Communication control device and transmit / receive device for a participant station of a serial bus system and method for communication in a serial bus system

Description

Technical field

[0001] The present invention relates to a communication control device and a transmit / receive device for a subscriber station of a serial bus system and a method for communication in a serial bus system that operates with high data rate and high error robustness. State of the art

[0002] For communication between sensors and control units, for example in vehicles, a bus system is frequently used in which data is transmitted as messages in the standard ISO 11898-1:2015 as a CAN protocol specification with CAN FD. The messages are transmitted between the bus participants of the bus system, such as sensors, control units, transmitters, etc.

[0003] DE 10 2006 019 305 A1 describes a method for data transmission to and from a control unit, in particular an engine control unit for a motor vehicle. The control unit has a first communication interface and a second communication interface. The first communication interface can be used for bidirectional communication with a development tool or, alternatively, can be switched to a CAN bus. The second communication interface is intended only for communication within the CAN bus. Data transmission between the control unit and the development tool can occur simultaneously with communication from the control unit within the CAN bus.

[0004] To transmit data at a higher bit rate than CAN offers, the CAN FD message format includes an option to switch to a higher bit rate within a message. This increases the maximum possible data rate beyond 1 Mbit / s by using a higher clock frequency in the data fields. Such messages are subsequently referred to as CAN FD frames or CAN FD messages. With CAN FD, the payload length is extended from 8 to up to 64 bytes, and the data transmission rates are significantly higher than with CAN.

[0005] To transmit data faster from the sending bus participant to the receiving bus participant than with CAN FD, a successor bus system to CAN FD, called CAN XL, is currently under development. This system aims to offer not only a higher data rate during the data phase than CAN FD, but also an increase in the maximum payload length of up to 64 bytes, a feat previously achieved with CAN FD. However, the successor bus system is also intended to retain the robustness advantages of a CAN or CAN FD-based communication network.

[0006] The faster the data is transmitted on the bus, the higher the demands on the quality of the signal that the protocol controller of the receiving station receives from the bus. For example, if the slew rate of the bits in the received signal is too low, this can lead to highly asymmetric bits, and thus the received signal may not be decoded correctly.

[0007] Increasing the slew rate of the received signal's bits results in excessive radiation. This leads to increased costs elsewhere, for example on the circuit board and in the microcontroller for the receiving station. Disclosure of the invention

[0008] Therefore, the object of the present invention is to provide a communication control device and a transmit / receive device for a subscriber station of a serial bus system, and a method for communication in a serial bus system, which solve the aforementioned problems. In particular, a communication control device and a transmit / receive device for a subscriber station of a serial bus system, and a method for communication in a serial bus system, are to be provided in which a high data rate and an increase in the amount of user data per frame can be achieved with high error robustness.

[0009] The problem is solved by a communication control device for a participant station of a serial bus system with the features of claim 1. The communication control device has a communication control module for generating a transmit signal for controlling communication between the participant station and at least one other participant station of the bus system, in which the bus system uses at least a first communication phase and a second communication phase for exchanging messages between participant stations of the bus system; a first connection for transmitting, in an operating mode of the first communication phase, the transmit signal to a transmit / receive device configured for transmitting the transmit signal to a bus of the bus system; and a second connection for receiving, in the operating mode of the first communication phase, a digital receive signal from the transmit / receive device.and an operating mode switching module for switching the transmission direction of the first and second terminals in the second communication phase in the same direction for differential signal transmission via the first and second terminals, as described in claim 1.

[0010] The communication control unit makes it possible to provide the required fast data transmission with very high bit symmetry for the CAN FD successor bus system without additional expensive connections between the communication control unit and the transmit / receive unit.

[0011] The communication control unit is advantageously designed such that the symmetry of the bits in a received signal RxD is preserved. This signal is generated by the transmit / receive unit from a signal received from the bus and sent to the communication control unit. This applies to both the sending and receiving of CAN frames, including the transmitted signal TxD.

[0012] Furthermore, even with differential transmission of the received signal RxD between the transmit / receive device (transceiver) and the communication control device (microcontroller), NRZ encoding (NRZ = Non-Return-To-Zero) can be retained. As a result, pins with slow edges can now be used for data transmission between the transmit / receive device (transceiver) and the communication control device (microcontroller). The resulting lower edge steepness of the bits in the received and transmitted signals significantly reduces the system's radiation.

[0013] Thus, the bit edge steepness of the received and transmitted signals can be selected to easily meet the transmission requirements. Furthermore, the communication control unit does not need to use complex line coding methods, such as PWM coding or Manchester coding, to maintain signal symmetry. This reduces the complexity of data transmission and decoding of the transmitted signal (TxD) and received signal (RxD).

[0014] Furthermore, the communication control unit can maintain a CAN-like arbitration in one of the communication phases while still significantly increasing the transmission rate compared to CAN or CAN FD. This is achieved by using two communication phases with different bit rates and reliably indicating to the transmit / receive device the start of the second communication phase, in which the user data is transmitted at a higher bit rate than in the arbitration. Therefore, the transmit / receive device can reliably switch from the first to the second communication phase.

[0015] As a result, a significant increase in the bit rate and thus the transmission speed from sender to receiver is achievable. At the same time, high error robustness is guaranteed. This contributes to achieving a net data rate of at least 10 Mbps. Furthermore, the size of the user data can be larger than 64 bytes, in particular up to 2048 bytes per frame, or any length as required.

[0016] The procedure performed by the communication control unit can also be used if the bus system also contains at least one CAN participant station and / or at least one CAN FD participant station that sends messages according to the CAN protocol and / or CAN FD protocol.

[0017] Further advantageous configurations of the communication control device are specified in the dependent claims.

[0018] The operating mode switching module can be configured to, in a first operating mode of the second communication phase, switch the first and second terminals as outputs and generate an inverse digital transmit signal from the transmit signal, as well as output the transmit signal at the first terminal and the inverse digital transmit signal at the second terminal. Additionally or alternatively, the operating mode switching module can be configured to, in a second operating mode of the second communication phase, switch the first and second terminals as inputs and generate a non-differential receive signal from the differential receive signal received at the first and second terminals, and output it to the communication control module.

[0019] According to one embodiment, the operating mode switching module is designed to generate and output the two transmitted signals at the same level at the two terminals for a predetermined period of time in the first operating mode of the second communication phase, in order to signal to the transmit-receive device that the operating mode of the transmit-receive device is to be switched from the first operating mode of the second communication phase to the operating mode of the first communication phase.

