the bus in the subsequent second communication stage.

[0026] The subscriber station described above may be part of a bus system comprising an additional bus and two or more subscriber stations connected to each other via the bus in a manner that communicates in series. In this case, at least one of the two or more subscriber stations is the subscriber station described above.

[0027] The aforementioned problem is also solved by a method of communication in a serial bus system according to claim 13. This method is implemented by a subscriber station of a bus system equipped with a communication control device and a transmitting / receiving device, and the method comprises the steps of: controlling communication between the subscriber station and one or more other subscriber stations of the bus system using the communication control device; transmitting a transmission signal generated by the communication control device to a bus of the bus system using the transmitting / receiving device; -the transmitting / receiving device is also configured to receive a signal serially from the bus of the bus system-; and generating a transmission signal according to a frame using the communication control device; -the communication control device is configured to insert two checksums into the frame that calculate different bits of the frame-; the communication control device inserts a dynamic stuff bit into the frame in such a way that a reverse stuff bit is inserted into the bit stream of the frame after five identical bits, and the communication control device calculates two checksums in such a way that at most one of the two checksums calculates the dynamic stuff bit together.

[0028] The present method provides the same advantages as previously mentioned in relation to the subscriber country.

[0029] Other possible embodiments of the present invention include unspecified combinations of features or embodiments described above or below in connection with the embodiments. In this case, a person skilled in the art would add individual aspects to each basic form of the present invention as improvements or additions. Brief explanation of the drawing

[0030] The present invention is described below in more detail with reference to the attached drawings and based on embodiments. FIG. 1 is a simplified block diagram of a bus system according to a first embodiment. FIG. 2 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to a first embodiment. FIG. 3 is a simplified schematic block diagram of a subscriber station of a bus system according to a first embodiment. FIG. 4 is a graph showing the time curves of bus signals (CAN-XL_H and CAN-XL_L) at a subscriber station according to the first embodiment. FIG. 5 is a graph showing the time curve of the differential voltage (VDIFF) of bus signals (CAN-XL_H and CAN-XL_L) at a subscriber station according to the first embodiment. FIG. 6 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to a second embodiment. FIG. 7 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to a third embodiment. FIG. 8 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to the fourth embodiment. FIG. 9 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to the fifth embodiment. FIG. 10 is a diagram for explaining the structure of a message that can be transmitted from a subscriber station of a bus system according to the 6th embodiment. Elements that are identical or functionally identical in the drawings are assigned the same reference numerals unless otherwise specified. Specific details for implementing the invention

[0031] FIG. 1 illustrates a bus system (1) configured, as described below, particularly for a CAN bus system, a CAN FD bus system, a CAN XL bus system and / or variations thereof. The bus system (1) can be used in vehicles, particularly in automobiles, airplanes, etc., or in hospitals, etc.

[0032] In FIG. 1, the bus system (1) comprises a plurality of subscriber stations (10, 20, 30) connected to a bus (40) each having a first bus core (41) and a second bus core (42). The bus cores (41, 42) may also be referred to as CAN_H and CAN_L or CAN-XL_H and CAN-XL_L and are used for electrical signal transmission after the combination of dominant levels for a signal or the generation of recessive levels or other levels in a transmission state. Messages (45, 46) can be transmitted serially between individual subscriber stations (10, 20, 30) in the form of signals through the bus (40). When communicating on the bus (40), if an error occurs, as illustrated by the black zigzag block arrow in FIG. 1, an error frame (47) (error flag) may optionally be transmitted. The subscriber countries (10, 20, 30) are, for example, control devices, sensors, display devices of automobiles.

[0033] As illustrated in FIG. 1, the subscriber station (10) includes a communication control device (11), a transmitting / receiving device (12), and a frame inspection module (15). The subscriber station (20) includes a communication control device (21) and a transmitting / receiving device (22). The subscriber station (30) includes a communication control device (31), a transmitting / receiving device (32), and a frame inspection module (35). The transmitting / receiving devices (12, 22, 32) of the subscriber stations (10, 20, 30) are each directly connected to a bus (40), although not illustrated in FIG. 1.

[0034] Each communication control device (11, 21, 31) is used to control communication through the bus (40) between each subscriber station (10, 20, 30) connected to the bus (40) and one or more other subscriber stations (10, 20, 30).

[0035] The communication control device (11, 31) creates and reads a first message (45), for example, a modified CAN message (45). In this case, the modified CAN message (45) is configured based on the CAN XL format, which is described in more detail with reference to FIG. 2 and in which each frame inspection module (15, 35) is used. Additionally, the communication control device (11, 31) may be configured to supply a CAN XL message (45) or a CAN FD message (46) to a transmitting / receiving device (32) or to receive from said transmitting / receiving device as needed. In this case as well, each frame inspection module (15, 35) is used. That is, the communication control device (11, 31) creates and reads the first message (45) or the second message (46), and the first and second messages (45, 46) are distinguished by their data transmission standards, in short, in this case, either CAN XL or CAN FD.

[0036] The communication control unit (21) can be configured like a conventional CAN controller according to ISO 11898-1:2015, that is, like a CAN FD tolerant Classical CAN controller or a CAN FD controller. The communication control unit (21) creates and reads a second message (46), such as a CAN FD message (46). In the case of a CAN FD message (46), it may contain 0 to 64 data bytes and is also transmitted at a much faster data transmission rate than when transmitting Classical CAN messages. In particular, the communication control unit (21) is configured like a conventional CAN FD controller.

[0037] The transmitting / receiving device (22) may be configured like a conventional CAN transceiver or CAN FD transceiver according to ISO 11898-1:2015. The transmitting / receiving device (12, 32) may be configured to supply a message (45) in the CAN XL format or a message (46) in the current CAN FD format for a related communication control device (11, 31) as needed, or to receive from said communication control device.