[0020] According to one embodiment, the operating mode switching module is designed to signal to the transmit-receive device via the first or second connection that the transmit-receive device is to switch its operating mode from the operating mode of the first communication phase to a predetermined operating mode of the second communication phase.

[0021] For example, the communication control module is designed to generate the transmit signal in the first communication phase with bits having a first bit time that is at least 10 times larger than the second bit time of bits that the communication control module generates in the second communication phase in the transmit signal.

[0022] The aforementioned problem is also solved by a transmitting / receiving device for a subscriber station of a serial bus system with the features of claim 6.The transmit / receive device has a transmit / receive module for sending a transmit signal to a bus of the bus system, in which the bus system uses at least a first communication phase and a second communication phase for exchanging messages between subscriber stations of the bus system, and for generating a digital receive signal from a signal received from the bus, a first connection for receiving, in an operating mode of the first communication phase, a transmit signal from a communication control device, a second connection for sending, in an operating mode of the first communication phase, the digital receive signal to the communication control device, and an operating mode switching module for switching the transmission direction of the first and second connections in the second communication phase to the same direction for differential signal transmission via the first and second connections, as described in claim 6.

[0023] The transmitting / receiving device offers the same advantages as previously mentioned in relation to the communication control device. Further advantageous embodiments of the transmitting / receiving device are specified in the dependent claims.

[0024] The operating mode switching module can be configured to switch the first and second terminals as inputs in a first operating mode of the second communication phase and to generate a non-differential transmit signal from the differential digital transmit signal received at the first and second terminals. Alternatively, the operating mode switching module can be configured to switch the first and second terminals as outputs in a second operating mode of the second communication phase and to generate an inverse digital receive signal from the digital receive signal, as well as outputting the digital receive signal at the second terminal and the inverse digital receive signal at the first terminal.

[0025] According to one embodiment, the operating mode switching module is designed to generate and output the two received signals at the same level at the two terminals for a predetermined period of time in the second operating mode of the second communication phase, in order to signal additional information to the communication control device, which is in addition to information from the signals exchanged in the bus system with the messages between participant stations of the bus system.

[0026] Optionally, the transmit / receive module is designed to send the transmit signal as a differential signal to the bus.

[0027] The operating mode switching module can be designed to select the transmission direction of the first and second connections depending on the operating mode in which the transmitting / receiving device is switched.

[0028] The devices described above may also include a direction control block for controlling the transmission direction of the first and second terminals depending on the operating mode of the transmit / receive device, a coding block for encoding the differential signals, a decoding block for decoding the differential signal at the first and second terminals into a non-differential signal, and a multiplexer for outputting the non-differential signal generated by the decoding block when the transmit / receive device is switched to a second-phase communication operating mode.

[0029] According to one option, the signal received by the bus in the first communication phase is generated with a different physical layer than the signal received by the bus in the second communication phase.

[0030] It is conceivable that in the first communication phase, it is negotiated which of the participating stations of the bus system will receive at least temporary exclusive, collision-free access to the bus in the subsequent second communication phase.

[0031] The communication control unit and the transmit / receive unit described above can be part of a subscriber station in a bus system, which also includes a bus and at least two subscriber stations connected to each other via the bus in such a way that they can communicate serially. In this case, at least one of the at least two subscriber stations has a communication control unit and a transmit / receive unit as described above.

[0032] The aforementioned problem is further solved by a method for communication in a serial bus system according to claim 15. The method is implemented with a participant station for a bus system in which at least a first communication phase and a second communication phase are used for exchanging messages between participant stations of the bus system, wherein the participant station has a previously described communication control device and a previously described transmit / receive device, and wherein the method comprises the steps of switching, with an operating mode switching module for the communication control device, the transmission direction of the first and second connections for the communication control device in the second communication phase in the same direction, and switching, with an operating mode switching module for the transmit / receive device,the transmission direction of the first and second terminals for the transmit / receive device in the second communication phase in the same direction, which differs from the direction in which the first and second terminals for the communication control device are connected, and performing a differential signal transmission between the communication control device and the transmit / receive device via the first and second terminals for the communication control device and the first and second terminals for the transmit / receive device, as described in claim 15.

[0033] The procedure offers the same advantages as previously mentioned in relation to the communication control device and / or the transmitting / receiving device.

[0034] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention. Drawings

[0035] The invention is described in more detail below with reference to the accompanying drawing and by means of exemplary embodiments. The drawing shows: Fig. 1 a simplified block diagram of a bus system according to a first embodiment; Fig. 2 a diagram illustrating the structure of messages that can be sent by participant stations of the bus system according to the first embodiment; Fig. 3 a simplified schematic block diagram of a participant station of the bus system according to the first embodiment; Figs. 4 to 7each a temporal representation of signals or states at the participating station of Fig. 3 , if the participating station is the sender of a message sent via a bus of the bus system; Figs. 8 to 11 each a temporal representation of signals or states at the participating station of Fig. 3 , if the participating station is the receiver of a message sent over the bus of the bus system; and Figs. 12 to 16 each a temporal representation of signals or states at the participating station of Fig. 3 In a second embodiment, the participating station is the sender of a message sent via the bus of the bus system in the data phase and switches back from the data phase to the arbitration phase.

[0036] In the figures, identical or functionally equivalent elements are provided with the same reference symbols unless otherwise specified. Description of the exemplary implementations

[0037] Fig. 1 Figure 1 shows, as an example, a bus system 1, which is fundamentally designed for a CAN bus system, a CAN FD bus system, a CAN FD successor bus system, and / or variations thereof, as described below. The CAN FD successor bus system is referred to below as CAN XL. Bus system 1 can be used in a vehicle, in particular a motor vehicle, an aircraft, etc., or in a hospital, etc.

[0038] In Fig. 1Bus system 1 has a multitude of terminal stations 10, 20, 30, each connected to a bus 40 with a first bus wire 41 and a second bus wire 42. The bus wires 41 and 42 can also be called CAN_H and CAN_L, respectively, and serve for electrical signal transmission after coupling the dominant levels or generating recessive levels for a signal in the transmit state. Messages 45 and 46 in the form of signals can be transmitted serially between the individual terminal stations 10, 20, and 30 via bus 40. The terminal stations 10, 20, and 30 are, for example, control units, sensors, display devices, etc., of a motor vehicle.

[0039] As in Fig. 1As shown, subscriber station 10 has a communication control unit 11, a transceiver 12, a first operating mode switching module 15, and a second operating mode switching module 16. In contrast, subscriber station 20 has a communication control unit 21 and a transceiver 22. Subscriber station 30 has a communication control unit 31, a transceiver 32, a first operating mode switching module 35, and a second operating mode switching module 36. The transceivers 12, 22, and 32 of subscriber stations 10, 20, and 30 are each directly connected to bus 40, even though this is shown in Fig. 1 is not illustrated.

[0040] At each subscriber station 10, 20, 30, the messages 45, 46 are encoded as frames and exchanged bit-by-bit via a TXD line and an RXD line between the respective communication control unit 11, 21, 31 and the associated transmit / receive units 12, 22, 32. This is described in more detail below.

[0041] The communication control devices 11, 21, 31 each serve to control communication between the respective subscriber station 10, 20, 30 via bus 40 with at least one other subscriber station of the subscriber stations 10, 20, 30 that are connected to bus 40.

[0042] The communication control units 11, 31 create and read initial messages 45, which are, for example, modified CAN messages 45, hereinafter also referred to as CAN XL messages 45. The CAN XL messages 45 are based on a successor format to CAN FD, which, with regard to Fig. 2is described in more detail. The communication control devices 11, 31 can also be configured to provide or receive a CAN XL message 45 or a CAN FD message 46 for the transmit / receive devices 12, 32, as required. The communication control devices 11, 31 thus create and read a first message 45 or a second message 46, the first and second messages 45, 46 differing in their data transmission standard, namely in this case CAN XL or CAN FD.

[0043] The communication control unit 21 can be implemented like a conventional CAN controller according to ISO 11898-1:2015, in particular like a CAN FD-tolerant Classical CAN controller or a CAN FD controller. The communication control unit 21 creates and reads secondary messages 46, for example, Classical CAN messages or CAN FD messages 46. CAN FD messages 46 can contain from 0 to 64 data bytes, which are also transmitted at a significantly faster data rate than a Classical CAN message. In the latter case, the communication control unit 21 is implemented like a conventional CAN FD controller.

[0044] The transceiver units 12 and 32 can be implemented as CAN XL transceivers, with the exception of the differences described in more detail below. The transceiver units 12 and 32 can also be implemented as conventional CAN FD transceivers, either additionally or alternatively. The transceiver unit 22 can be implemented as either a conventional CAN transceiver or a CAN FD transceiver.

[0045] With the two participant stations 10, 30, the formation and then transmission of messages 45 with the CAN XL format as well as the reception of such messages 45 is possible.

[0046] Fig. 2Figure 45 shows a CAN XL frame 450 as sent by the transmit / receive device 12 or the transmit / receive device 32. The CAN XL frame 450 is divided into different communication phases 451 to 455 for CAN communication on bus 40: an arbitration phase 451, a first switching phase 452, a data phase 453, a second switching phase 454, and a frame end phase 455.

[0047] In arbitration phase 451, for example, a bit is sent at the beginning, also called the SOF bit, which indicates the start of the frame. Also in arbitration phase 451, an identifier, for example with 11 bits, is sent to identify the sender of message 45. During arbitration, the identifier is used to negotiate bit-by-bit between participating stations 10, 20, and 30 which station wants to send message 45, 46 with the highest priority and therefore receives exclusive access to bus 40 of bus system 1 for sending during switching phase 452 and the subsequent data phase 453.

[0048] In the first switching phase 452, the switch from the arbitration phase 451 to the data phase 453 is prepared in the present embodiment. The switching phase 452 can contain a bit that has the bit duration T_B1 of a bit in the arbitration phase 451 and is transmitted at least partially with the physical layer of the arbitration phase 451. The first switching phase 452 logically belongs to the arbitration phase 451. In particular, in this switching phase 452, the transmit / receive device 12, 32 is signaled to switch to a different mode or operating mode, namely to the physical layer of the data phase 453.

[0049] In data phase 453, the bits of frame 450 are transmitted using the physical layer of data phase 453 and with a bit duration T_B2 that is shorter than the bit duration T_B1 of a bit in arbitration phase 451. Data phase 453 transmits, among other things, the payload of the CAN XL frame 450, or message 45. This payload can also be referred to as the data field of message 45. For this purpose, a data-length code, for example, 11 bits long, can be transmitted in data phase 453 after a data field identifier that identifies the type of content in the data field. The code can, for example, take values ​​from 1 to 2048 or any other value with a step size of 1. Alternatively, the data-length code can comprise fewer or more bits, so that the value range and step size can be different. This is followed by other fields, such as the header checksum field. Then the user data of the CAN XL frame 450 or...Message 45 is sent. At the end of data phase 453, a checksum field can contain, for example, a checksum over the data of data phase 453 and the data of arbitration phase 451. The sender of message 45 can insert stuff bits as inverse bits into the data stream after a predetermined number of identical bits, in particular 10 identical bits. Specifically, the checksum is a frame checksum F_CRC, with which all relevant bits of frame 450 up to the checksum field are secured. Stuff bits in data phase 453, for example, are not secured because these bits secure frame 450 itself and are therefore used for error detection.

[0050] In the second switching phase 454, the switch from the data phase 453 to the frame-end phase 455 is prepared in the present embodiment. This means that the system switches back to the transmission mode according to the arbitration phase 451. The switching phase 454 can contain a bit that has the bit duration T_B1 of a bit in the arbitration phase 451 and is transmitted at least partially with the physical layer of the data phase 453. The second switching phase 454 logically belongs to the frame-end phase 455, in which the same transmission mode is used as in the arbitration phase 451. In particular, in this second switching phase 454, the transmit / receive device 12, 32 is signaled to switch to a different mode or operating mode, namely to the physical layer of the arbitration phase 451.

[0051] In the frame end phase 455, after two bits AL2 and AH2 in an end field, at least one acknowledge bit (ACK) can be present. This can be followed by a sequence of seven identical bits, indicating the end of the CAN XL frame 450. The at least one acknowledge bit (ACK) allows a receiver to indicate whether or not it has correctly received the CAN XL frame 450 or the message 45.

[0052] At least in the arbitration phase 451 and the frame completion phase 455, a physical layer similar to that used in CAN and CAN-FD is employed. Additionally, in the switching phases 452 and 454, a physical layer similar to that used in CAN and CAN-FD can be used at least partially, i.e., at the beginning of the first switching phase 452 and at the end of the second switching phase 454. This physical layer corresponds to the physical layer or layer 1 of the well-known OSI model (Open Systems Interconnection model).

[0053] An important point during these phases 451 and 455 is the use of the well-known CSMA / CR protocol, which allows simultaneous access to bus 40 by participant stations 10, 20, and 30 without destroying the higher-priority message 45 or 46. This makes it relatively easy to add further bus participant stations 10, 20, and 30 to bus system 1, which is very advantageous.