[0038] The formation and subsequent transmission of a message (45) having a CAN XL format and the reception of said message (45) can be implemented by two subscriber stations (10, 30).

[0039] FIG. 2 illustrates a CAN XL frame (450) supplied by a communication control unit (11) for a transmitting / receiving device (12) for transmission to a bus (40) for a message (45). In this case, the communication control unit (11) creates a frame (450) that is compatible with CAN FD in this embodiment, as also illustrated in FIG. 2. This applies similarly to the communication control unit (31) and the transmitting / receiving device (32) of the subscriber station (30).

[0040] According to FIG. 2, a CAN XL frame (450) is divided into different communication phases (451, 452) for CAN communication on the bus (40), namely an arbitration phase (451) and a data phase (452). The frame (450) has an arbitration field (453), a control field (454), a data field (455), a checksum field (456) for a checksum (FCRC), and a transition sequence (ADS) and acknowledgment field (457).

[0041] In the arbitration stage (451), in bits, between the subscriber stations (10, 20, 30) by identifier (ID) within the arbitration field (453), it is agreed which subscriber station (10, 20, 30) intends to transmit a message (45, 46) having the highest priority and thereby obtain exclusive access rights to the bus (40) of the bus system (1) during the next transmission time in the subsequent data stage (452). In the arbitration stage (451), a physical layer such as that in CAN and CAN FD is used. The physical layer corresponds to the bit transmission layer or layer (1) of the known OSI model (Open Systems Interconnection Model).

[0042] The focus during step (451) is that a known CSMA / CR method is used to allow simultaneous access of subscriber stations (10, 20, 30) to the bus (40) without the higher priority messages (45, 46) being destroyed. In this way, additional bus subscriber stations (10, 20, 30) can be added to the bus system (1) relatively simply, which is highly desirable.

[0043] As a result of the CSMA / CR method, there must exist a so-called recessive state on the bus (40) that can be overwritten by other subscriber stations (10, 20, 30) having a dominant state on the bus (40). In the recessive state, high impedance conditions prevail at individual subscriber stations (10, 20, 30), which combine with parasitic components of the bus circuit to cause a longer time constant. Consequently, when applied to actual vehicles, the maximum bit rate of the CAN FD physical layer today is currently limited to about 2 megabits per second.

[0044] In the data stage (452), in addition to a part of the control field (454), user data of a message (45) from a CAN XL frame or data field (455); a checksum field (456) for a checksum (FCRC); and a field (DAS) used for transitioning from the data stage (452) to the arbitration stage (451) are transmitted.

[0045] The transmitter of the message (45) begins transmitting bits of the data stage (452) to the bus (40) only when the subscriber station (10) succeeds in arbitration as a transmitter and thereby has exclusive access rights to the bus (40) of the bus system (1) to transmit as a transmitter.

[0046] Very generally, in bus systems including CAN XL, the following different properties can be implemented compared to CAN or CAN FD:

[0047] a) The frame structure, including the proven attributes responsible for the robustness and user-friendliness of CAN and CAN FD, particularly identifiers and arbitration according to the CSMA / CR method, is taken over and, if necessary, adjusted.

[0048] b) The net data rate increased, in particular, to about 10 megabits per second.

[0049] c) The size of user data per frame is increased to approximately 4 kbytes or any other value.

[0050] As illustrated in FIG. 2, the subscriber station (10) uses a format according to ISO11898-1:2015, known by CAN / CAN FD, in part, specifically up to the FDF bit (including therein) in the arbitration stage (451) as the first communication stage. In contrast, the subscriber station (10) uses the CAN XL format described below from the FDF bit in the first communication stage and in the second communication stage, i.e., the data stage (452).

[0051] In this embodiment, CAN XL and CAN FD are compatible. In this case, the res bit (hereinafter referred to as the XLF bit) known by CAN FD is used to convert from the CAN FD format to the CAN XL format. Therefore, the frame formats of CAN FD and CAN XL are identical up to the res bit. The receiver detects, for the first time at the res bit, which format the frame will be transmitted in. A CAN XL subscriber station, i.e., subscriber station "10, 30" here, also supports CAN FD.

[0052] As an alternative to the frame (450) illustrated in FIG. 2 in which an 11-bit identifier is used, a CAN XL extended frame format in which a 29-bit identifier is optionally used is possible. This is identical to the CAN FD extended frame format known from ISO11898-1:2015 up to the FDF bit.

[0053] According to FIG. 2, the frame (450) is identical to the CAN FD base frame format according to ISO11898-1:2015 from the SOF bit to the FDF bit (including therein). Therefore, known structures are not further described here. Bits indicated by bold dash symbols on the bottom line of FIG. 2 are transmitted as dominant or '0' in the frame (450). Bits indicated by bold dash symbols on the top line of FIG. 2 are transmitted as recessive or '1' in the frame (450). In the CAN XL data stage (452), symmetrical '1' and '0' levels are used instead of recessive and dominant levels.

[0054] Generally, two different stuffing rules are applied when creating a frame (450). Up to the XLF bit of the control field (454), the dynamic bit stuffing rule of CAN FD is applied, so that a reverse stuff bit must be inserted consecutively after five identical bits. These stuff bits are also called dynamic stuff bits. After the resXL bit in the control field (454), the fixed stuffing rule is applied, so that a single fixed stuff bit must be inserted after a fixed number of bits. Alternatively, instead of a single stuff bit, two or more bits may be inserted as fixed stuff bits, which will be explained in more detail later.