[0054] The CSMA / CR method results in so-called recessive states on bus 40, which can be overwritten by other participant stations 10, 20, 30 with dominant states on bus 40.

[0055] Arbitration at the beginning of frame 450 or message 45, 46, and acknowledgment in the frame-end phase 455 of frame 450 or message 45, 46, are only possible if the bit duration or bit time is significantly more than twice the signal propagation time between any two subscriber stations 10, 20, 30 of bus system 1. Therefore, the bit rate in the arbitration phase 451 and the frame-end phase 454 is chosen to be slower than in the data phase 453 of frame 450. Specifically, the bit rate in phases 451 and 455 is chosen to be 500 kbit / s, resulting in a bit duration or bit time of approximately 2 µs, whereas the bit rate in the data phase 453 is chosen to be 5 to 10 Mbit / s or more, resulting in a bit time of approximately 0.1 µs or less. This follows. Thus, the bit time of the signal in the other communication phases 451, 452, 454, 455 is at least 10 times greater than the bit time of the signal in the data phase 453.

[0056] A sender of message 45, for example, subscriber station 10, only begins transmitting bits of the switching phase 452 and the subsequent data phase 453 to bus 40 once subscriber station 10, as the sender, has won the arbitration and thus has exclusive access to bus 40 of bus system 1 for transmission. The sender can either switch to the faster bit rate and / or the other physical layer after part of the switching phase 452, or switch to the faster bit rate and / or the other physical layer only with the first bit, i.e., with the beginning of the subsequent data phase 453.

[0057] In general, the following different properties can be implemented in the CAN XL bus system compared to CAN or CAN FD: a) Adoption and, if necessary, adaptation of proven features that are responsible for the robustness and user-friendliness of CAN and CAN FD, in particular frame structure with identifier and arbitration according to the CSMA / CR method, b) Increase of the net data transmission rate to approximately 10 megabits per second, c) Increase of the size of the payload data per frame to approximately 2 kilobytes or to any desired value.

[0058] Fig. 3 Figure 1 shows the basic structure of the subscriber station 10 with the communication control unit 11, the transceiver 12, and the operating mode switching modules 15 and 16. The operating mode switching module 15 of the communication control unit 11 is symmetrical to the operating mode switching module 16 of the transceiver 12. The operating mode switching module 15 can also be called the first operating mode switching module. The operating mode switching module 16 can also be called the second operating mode switching module.

[0059] Participant station 30 is set up in a similar way to the one in Fig. 3 The following is shown, except that block 35 is not integrated into the communication control unit 31, but is provided separately from the communication control unit 31 and the transmit / receive unit 32. Therefore, the subscriber station 30 and block 35 are not described separately. The functions of the operating mode switching module 15 described below are identical in the operating mode switching module 35. The functions of the operating mode switching module 16 described below are identical in the operating mode switching module 36.

[0060] Alternatively or additionally, it is possible that the block 16 is not integrated into the transmit / receive device 12, but is provided separately from the communication control device 11 and the transmit / receive device 12.

[0061] The transmit / receive device 12 is connected to the bus 40, more precisely its first bus wire 41 for CAN_H and its second bus wire 42 for CAN_L. In the operation of bus system 1, the transmit / receive device 12 converts a transmit signal TxD from the communication control device 11 into corresponding signals CAN_H and CAN_L for the bus wires 41 and 42 and transmits these signals CAN_H and CAN_L to bus 40. Although the signals CAN_H and CAN_L are mentioned here for the transmit / receive device 12, with regard to message 45 they are to be understood as signals CAN-XL_H and CAN-XL_L, which differ from the conventional signals CAN_H and CAN_L in at least one characteristic during data phase 453, in particular with regard to the formation of the bus states for the different data states of the signal TxD and / or with regard to the voltage or the physical layer and / or the bit rate.

[0062] A differential signal VDIFF = CAN_H - CAN_L is generated on bus 40. Except in idle or standby mode, the transceiver 12 and its receiver are always listening for data or message transmissions 45, 46 on bus 40 during normal operation, regardless of whether the receiving station 10 is the sender of message 45 or not. The transceiver 12 generates a receive signal RxD from the CAN_H and CAN_L signals received from bus 40 and forwards this signal to the communication control unit 11, as described in more detail below.

[0063] The following described setup of the subscriber station 10 provides a robust and simple way to transmit bits symmetrically between the communication control unit 11 and the transmit / receive unit 12 using signals, i.e., without the duration of the bits changing. This is particularly advantageous during data transmission during data phase 453 of a frame 450.

[0064] According to Fig. 3The communication control unit 11 has, in addition to the operating mode switching module 15, a first bidirectional connection 111 for a digital transmit signal TxD, a second bidirectional connection 112 for a digital receive signal RxD, and a communication control module 113. The transmit / receive unit 12 has, in addition to the operating mode switching module 16, a first bidirectional connection 121 for the digital transmit signal TxD, a second bidirectional connection 122 for the digital receive signal RxD, and a transmit / receive module 123. Connections 111, 112, 121, and 122 can be operated bidirectionally using modules 15 and 16 and corresponding signals, namely, they can be switched either as an output or an input, as described below.

[0065] The communication control unit 11 is designed as a microcontroller or incorporates a microcontroller. The communication control unit 11 processes signals from any application, such as a control unit for a motor, a safety system for a machine or vehicle, or other applications. Not shown, however, is a system ASIC (application-specific integrated circuit), which could alternatively be a system base chip (SBC) on which several functions necessary for an electronic assembly of the receiving station 10 are integrated. The system ASIC may, among other things, incorporate the transmitter / receiver unit 12 and a power supply unit (not shown) that provides electrical power to the transmitter / receiver unit 12. The power supply unit typically provides a CAN_Supply voltage of 5 V.Depending on requirements, the power supply unit can provide a different voltage with a different value and / or be designed as a current source.

[0066] The Communication Control Module 113 is a protocol controller that implements the CAN protocol, specifically the CAN XL or CAN FD protocols. The Communication Control Module 113 is designed to output the following signals or receive the following input signals.

[0067] The signal TxD_PRT is an output signal corresponding to the transmitted signal TxD. The signal RxD_PRT is an input signal corresponding to the received signal RxD.

[0068] In addition to these signals, the communication control module 113 is designed to generate and output the following control signals TX_DM, RX_DM.

[0069] The control signal TX_DM is an output signal and indicates whether the transceiver 12 should operate in TX-DataPhaseMode or not. This operating mode is also called FAST_TX Mode or first operating mode. In TX-DataPhaseMode, the receiving station 10 has won the arbitration in arbitration phase 451 and is the sender of frame 450 in the subsequent data phase 453. In this case, the receiving station 10 can also be referred to as the transmitting node. In TX-DataPhaseMode, the transceiver 12 should use the physical layer for data phase 453 and drive the bus wires CAN_H and CAN_L.

[0070] The control signal RX_DM is an output signal and indicates whether the transceiver 12 should operate in RX-DataPhaseMode or not. This operating mode is also called FAST_RX Mode or the second operating mode. In RX-DataPhaseMode, the receiving station 10 has lost arbitration in arbitration phase 451 and is only a receiver, i.e., not a transmitter, of frame 450 in the subsequent data phase 453. In this case, the receiving station 10 can also be referred to as a receiving node. In RX-DataPhaseMode, the transceiver 12 should use the physical layer for data phase 453 but should not drive the CAN_H and CAN_L bus wires.

[0071] If the transmit / receive device is neither in TX-DataPhaseMode nor in RX-DataPhaseMode, it is in so-called ArbitrationPhaseMode, the mode used in the arbitration phase 451 and the frame end phase 455. In this mode, the physical layer is used, which allows dominant and recessive bus states to be transmitted.

[0072] The circuit for signaling the operating mode to be activated to the transmit / receive unit 12 is not shown here. Signaling is also effected, in particular, via the TxD port 111 and / or the RxD port 112.

[0073] The operating mode switching module 15 has a direction control block 151, a coding block 152, a decoding block 153 and a multiplexer 154. The first operating mode switching module 15 receives the aforementioned signals, which are output by the communication control module 113.

[0074] The direction control block 151 generates the switching signals DIR_TxD and DIR_RxD from the control signals TX_DM and RX_DM of the communication control module 113. The switching signal DIR_TxD controls the direction DIR, more precisely the transmission direction, of the first bidirectionally switchable port 111 of the communication control device 11. In other words, the switching signal DIR_TxD controls the direction of the TxD port 111 of the device 11. The switching signal DIR_RxD controls the direction DIR, more precisely the transmission direction, of the second bidirectionally switchable port 112 of the communication control device 11. In other words, the switching signal DIR_RxD controls the direction of the RxD port 112 of the device 11.

[0075] If the TX_DM signal is set, specifically if its signal value is 1, then the direction of the TxD port 111 and the direction of the RxD port 112 are set to output. As a result, the communication control module 113 can send a frame 450 to bus 40 as a differential signal via ports 111 and 112, as described in more detail below. Specifically, if the communication control module 113 sends a frame 450 and the TX_DM signal is set, then the direction of the TxD port 111 and the direction of the RxD port 112 are set to output.

[0076] If the RX_DM signal is set, in particular if its signal value is 1, then the direction of the TxD port 111 and the direction of the RxD port 112 are switched to input. As a result, the communication control module 113 can receive a frame 450 transmitted via bus 40 as a differential signal via ports 111 and 112, as described in more detail below. In particular, if the communication control module 113 receives a frame 450 and the RX_DM signal is set, then the direction of the TxD port 111 and the direction of the RxD port 112 are switched to input.

[0077] Coding block 152 generates a signal TxD2 from the signal TxD_PRT, i.e., the transmit signal TxD. Signal TxD2 is the inverse of signal TxD_PRT. ​​Coding block 152 outputs signal TxD2 to terminal 112. If terminals 111 and 112 are configured as outputs, as previously described, the communication control unit 11 can output the signals TxD_PRT and TxD2 as a differential output signal to the transmit / receive unit 12 via terminals 111 and 112. In the simplest case, coding block 152 is an inverter that inverts the signal TxD_PRT.

[0078] The decode block 153 is connected to terminals 111 and 112 at its input. When terminals 111 and 112 are set to input, as previously described, the decode block 153 receives a differential input signal from terminals 111 and 112, consisting of a signal RxD1 and a signal RxD2. The decode block 153 decodes the signals RxD1 and RxD2 to the non-differential signal RxD_PRT. ​​The decode block 153 outputs the signal RxD_PRT to the multiplexer 154.

[0079] The communication control module 113 controls the multiplexer 154 with the control signal RX_DM. Depending on the signal value of the control signal RX_DM, a selection is made as to whether the communication control module 113 receives the signal decoded by the decoding block 153 or the signal RxD1 from the terminal 112 as signal RxD_PRT.

[0080] In the transceiver 12, the transceiver module 123 is designed to send and / or receive messages 45, 46 according to the CAN protocol, in particular messages according to the protocol for CAN XL or CAN FD, as described above. The transceiver module 123 provides the connection to the physical medium, i.e., bus 40 with bus wires 41, 42. The transceiver module 123 drives and decodes the CAN_H and CAN_L signals for bus wires 41, 42 and bus 40, respectively. The transceiver module 123 is also designed to output the following output signals or receive the following input signals.

[0081] The RxD_TC signal is an output signal corresponding to a digital receive signal generated by the transceiver module 123 from the differential CAN_H, CAN_L signal on bus 40. The TxD_TC signal is an input signal corresponding to the TxD transmit signal, i.e., the signal generated by the communication control module 113 for transmission to bus 40.

[0082] In addition to these signals, the transmit / receive module 123 is designed to generate and output the following control signals TX_DM_TC, RX_DM_TC.

[0083] The control signal TX_DM_TC is an output signal and indicates whether the transceiver 12 is operating in TX-DataPhaseMode mode or not, in order to act as the transmitter of the frame 450 in data phase 453, as described previously. This is an operating mode in which the transceiver module 123 sends bits on bus 40 in data phase 453, thus driving bus 40.

[0084] The control signal RX_DM_TC is an output signal and indicates whether the transceiver 12 is operating in RX-DataPhaseMode or not, in order to act only as a receiver, and not as a transmitter, of frame 450 in data phase 453, as described previously. This is an operating mode in which the transceiver module 123 receives bits only from bus 40 in data phase 453, and thus does not drive bus 40.

[0085] The second operating mode switching module 16 has a direction control block 161, a coding block 162, a decoding block 163 and a multiplexer 164. The second operating mode switching module 16 receives the aforementioned signals which are output by the transmit / receive module 123.