[0055] In the frame (450), an XLF bit follows immediately after the FDF bit, which corresponds to the "res bit" of the CAN FD base frame format mentioned earlier. When the XLF bit is transmitted as 1, i.e., recessively, the frame (450) is identified as a CAN XL frame. In the case of a CAN FD frame, the communication control device (11) sets the XLF bit as 0, i.e., dominant.

[0056] In the frame (450), the resXL bit follows the XLF bit, which is a dominant bit for future use. The resXL bit must be transmitted as 0 for the frame (450), that is, as dominant. However, if the subscriber station (10) receives the resXL bit as 1, that is, as recessive, the receiving subscriber station (10) enters a Protocol Exception State, for example, as in the case of the CAN FD message (46) when res=1. Alternatively, the resXL bit may be defined in reverse, that is, it must be transmitted as 1, that is, as recessive. In this case, the receiving subscriber station enters a Protocol Exception State when the resXL bit is dominant.

[0057] In the frame (450), following the resXL bit, an Arbitration Data Switch (ADS) sequence is followed by a predetermined bit sequence coded. This bit sequence enables a simple and certain transition from the bit rate of the arbitration stage (451) (arbitration bit rate) to the bit rate of the data stage (452) (data bit rate). For example, the bit sequence of the ADS sequence consists of, in particular, an AL1 bit transmitted predominantly, that is, as 0. The AL1 bit is the last bit of the arbitration stage (451). In other words, the AL1 bit is the last bit before transitioning to the data stage (452), which has short bits. Within the AL1 bit, the physical layer of the transmitting / receiving device (12, 22, 32) is switched. The AL1 bit may also have a value of 1, depending on which value (0 or 1) is more suitable for switching the physical layer in the transmitting / receiving device (12, 32) (transceiver). The two subsequent bits DH1 and DL1 are already transmitted at the data bit rate. Therefore, in CAN XL, the DH1 and DL1 bits are time-short bits of the data phase (452).

[0058] In the frame (450), following the ADS sequence, a PT field is followed that identifies the contents of the data field (455). The contents indicate what type of information is contained in the data field (455). For example, the PT field indicates whether an "Internet Protocol (IP) frame exists in the data field (455) or whether a tunneled Ethernet frame exists, etc.

[0059] Following the PT field is a DLC field containing a Data Length Code (DLC) that indicates the number of bytes of the data field (455) of the frame (450). The Data Length Code (DLC) can take any value from 0 up to the maximum length of the data field (455) or the data field length. In particular, if the maximum data field length is 2048 bits, the Data Length Code (DLC) requires 11 bits, assuming that "DLC = 0" means a data field length with 1 byte and "DLC = 2047" means a data field length with 2048 bytes. Alternatively, a data field (455) with a length of 0 may be allowed, as in CAN, for example. In this case, DLC = 0 will code a data field length of, for example, 0 bytes. In this case, for example, the maximum data field length that can be coded in 11 bits is (2^11)-1 = 2047.

[0060] In the embodiment of FIG. 2, the SBC field follows the DLC field in the frame (450). The abbreviation SBC stands for "Stuff Bit Count". The SBC field codes the number of dynamic stuff bits within the header of the frame (450). In principle, the SBC field can be placed at any location in the header of the frame (450) between the ADS field and the end of the header of the frame (450). It is advantageous to place the SBC field before the header checksum (HCRC) so that the SBC field can be protected by the header checksum (HCRC).

[0061] In the frame (450) of FIG. 2, the header checksum (HCRC) follows the SBC field. The header checksum (HCRC) is a checksum for protecting the header of the frame (450), that is, all relevant bits from the beginning of the frame (450) by the SOF bit to the beginning of the header checksum (HCRC) {including all dynamic stuff bits and optionally fixed stuff bits up to the beginning of the header checksum (HCRC)}. The relevant bits include only the bits of the frame header that have variable values. In other words, the relevant bits do not include bits that always have a fixed value in the frame (450). That is, these bits with unchangeable values ​​are not protected because they have a fixed value. The length of the header checksum (HCRC) and, together with it, the length of the checksum polynomial according to the Cyclic Redundancy Check (CRC) must be selected to correspond to the desired Hamming distance. The data word to be protected by the header checksum (HCRC) is longer than 27 bits for the 11-bit data length code (DLC). Therefore, to achieve a Hamming distance of 6, the polynomial length of the header checksum (HCRC) must be at least 13 bits.

[0062] In the frame (450), a data field (455) follows the header checksum (HCRC). The data field (455) consists of 1 to n data bytes, where n is, for example, 2048 bytes or 4096 bytes or any other value. Alternatively, a data field length of 0 may be considered. The length of the data field (455) is coded in the DLC field as described above.

[0063] In a frame (450), a frame checksum (FCRC) follows the data field (455). The frame checksum (FCRC) consists of bits of the frame checksum (FCRC). The length of the frame checksum (FCRC) and, together with it, the length of the CRC polynomial should be selected to correspond to the desired Hamming distance. The frame checksum (FCRC) protects the entire frame (450). Alternatively, only the data field (455) is optionally protected by the frame checksum (FCRC).

[0064] In the frame (450), following the frame checksum (FCRC), a Data Arbitration Switch (DAS) sequence is followed by a predetermined bit sequence. This bit sequence enables a simple and reliable transition from the data bit rate of the data phase (452) to the arbitration bit rate of the arbitration phase (451). For example, the bit sequence begins with data bits (DH2, DH3) transmitted as 1 and data bits (DL2, DL3) transmitted as 0, as shown in FIG. 2. These are the last four bits of the data phase (452). Thus, the DL3 bit is the last bit before transitioning to the arbitration phase (451), which has the short bits, i.e., the long bits. These bits are followed by the AH1 bit of the arbitration phase (451), which has a value of 1. Within the AH1 bit, the physical layer of the transmitting / receiving device (12, 32) (transceiver) is switched. The AH1 bit may optionally have a value of 0, depending on which value (0 or 1) is more suitable for switching the physical layer in the transmitting / receiving device (12, 32) (transceiver). The RX subscriber station (10, 30), which is merely a receiver of the frame (450) and, i.e., does not transmit the received frame (450), uses the bit sequence (DH2, DH3, DL2, DL3) not only for synchronization but also as a format check pattern. Using this bit sequence, the RX subscriber station (10, 30) can detect whether the bit stream received from the bus (40) is sampled with an offset of, for example, 1 bit or 2 bits. According to another embodiment, the DAS field has three bits, namely the DH2 bit, the DL2 bit, and the AH1 bit. The first and last bits of the bits are transmitted as 1, and the middle bit as 0.

[0065] In the embodiments described above, at the edge between the DH3 bit and the DL2 bit or between the DH2 bit and the DL2 bit at the receiving subscriber station, the last synchronization before the transition from the data stage (452) to the arbitration stage (451) may be performed.

[0066] Accordingly, in the present embodiment, the DAS sequence includes a Format Check Pattern (FCP) that enables a subscriber station (10, 30), particularly its frame check module (15, 35), to detect an offset of the bit stream within the received frame (450), even if the relevant subscriber station (10, 30) is a receiver rather than a transmitter of the frame (450). In this case, the longer the bit pattern of the FCP field, the greater or stronger the shift that can be detected at the receiving subscriber station (10, 30). The bit pattern most advantageous for shift detection includes an even number (M) of bits, in which case the first M / 2 bits contain 1 and the next M / 2 bits contain 0. In the example of FIG. 2 with a 4-bit FCP field, the first two bits are transmitted as recessive (1). The last two bits of the FCP field are transmitted as dominant (0). Therefore, the 4-bit FCP field according to Fig. 2 differs from the general 2 bits at the beginning of the FCP field due to additional bits (DH3, DL3). However, the edge from recessive to dominant in the FCP field of Fig. 2 can perform the same function as in the DAS field without the DH3 and DL3 bits.

[0067] Very generally, the first M / 2 bits of the FCP field may contain 0 and the next M / 2 bits may contain 1. An offset of M-1 can be detected by the FCP field. This is described in more detail below in relation to FIG. 3.

[0068] In the frame (450), the DAS sequence is followed by an acknowledgment field (457) that begins as an RP field. The RP field contains a Sync Pattern that allows the receiving subscriber station (10, 30) to detect the start of the arbitration phase (451) after the data phase (452). The Sync Pattern enables the receiving subscriber station (10, 30), which does not know the exact length of the data field (455) due to, for example, an incorrect header checksum (HCRC), to be synchronized. Subsequently, these subscriber stations may transmit a "Negative Acknowledge" to report an incorrect reception. This is particularly important when CAN XL does not allow error frames (47) (Error Flags) in the data field (455).

[0069] In the ACK field (457), following the RP field, a plurality of bits for acknowledging or denying the correct reception of the frame (450) follow. In the example of FIG. 2, an ACK bit, an ACK dlm bit, a NACK bit, and a NACK dlm bit are provided. The NACK bit and the NACK dlm bit are optional bits. If the receiving subscriber station (10, 30) correctly receives the frame (450), these receiving subscriber stations transmit the ACK bit as the dominant bit. The transmitting subscriber station transmits the ACK bit as the recessive bit. Thus, the bits transmitted to the bus (40) in the form of the original frame (450) can be overwritten by the receiving subscriber station (10, 30). The ACK dlm bit is transmitted as a recessive bit used for separation from other fields. The NACK bit and NACK dlm bit are used to enable the receiving subscriber station to signal incorrect reception of the frame (450) through the bus (40). The function of these bits is the same as the function of the ACK bit and ACK dlm bit.

[0070] In the frame (450), the acknowledgment field (ACK field) (457) is followed by an end of frame field (EOF). The bit sequence of the end of frame field (EOF) is used to identify the end of the frame (450). The end of frame field (EOF) causes eight recessive bits to be transmitted at the end of the frame (450). This is a bit sequence that cannot occur within the frame (450). Thus, the end of the frame (450) can be reliably detected by the subscriber station (10, 20, 30).

[0071] The length of the EOF field varies depending on whether the dominant bit or the recessive bit is acknowledged in the NACK bit. If the transmitting subscriber station receives the NACK bit as dominant, the EOF field has 7 recessive bits. In other cases, the EOF field is only 5 recessive bits long.

[0072] In the frame (450), following the exit field (EOF), there is an inter-frame space (IFS = Inter Frame Space) not shown in FIG. 2. This inter-frame space (IFS) is configured like a CAN FD according to ISO11898-1:2015.

[0073] FIG. 3 illustrates the basic configuration of a subscriber station (10), comprising a communication control device (11), a transmitting / receiving device (12), and a frame inspection module (15) which is part of the communication control device (11). The subscriber station (30) is configured in a manner similar to that shown in FIG. 3, but the frame inspection module (35) is positioned separately from the communication control device (31) and the transmitting / receiving device (32) according to FIG. 1. Therefore, the subscriber station (30) is not described separately.

[0074] According to FIG. 3, the subscriber station (10) has, in addition to the communication control device (11) and the transmitting / receiving device (12), a microcontroller (13) to which the communication control device (11) is assigned; and alternatively, a system ASIC (16) (ASIC = Application-Specific Integrated Circuit) which may be a system basis chip (SBC) in which a plurality of functions required for the electronic module of the subscriber station (10) are integrated. Within the system ASIC (16), in addition to the transmitting / receiving device (12), an energy supply device (17) that supplies electrical energy to the transmitting / receiving device (12) is embedded. The energy supply device (17) typically supplies a voltage (CAN_Supply) of 5V. However, if necessary, the energy supply device (17) may supply a different voltage having a different value. In addition to, or alternatively, the energy supply device (17) may be configured as a current source.