[0086] The direction control block 161 generates the switching signals DIR_TxD_TC and DIR_RxD_TC from the control signals TX_DM_TC and RX_DM_TC of the transmit / receive module 123. The switching signal DIR_TxD_TC controls the direction DIR, more precisely the transmission direction, of the first bidirectionally switchable port 121 of the transmit / receive device 12. In other words, the switching signal DIR_TxD_TC controls the direction of the TxD port 121 of the device 12. The switching signal DIR_RxD_TC controls the direction DIR, more precisely the transmission direction, of the second bidirectionally switchable port 122 of the transmit / receive device 12. In other words, the switching signal DIR_RxD_TC controls the direction of the RxD port 122 of the device 12.

[0087] If the RX_DM_TC signal is set, and in particular if its signal value is 1, then the direction of the TxD port 121 and the direction of the RxD port 122 are switched to output. As a result, the transmit / receive module 123 can send a frame 450 transmitted by another subscriber station via bus 40 as a differential signal via ports 121 and 122 to the communication control unit 11, as described in more detail below. Specifically, if the transmit / receive module 123 receives a frame 450 and the RX_DM_TC signal is set, then the direction of the TxD port 121 and the direction of the RxD port 122 are switched to output.

[0088] If the TX_DM_TC signal is set, in particular if its signal value is equal to 1, then the direction of the TxD port 121 and the direction of the RxD port 122 are set to input. As a result, the transmit / receive module 123 can receive a frame 450 to be sent to bus 40 as a differential signal via its ports 121 and 122 from the communication control unit 11. In particular, if the transmit / receive module 123 sends a frame 450 to bus 40 and the TX_DM_TC signal is set, then the direction of the TxD port 121 and the direction of the RxD port 122 are set to input.

[0089] Coding block 162 generates a signal RxD2_TC from the received signal RxD_TC (RxD_TC). The RxD2_TC signal is the inverse of the RxD_TC signal. Coding block 162 outputs the RxD2_TC signal to terminal 121. If terminals 121 and 122 are configured as outputs, as previously described, the transceiver 12 can output the RxD2_TC and RxD_TC signals as a differential output signal to the communication control unit 11 via terminals 121 and 122. In the simplest case, coding block 162 is an inverter that inverts the RxD_TC signal.

[0090] The decode block 163 is connected to terminals 121 and 122 at its input. When terminals 121 and 122 are set to input, as previously described, the decode block 163 receives a differential input signal from terminals 121 and 122, consisting of a signal TxD1_TC and a signal TxD2_TC. The decode block 163 decodes the signals TxD1_TC and TxD2_TC to the non-differential signal TxD_TC. The decode block 163 outputs the signal TxD_TC to the multiplexer 154.

[0091] The transmit / receive module 123 controls the multiplexer 164 with the control signal TX_DM_TC. Depending on the signal value of the control signal TX_DM_TC, a selection is made as to whether the transmit / receive module 123 receives the signal decoded by the decode block 163 or the signal TxD1_TC from terminal 121 as signal TxD_TC.

[0092] Accordingly, the communication control unit 11, in TX-DataPhaseMode operating mode as described above, sends the bitstream of the serial transmit signal TxD as a differential signal via the TxD and RxD ports 111, 112. The transmit / receive unit 12 receives this differential signal at its TxD and RxD ports 121, 122 and decodes this differential signal to a non-differential signal TxD_TC.

[0093] Figs. 4 to 7 Figure 1 shows an example of the signal waveforms of the previously described signals in the communication control unit 11 when the subscriber station 10 is the sender of message 45 and thus the transmit / receive unit 12 is switched to TX-DataPhaseMode in data phase 453. Here, the following is shown: Fig. 6 and Fig. 7 The designation "P1" is for input and the designation "P2" is for output.

[0094] According to Figs. 4 to 7During arbitration phase 451, the communication control unit 11 and the transmit / receive unit 12 use the ports 111, 112, 121, 122 of the subscriber station 10 as usual to transmit the data. The communication control unit 11 transmits via the TxD port 111 and simultaneously receives the data from bus 40 via the RxD port 112.

[0095] In the faster operating mode of the transmit / receive device 12, the subscriber station 10 transmits exclusively as a transmitting node, as in Figs. 4 to 7 shown.

[0096] Furthermore, it is stipulated that the subscriber station 10, as a receiving node, receives exclusively in the faster operating mode of the transmit / receive device 12, as shown in Figs. 8 to 11 shown. Figs. 8 to 11Figure 1 shows an example of the signal waveforms of the previously described signals in the communication control unit 11 when the subscriber station 10 is not the sender of the message and thus the transmit / receive unit 12 is switched to RX-DataPhaseMode operating mode. This also includes... Fig. 10 and Fig. 11 The designation "P1" is for input and the designation "P2" for output. Accordingly, the transmit / receive unit 12, in RX-DataPhaseMode operating mode as described previously, sends the bitstream of the serial receive signal RxD as a differential signal via the TxD and RxD ports 121, 122. The communication control unit 11 receives this differential signal at its TxD and RxD ports 111, 112 and decodes this differential signal to the non-differential signal RxD_PRT. ​​Furthermore, the data transmission during the arbitration phase 451 and frame end phase 455 takes place via ports 111, 112, 121, 122, as previously described. Figs. 4 to 7 described.

[0097] Unlike phases 451 and 455 of a frame 450 and CAN FD, simultaneous transmission and reception on the CAN bus 40 in the RX-DataPhaseMode and TX-DataPhaseMode operating modes of the transmit / receive device 12 are no longer necessary for the subscriber stations 10 and 30 in data phase 453. During the time the transmit / receive device 12 is in an operating mode of data phase 453, the communication control unit 11 and the transmit / receive device 12 use the two terminals 111, 112, 121, 122 for the RxD and TxD signals in the same direction to transmit a differential transmit signal TxD (first operating mode of data phase 453) or a differential receive signal RxD (second operating mode of data phase 453).

[0098] According to a first modification of the aforementioned configuration of modules 15, 16, it is possible that at least one of the modules 15, 16 only allows switching to the TX-DataPhaseMode operating mode. Such a variant can be advantageous, for example, for a participant station 10, 20 of bus system 1, which itself only needs to send signals but does not need to receive any signals from bus 40 to perform its function. An example of such a participant station is a pure control element whose control is transmitted via bus 40, but which receives or generates the event for the control independently of the communication on the bus.

[0099] According to a second modification of the aforementioned configuration of modules 15, 16, it is possible for at least one of the modules 15, 16 to only allow switching to the RX-DataPhaseMode operating mode. Such a variant can be advantageous, for example, for a receiving station 10, 20 of bus system 1, which itself does not need to transmit signals, but only needs to receive signals from bus 40 to perform its function. An example of such a receiving station is an encoder, in particular a rotary encoder, actuator, etc.