[0075] The frame inspection module (15) has an insertion block (151) and an evaluation block (152) which will be described in more detail later.

[0076] Additionally, the transmitting / receiving device (12) has a transmitting module (121) and a receiving module (122). Although always referred to as the transmitting / receiving device (12) below, the receiving module (122) may optionally be provided in a separate device outside the transmitting module (121). The transmitting module (121) and the receiving module (122) may be configured as in a conventional transmitting / receiving device (22). The transmitting module (121) may specifically have at least one operational amplifier and / or one transistor. The receiving module (122) may specifically have at least one operational amplifier and / or one transistor.

[0077] The transmitting / receiving device (12) is connected to the bus (40), more precisely, to the first bus core (41) of the bus for CAN_H or CAN-XL_H and the second bus core (42) of the bus for CAN_L or CAN-XL_L. Voltage supply for an energy supply device (17) for supplying electrical energy, specifically voltage (CAN_Supply), to the first and second bus cores (41, 42) is performed through one or more terminals (43). Connection to ground or CAN_GND is implemented through terminal (44). The first and second bus cores (41, 42) are terminated by a terminating resistor (49).

[0078] The first and second bus cores (41, 42) are connected to a transmitting module (121), also referred to as a transmitter, and a receiving module (122), also referred to as a receiver, in the transmitting / receiving device (12), but the connection is not shown in FIG. 3 for simplification.

[0079] During the operation of the bus system (1), the transmission module (121) converts the transmission signal (TXD or TxD) of the communication control device (11) into a corresponding signal (CAN-XL_H and CAN-XL_L) for the bus core (41, 42) and transmits these signals (CAN-XL_H and CAN-XL_L) to the terminals for CAN_H and CAN_L on the bus (40).

[0080] The receiving module (122) generates a receiving signal (RXD or RxD) based on signals (CAN-XL_H and CAN-XL_L) according to FIG. 4 received from the bus (40), and transmits the receiving signal to the communication control device (11) as shown in FIG. 3. Except in an idle state or standby state, the transmitting / receiving device (12) always stops the transmission of data or messages (45, 46) on the bus (40) in normal mode using the receiving module (122), more precisely, regardless of whether the transmitting / receiving device (12) is the transmitter of the message (45).

[0081] According to the example of FIG. 4, the signals (CAN-XL_H and CAN-XL_L) have dominant and recessive bus levels (401, 402) as known by CAN, at least in the arbitration stage (451). On the bus (40), a differential signal (VDIFF = CAN-XL_H - CAN-XL_L) as shown in FIG. 5 is generated. Individual bits of the signal (VDIFF) having a bit time (t_bt) can be detected by a reception threshold of 0.7V. In the data stage (452), the bits of the signals (CAN-XL_H and CAN-XL_L) are transmitted faster than in the arbitration stage (451), i.e., with a shorter bit time (t_bt). Thus, in the data stage (452), the signals (CAN-XL_H and CAN-XL_L) are distinguished from the conventional signals (CAN_H and CAN_L) at least at a relatively higher bit rate.

[0082] The sequence of states (401, 402) for the signals (CAN-XL_H, CAN-XL_L) in FIG. 4 and the resulting curve of the voltage (VDIFF) in FIG. 5 are used only to explain the function of the subscriber station (10). The sequence of data states for the bus states (401, 402) can be selected as needed.

[0083] In other words, the transmitting module (121) generates a first data state as a bus state (402) having different bus levels for two bus cores (41, 42) of the bus line of the bus (40) according to FIG. 4 in a first operating mode; and a second data state as a bus state (401) having the same bus level for two bus cores (41, 42) of the bus line of the bus (40).

[0084] Additionally, the transmitting module (121) transmits bits to the bus (40) at a relatively higher bit rate for the time curves of the signals (CAN-XL_H, CAN-XL_L) in a second operating mode including a data phase (452). The CAN-XL_H and CAN-XL_L signals may be generated by a physical layer different from that of CAN FD in the data phase (452). In this way, the bit rate in the data phase (452) may be much higher than that of CAN FD.

[0085] The frame inspection module (15) of FIG. 3, in particular its insertion block (151), serves to insert an SBC field into the frame (450) when the subscriber station (10) acts as the transmitter of the frame (450). In this embodiment, the frame inspection module (15) of FIG. 3 is configured such that the SBC field has three bits, namely Bit0, Bit1, and Bit2. In this way, the SBC field generates as little excess data (data overhead) as possible. In the SBC field, the frame inspection module (15) inputs the number of dynamic stuff bits into bits Bit0 and Bit1, and inputs the parity of the first two bits into Bit2.

[0086] In this embodiment, the insertion block (151) inserts the SBC field in front of the header checksum (HCRC) in the frame (450). The frame inspection module (15), in particular the evaluation block (152), also uses the SBC field and all dynamic stuff bits of the frame header when generating the header checksum (HCRC). As a result, Class 3 and Class 4 errors can be detected.

[0087] The frame inspection module (15) of FIG. 3, in particular its evaluation block (152), is used for generating and inspecting header checksums and frame checksums, as well as for inspecting the number of dynamic stuff bits.

[0088] The evaluation block (152) of the receiving subscriber station can detect a deviation from the actual number in the frame header, i.e., an error, by comparing the number of received dynamic stuff bits in the frame header with the value of the SBC field.

[0089] In contrast, the evaluation block (152) excludes dynamic stuff bits when generating the frame checksum (FCRC). However, the evaluation block (152) includes other bits of the frame header, such as ID bits and RRS bits, into the frame checksum (FCRC). That is, these bits are double-protected. As a result, using the frame inspection module (15), particularly its evaluation block (152), Class 3 and Class 4 errors occurring in relation to dynamic stuff bits can be detected with a very high probability.

[0090] Thus, the receiving subscriber station (receiving node) (10), in particular its frame inspection module (15) and more precisely its evaluation block (152), can detect critical errors that may occur due to dynamic stuff bits within the received bit stream. The evaluation block (152) sends a corresponding message to the communication control unit (11). In this way, the received frame (450) can be discarded if it has an error. As a result, the communication control unit (11) can optionally transmit the error frame (47) to the bus (40).

[0091] However, using a "stuff count" field such as the SBC field reduces the probability of residual error. As a result, the probability that an invalid frame (450) is accepted as valid is much lower.

[0092] Therefore, the use of the SBC field ("Stuff Counts" field), which codes the number of dynamic stuff bits within the transmitted frame, is optional.

[0093] Where compatibility with CAN FD is not required, so-called fixed stuff bits (always present stuff bits) may be used in frames instead of dynamic stuff bits. Without dynamic stuff bits, Class 3 and Class 4 errors cannot occur. Additionally, "stuff count" fields, such as the SBC field, may be omitted. As a result, the number of bits to be transmitted is reduced, and even complexity is lowered.

[0094] According to a first variation of the first embodiment, the frame inspection module (15), particularly the evaluation block (152), is configured to exclude dynamic stuff bits when generating the header checksum (HCRC). In contrast, the frame inspection module (15), particularly the evaluation block (152), uses dynamic stuff bits when generating the frame checksum (FCRC). In this case, the frame inspection module (15), particularly the evaluation block (152), re-includes other bits of the frame header, such as ID bits, RRS bits, etc., into the frame checksum (FCRC). In this way, special Class 3 and Class 4 errors can be detected with sufficient certainty. This detection can be reported together with the error frame (47) when the error frame (47) is used.

[0095] According to a second variation of the first embodiment, the frame inspection module (15), particularly the evaluation block (152), is configured so as not to include dynamic stuff bits in either the checksum (HCRC, FCRC). In this way, Class 3 and Class 4 errors can be detected with sufficient certainty. This is because dynamic stuff bits can occur only from the SOF bit to the FDF bit. Up to three dynamic stuff bits can be included in this small area. Consequently, the length of burst errors (packet errors) that can be generated from Class 3 errors and are block-unit disturbances of the bit stream is limited. Consequently, the probability that the header (CRC) can detect said burst errors is increased. This detection can be reported together with the error frame (47) when the error frame (47) is used.

[0096] FIG. 6 illustrates a frame (450_1) according to a second embodiment in which CAN XL and CAN FD are compatible. In this embodiment, an error frame (error flag) (47) is used to signal an error.

[0097] In this embodiment, the frame (450_1) and the CAN XL frame format together are different from the frame (450) of FIG. 2 as described below. Below, only the differences from the frame (450) of FIG. 2 will be explained. Other than that, the frames (450, 450_1) of the two embodiments are identical.

[0098] In the frame (450_1), instead of the RP field, there is a SYN field of a fixed length of 2 bits. The SYN field includes a first bit (AL2) having a digital value of 0. A bit sequence of bits (AL2, AH1) together with a preceding bit (AH1) having a digital value of 1 provides a synchronization edge after a switch of the bit rate and physical layer (i.e., the mode of the CAN XL transceiver).

[0099] Therefore, there are two synchronization edges required for the robust function of CAN XL, namely, a synchronization edge immediately before the bit rate switch (DH3 => DL2) and a synchronization edge immediately after the bit rate switch (AH1 => AL2). In this way, it is possible to safely transition to the arbitration stage (451) before the data stage (452).

[0100] The value of the SYNdlm bit, the second bit of the SYN field, is 1. This is used to distinguish it from the ACK bit. If there is no error, the ACK bit is transmitted as 0 (dominant) by the receiving node, and an additional synchronization edge is generated accordingly.

[0101] Since errors can be signaled in advance by the error flag (47) as the error frame (error flag) (47) is used, the use of the NACK field is purely optional.

[0102] FIG. 7 illustrates a frame (450_2) according to a third embodiment in which CAN XL and CAN FD are compatible. In this embodiment, an error frame (error flag) (47) is used to signal an error.

[0103] In this embodiment, the frame (450_2) and the CAN XL frame format together are different from the frame (450_1) of FIG. 6 as described below. Below, only the differences from the frame (450_1) of FIG. 6 will be explained. Other than that, the frames (450_1, 450_2) of the two embodiments are identical.

[0104] There is no RP field or SYN field in the frame (450_2). Therefore, the synchronization required after the bit rate switch is performed at the edge "AH1(1) => ACK(0)". This solution has two advantages.

[0105] The first advantage is that the phase error immediately before synchronization for edge "AH1(1) => ACK(0)" in frame (450_2) of FIG. 7 is equal to or smaller than the phase error immediately before synchronization for edge "SYNdlm(1) => ACK(0)" in frame (450_1) of FIG. 6. This is because in frame (450_2) of FIG. 7, only two short bits (DL2, DL3) and one long bit (AH1) have passed since the last synchronization. In contrast, in frame (450_1) of FIG. 6, two long bits (AL2, SYNdlm) have passed.