[0100] Naturally, the functions of devices 11 and 12 described above can also be used for other modifications of CAN FD and / or CAN, at least for sending the user data.

[0101] As a result of the design of the subscriber station 10, no galvanic connection via an additional port on the communication control unit 11 and the associated transceiver 12 is required to ensure symmetry in data transmission between the units 11 and 12. This means that, advantageously, no additional port is needed, which is not available on a standard housing for the units 11 and 12. Therefore, switching to a different, larger, and more expensive housing to provide an additional port is unnecessary.

[0102] The described design of the device(s) 11, 12, 32, 35 enables significantly higher data rates in data phase 453 than with CAN or CAN-FD. Furthermore, the data length in the data field of data phase 453 can be freely selected, as previously described. This allows the advantages of CAN with regard to arbitration to be retained while still enabling the secure and therefore efficient transmission of a larger amount of data in a shorter time than previously possible.

[0103] Figs. 12 to 16 The signal waveforms at subscriber station 10 are shown in a second embodiment. Here, the transition between data phase 453 and frame end phase 455 is shown when subscriber station 10 is the sender of frame 450. In frame end phase 455, the transmission mode corresponds to arbitration phase 451. According to Fig. 15In the frame end phase 455, the communication control unit 11 sends data via the TxD port 111, so that port 111 is set to output (designation P2), and simultaneously receives data from bus 40 via the RxD port 112, so that port 111 is set to input (designation P1), as shown in Fig. 16 shown.

[0104] However, during the TX-DataPhaseMode operating mode in data phase 453, the communication control unit 11 uses its two terminals 111, 112 as an output (designation P2) in Fig. 15 and Fig. 16 ) and the transmit / receive device 12 uses its two terminals 121, 122 as inputs (designated P1). This results in a differential signal TxD_PRT, TxD2 being transmitted from terminals 111, 112 to terminals 121, 122 during data phase 453, which is then Fig. 13 and Fig. 14 are designated as TxD and RxD. The signal TxD according to Fig. 13 The input at pin 111 has bits with a bit duration T_B2. The signal RxD according to Fig. 14 The connection at 112 also has bits with the bit duration T_B2, since it corresponds to the inverse TxD signal.

[0105] Should the system switch from the TX-DataPhaseMode operating mode in data phase 453 to the Arbitration PhaseMode operating mode 451, in which the signals TxD, RxD are sent with a bit duration T_B1 ( Fig. 13 The operating mode switching module 15 is designed to send a non-differential signal via its two terminals 111 and 112 to signal the switching, as shown in Fig. 13 and Fig. 14 shown. For example, the operating mode switching module 15 sends the signals TxD=RxD=1 via its two terminals 111, 112 as signaling S during the switching phase 454 for a predetermined duration T, as shown in Fig. 13 and Fig. 14shown. The predetermined time duration T is at least, for example, T=100 ns. From this, the transmitting / receiving device 12 can recognize that it should now switch its operating mode to the operating mode of the arbitration phase 451.

[0106] In the previously described example, the switching signal S occurs while the CAN bus 40 is at the "Data-1" or "recessive" level. Therefore, no conflict or short circuit occurs at the RxD terminals 112 and 122 when the transceiver 12 begins driving the RxD line between the transceiver 12 and the communication control unit 11. If the switching signal S for the operating mode of the transceiver 12 is to occur at the inverse level on the CAN bus 40, the communication control unit 11 is configured to perform the switching signal S by sending the levels TxD=RxD=0.

[0107] In contrast to the switch to the frame end phase 455, in the present embodiment, the switching of operating modes from the arbitration phase 451 to the data phase 453, i.e., to one of the operating modes RX-DataPhaseMode or TX-DataPhaseMode of the transmit / receive device 12, can be signaled via the RxD port 112. For this purpose, the communication control unit 11 briefly drives the RxD port 112 more strongly than the transmit / receive device 12 drives its RxD port 122 to signal the switching of the operating mode. This prevents the value of the RxD line from being undefined if both the communication control unit 11 and the transmit / receive device 12 drive their RxD port 122, thus avoiding a superposition of the two signal sources at ports 112 and 122.In such a superposition of the two signal sources at terminals 112 and 122, the communication control unit 11 always prevails. Therefore, the value of the RxD line is always determined.

[0108] The second embodiment also has the advantage that no further connection or pin or port is necessary for the devices 11, 12, and therefore the solution is very cost-effective.

[0109] Otherwise, communication can take place in participant stations 10, 30 and in bus system 1, as described in relation to the first embodiment.

[0110] According to a third embodiment, the transceiver 12 and / or the transceiver 32, in particular the operating mode switching module 15 and / or the operating mode switching module 16, can be configured to signal something to the communication control unit 11, in particular the communication control module 113, when receiving in the RX-DataPhaseMode operating mode. For this purpose, the transceiver 12, 32 sends a non-differential signal via the TxD and RxD connections 121, 122 in an additional operating mode of the data phase 453, as described for connections 111, 112 in relation to the second embodiment. For example, the transceiver 12, 32 can send the following levels as signaling S at connections 121, 122: TxD=RxD=1.

[0111] The signaling S of the transmit-receive devices 12, 32 can contain or be additional information, which is supplementary to the information of the signals exchanged in the bus system 1 with the messages 45, 46 between subscriber stations 10, 30 of the bus system 1. The additional information enables internal communication between the devices 11, 12 or between the devices 31, 32.

[0112] Otherwise, communication can take place in participant stations 10, 30 and in bus system 1, as described in relation to the first or second embodiment.

[0113] All previously described configurations of the devices 11, 12, 31, 32, the modules 15, 16, 35, 36, the participant stations 10, 20, 30, the bus system 1 and the method carried out therein can be used individually or in all possible combinations according to the claims.

[0114] Although the invention has been previously described using the example of the CAN bus system, it can be used in any communication network and / or communication method that employs two different communication phases in which the bus states generated for these different communication phases differ. In particular, the invention is applicable to interfaces that require a switching signal from a protocol controller or module 113 for different communication phases and / or require data exchange between devices 11 and 12.

[0115] The previously described bus system 1, according to the exemplary embodiments, is based on the CAN protocol. However, the bus system 1 according to the exemplary embodiments can also be a different type of communication network in which data can be transmitted serially at two different bit rates. It is advantageous, but not a necessary requirement, that the bus system 1 ensures exclusive, collision-free access to a common channel for at least certain periods of time for each participant station 10, 20, or 30. The number and arrangement of the participant stations 10, 20, or 30 in the bus system 1 of the exemplary embodiments are arbitrary. In particular, participant station 20 can be omitted from the bus system 1. It is possible for one or more of the participant stations 10 or 30 to be present in the bus system 1.It is conceivable that all participant stations in bus system 1 are configured identically, i.e., that only participant station 10 or only participant station 30 is present.