[0106] The second advantage is that the overhead of the frame in Fig. 7 (450_2) is smaller than that of the frame in Fig. 6 (450_1). The frame in Fig. 7 (450_2) has two fewer long bits than the frame in Fig. 6 (450_1). As a result, the overhead is smaller and the net data transmission speed is faster.

[0107] In this embodiment as well, since the error flag (47) is used, the error can be signaled in advance by the error flag (47), so the use of the NACK field is purely optional.

[0108] FIG. 8 illustrates a frame (4500) according to a fourth embodiment of the present invention, in which the frame formats of CAN XL and CAN FD are incompatible. In this embodiment, the frame (4500) and the CAN XL frame format are different from the frame (450) of FIG. 2 as described below. Below, only the differences from the frame (450) of FIG. 2 will be explained. Other than that, the frames (450, 4500) of the two embodiments are identical.

[0109] Generally, when generating a frame (4500) according to the present embodiment, only a fixed stuffing rule is used, so a single fixed stuff bit must be inserted after a fixed number of bits. Alternatively, instead of a single stuff bit, two or more bits may also be inserted as fixed stuff bits. This leads to a fixed frame length or a fixed length of the frame (4500) when the value of the data length code (DLC) is known. This prevents various problems caused by dynamic stuff bits. As a result, an SBC field is unnecessary in the header of the frame (4500).

[0110] In the frame (4500) according to the present embodiment, the identifier (ID) is no longer limited to 11 bits or 29 bits, as in CAN FD. The number of bits (k) of the identifier (ID) can be freely selected. Alternatively, the number (k) may be set to a fixed value. For high-speed net data transmission rates, an ID of k = 8 bits is suitable. This is sufficient to grant a sufficient number of bus access priorities to each subscriber station (10, 20, 30) of the bus system (1). Of course, other values ​​for k may be selected as needed and depending on the number of various priorities in the bus system (1).

[0111] The RRS, IDE, FDF, and XLF bits of the frame (450) of Fig. 2 are no longer needed and are omitted in the frame (4500). This saves 4 bits, and as a result, frame overhead is reduced. This increases the net data transmission speed in the bus system (1).

[0112] The EOF field of the frame (4500) has a number of 5 bits only when the NACK bit is still dominant. In contrast, when the NACK bit is recessive, the EOF field has a number of 3 bits. This causes 6 recessive bits to be transmitted at the end of the frame (4500). This number of recessive bits cannot occur at other locations within the valid frame (4500) when a fixed stuff bit is inserted after 5 identical bits in the arbitration step (451). Alternatively, it may be 6 bits or more. In particular, the number of EOF bits must be adjusted to the number of bits followed by a fixed stuff bit.

[0113] In a frame (4500), the inter-frame interval (IFS) does not require a minimum length. In particular, the inter-frame interval (IFS) may have a length of 0. In this case, two frames (4500) are transmitted consecutively without interruption. However, to increase the robustness of the bus system (1) compared to the previously mentioned case, an inter-frame interval (IFS) having, for example, 1 bit is also useful. Currently, new subscriber stations on the bus (40) can be synchronized more reliably by the 7 recessive bits between the two frames (4500).

[0114] FIG. 9 illustrates a frame (4500_1) according to a fifth embodiment of the present invention in which the frame formats of CAN XL and CAN FD are incompatible. In this embodiment, the frame (4500_1) and, together with it, the CAN XL frame format are different from the frame (4500) of FIG. 8 as described in relation to the second embodiment.

[0115] Accordingly, within the frame (4500_1), there exists a SYN field having a fixed length of 2 bits instead of an RP field. As a result, synchronization is performed after the data step (452) as described in relation to the second embodiment.

[0116] Other than that, the frames (4500, 4500_1) of the two embodiments are identical.

[0117] FIG. 10 illustrates a frame (4500_2) according to the sixth embodiment of the present invention, in which the frame formats of CAN XL and CAN FD are incompatible. In this embodiment, the frame (4500_2) and, together with it, the CAN XL frame format are different from the frame (4500) of FIG. 8 as described in relation to the third embodiment.

[0118] Therefore, neither the RP field nor the SYN field exists within the frame (4500_2). As a result, synchronization is performed after the data step (452) as described in relation to the third embodiment.

[0119] Other than that, the frames (4500, 4500_2) of the two embodiments are identical.

[0120] All the aforementioned configurations of the subscriber stations (10, 20, 30) of the bus system (1) and the methods executed within them may be used individually or in any possible combination. In particular, all features of the aforementioned embodiments and / or variations thereof may be combined at will. In addition to, or alternatively, the following variations may be considered.

[0121] Although the present invention has been described above using a CAN bus system as an example, the present invention can be used in any communication network and / or communication method in which two different communication stages are used, in which bus states generated for different communication stages are distinguished from each other. In particular, the present invention can be used in the development of other serial communication networks such as Ethernet and / or 100 Base-T1 Ethernet, field bus systems, etc.

[0122] In particular, the bus system (1) according to the embodiments may be a communication network in which data can be transmitted serially at two different bit rates. In the bus system (1), it is desirable, but not mandatory, to ensure that collision-free exclusive access of subscriber stations (10, 20, 30) to one common channel is guaranteed for at least a fixed time interval.

[0123] The number and arrangement of subscriber stations (10, 20, 30) within the bus system (1) of the embodiments are optional. In particular, subscriber station (20) may be omitted within the bus system (1). One or more subscriber stations (10 or 30) may be provided within the bus system (1). It is also possible to consider cases where all subscriber stations within the bus system (1) are configured identically, that is, cases where only subscriber station (10) exists or only subscriber station (30) exists.

Claims

Claim 1 As a subscriber station (10; 30) for a serial bus system (1), the subscriber station comprises a communication control device (11; 31) for controlling communication between the subscriber station (10; 30) and one or more other subscriber stations (10; 20; 30) of the bus system (1); and a transmitting / receiving device (12; 32) configured to serially transmit a transmission signal (TXD) generated by the communication control device (11; 31) to the bus (40) of the bus system (1) and serially receive a signal from the bus (40) of the bus system (1); wherein the communication control device (11; 31) is configured to generate a transmission signal (TXD) according to a frame (450; 450_1; 450_2), and to insert a header checksum (HCRC) for protecting the header of the frame (450; 450_1; 450_2) and a frame checksum (FCRC) for protecting the entire frame of the frame (450; 450_1; 450_2) into the frame (450; 450_1; 450_2), respectively; and the communication control device (11; 31) is configured such that a reverse stuff bit after five identical bits is the A subscriber station (10; 30) for a serial bus system, configured to insert dynamic stuff bits into the frames (450; 450_1; 450_2) in a manner that inserts them into the bit stream of the frames (450; 450_1; 450_2), wherein the communication control device (11; 31) is configured to calculate the two checksums (HCRC, FCRC) in such a manner that at most one of the two checksums (HCRC, FCRC) includes the dynamic stuff bits in the calculation, and the header of the frames (450; 450_1; 450_2; 4500; 4500_1; 4500_2) protected by the header checksum (HCRC) does not include bits that always have a fixed value, and includes only bits that have values ​​that can be changed by the communication control device (11; 31) among the headers of the frames. Claim 2 A subscriber station (10; 30) for a serial bus system, wherein the communication control device (11; 31) is configured to insert a first field (SBC) coded with the number of dynamic stuff bits into a frame (450; 450_1; 450_2), and the communication control device (11; 31) is configured to insert at least one first field (SBC) before a data field (455) into which user data of the frame (450; 450_1; 450_2) is inserted. Claim 3 In claim 1 or 2, the transmitting / receiving device (12; 32) for serially transmitting a transmission signal (TXD) generated by the communication control device (11; 31) to the bus (40) of the bus system (1) is configured such that, for a message (45) exchanged between the subscriber stations (10, 20, 30) of the bus system (1), the bit time (t_bt) of the signal transmitted to the bus (40) in the first communication stage (451) may be different from the bit time (t_bt) of the signal transmitted in the second communication stage (452). Claim 4 In claim 1 or 2, the communication control device (11; 31) has a second field (FCP) configured to check whether the bit stream of a frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2) is offset by at least one bit compared to an expected frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2) at a subscriber station (10; 20; 30) of a bus system (1) that has received but has not transmitted a frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2) A subscriber station (10; 30) for a serial bus system configured to insert, wherein the communication control device (11; 31) is configured to insert at least one second field (FCP) after a data field (455) within a frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2), particularly to insert at least one field (FCP) after a frame checksum (FCRC) generated across all bits within the frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2). Claim 5 In claim 4, the communication control device (11; 31) is configured to insert a synchronization field (SYN) having two bits having different values ​​after at least one second field (FCP) within a frame (450_1; 4500_1), and accordingly, the bits form a synchronization edge arranged to switch the bit rate for transmitting a transmission signal to the bus (40) according to a bit pattern and / or to switch the physical layer of the transmitting / receiving device (12; 32), a subscriber station (10; 30) for a serial bus system. Claim 6 A subscriber station (10; 30) for a serial bus system, wherein, in claim 1 or 2, a frame (450; 450_1) formed for a message (45) is configured to be compatible with CAN FD, and in a first communication step (451), it is agreed which of the subscriber stations (10, 20, 30) of the bus system (1) obtains at least temporarily conflict-free exclusive access rights to the bus (40) in a subsequent second communication step (452). Claim 7 A bus system (1) having a bus (40); and two or more subscriber stations (10; 20; 30) connected to each other via the bus (40) so as to communicate with each other in series, wherein at least one of the subscriber stations (10; 30) is a subscriber station (10; 30) according to claim 1 or 2. Claim 8 A method for communication in a serial bus system (1), said method is executed by a subscriber station (10; 30) of the bus system (1) having a communication control device (11; 31) and a transmitting / receiving device (12; 32), said method comprising: a step of controlling communication between the subscriber station (10; 30) and one or more other subscriber stations (10; 20; 30) of the bus system (1) using said communication control device (11; 31); a step of transmitting a transmission signal (TXD) generated by said communication control device (11; 31) to a bus (40) of the bus system (1) using said transmitting / receiving device (12; 32); wherein said transmitting / receiving device (12; 32) is also configured to serially receive a signal from the bus (40) of the bus system (1); The method includes the step of generating a transmission signal (TXD) according to a frame (450; 450_1; 450_2) using the communication control device (11; 31); wherein the communication control device (11; 31) inserts a header checksum (HCRC) for protecting the header of the frame (450; 450_1; 450_2) and a frame checksum (FCRC) for protecting the entire frame of the frame (450; 450_1; 450_2) into the frame (450; 450_1; 450_2), respectively; and the communication control device (11; 31) inserts a dynamic stuff bit into the frame (450; 450_1; 450_2) in such a manner that a reverse stuff bit is inserted into the bit stream of the frame (450; 450_1; 450_2) after five identical bits, and the A communication control device (11; 31) calculates the two checksums (HCRC, FCRC) in such a way that at most one of the two checksums (HCRC, FCRC) includes dynamic stuff bits in the calculation, and the header of the frame (450; 450_1; 450_2; 4500; 4500_1; 4500_2) protected by the header checksum (HCRC) does not always include bits having a fixed value, and among the headers of the frame, the communication control device (11;A communication method in a serial bus system comprising only bits having values ​​changeable by 31).

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