Claims

1. Communication control device (11) for a subscriber station (10) of a serial bus system (1), having a communication control module (113) for generating a transmission signal (TxD_PRT) for controlling communication between the subscriber station (10) and at least one other subscriber station (10; 20; 30) of the bus system (1), in which bus system (1) at least a first communication phase (451, 452, 454, 455) and a second communication phase (453) are used to exchange messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1) in a frame (450) for a message (45; 46), a first connection (111) for transmitting, in an operating mode of the first communication phase (451, 452, 454, 455) of a frame (450), the transmission signal (TxD_PRT) to a transmitting / receiving device (12; 32) configured to transmit the transmission signal (TxD) to a bus (40) of the bus system (1), a second connection (122) for receiving, in the operating mode of the first communication phase (451, 452, 454, 455) of the frame (450), a digital received signal (RxD) from the transmitting / receiving device (12; 32), and an operating mode switching module (15) for switching the transmission direction of the first and second connections (111, 112) in the second communication phase (453) of the frame (450) to the same direction for differential signal transmission via the first and second connections (111, 112).

2. Communication control device (11) according to Claim 1, wherein the operating mode switching module (15) is configured so as, in a first operating mode of the second communication phase (453), to switch the first and second connections (111, 112) as an output and to use the transmission signal (TxD_PRT) to generate an inverse digital transmission signal (TxD2) and to output the transmission signal (TxD_PRT) on the first connection (111) and the inverse digital transmission signal (TxD2) on the second connection (112), and / or wherein the operating mode switching module (15) is configured so as, in a second operating mode of the second communication phase (453), to switch the first and second connections (111, 112) as an input and to use the differential received signal (RxD1, RxD2) received on the first and second connections (111, 112) to generate a non-differential received signal (RxD_PRT) and to output it to the communication control module (113).

3. Communication control device (11) according to Claim 1 or 2, wherein the operating mode switching module (15) is configured so as, in the first operating mode of the second communication phase (453), to generate and output the two transmission signals (TxD_PRT, TxD2) with the same level on the two connections (111, 112) for a predetermined period of time (T) in order to signal to the transmitting / receiving device (12) that the operating mode of the transmitting / receiving device (12) needs to be switched from the first operating mode of the second communication phase (453) to the operating mode of the first communication phase (451, 452, 454, 455).

4. Communication control device (11) according to one of the preceding claims, wherein the operating mode switching module (15) is configured to use the first or second connection (111; 112) to signal to the transmitting / receiving device (12) that the transmitting / receiving device (12) needs to switch its operating mode from the operating mode of the first communication phase (451, 452, 454, 455) to a predetermined operating mode of the second communication phase (453).

5. Communication control device (11) according to one of the preceding claims, wherein the communication control module (113) is configured to generate the transmission signal (TxD_PRT) in the first communication phase (451, 452, 454, 455) with bits having a first bit time (T_B1), which is at least a factor of 10 greater than a second bit time (T_B2) of bits that the communication control module (113) generates in the transmission signal (TxD_PRT) in the second communication phase (453).

6. Transmitting / receiving device (12; 32) for a subscriber station (10; 30) of a serial bus system (1), having a transmitting / receiving module (123) for transmitting a transmission signal (TxD_TC) to a bus (40) of the bus system (1), in which bus system (1) at least a first communication phase (451, 452, 454, 455) and a second communication phase (453) are used to exchange messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1) in a frame (450) for a message (45; 46), and for generating a digital received signal (RxD_TC) from a signal received from the bus (40), a first connection (121) for receiving, in an operating mode of the first communication phase (451, 452, 454, 455) of a frame (450), a transmission signal (TxD) from a communication control device (11; 31), a second connection (122) for transmitting, in an operating mode of the first communication phase (451, 452, 454, 455) of the frame (450), the digital received signal (RxD_TC) to the communication control device (11; 31), and an operating mode switching module (16) for switching the transmission direction of the first and second connections (121, 122) in the second communication phase (453) of the frame (450) to the same direction for differential signal transmission via the first and second connections (121, 122).

7. Transmitting / receiving device (12; 32) according to Claim 6, wherein the operating mode switching module (16; 36) is configured so as, in a first operating mode of the second communication phase (453), to switch the first and second connections (121, 122) as an input and to use the differential digital transmission signal (TxD1_TC, TxD2_TC) received on the first and second connections (121, 122) to generate a non-differential transmission signal (TxD_TC), and / or wherein the operating mode switching module (16; 36) is configured so as, in a second operating mode of the second communication phase (453), to switch the first and second connections (121, 122) as an output and to use the digital received signal (RxD_TC) to generate an inverse digital received signal (RxD2_TC) and to output the digital received signal (RxD_TC) on the second connection (122) and the inverse digital received signal (RxD2_TC) on the first connection (121).

8. Transmitting / receiving device (12; 32) according to Claim 6 or 7, wherein the operating mode switching module (16) is configured so as, in the second operating mode of the second communication phase (453), to generate and output the two received signals (RxD_TC, RxD2_TC) with the same level on the two connections (121, 122) for a predetermined period of time (T) in order to signal additional information to the communication control device (12), which is in addition to information in the signals exchanged in the bus system (1) using the messages (45; 46) between subscriber stations (10; 30) of the bus system (1).

9. Transmitting / receiving device (12; 32) according to one of Claims 6 to 8, wherein the transmitting / receiving module (123) is configured to transmit the transmission signal (TxD_TC) to the bus (40) as a differential signal (CAN_H, CAN_L).

10. Device (11; 12; 32) according to one of the preceding claims, wherein the operating mode switching module (15; 16; 36) is configured to select the transmission direction of the first and second connections (111, 112; 121, 122) according to an operating mode to which the transmitting / receiving device (12; 32) is switched.

11. Device (11; 12; 32) according to one of the preceding claims, wherein the operating mode switching module (15; 16; 35, 36) comprises a direction control block (151; 161) for controlling the transmission direction of the first and second connections (111, 112; 121, 122) on the basis of the operating mode of the transmitting / receiving device (12; 32), a coding block (152; 162) for coding the differential signals (TxD2; RxD2_TC), a decoding block (153; 163) for decoding the differential signals (TxD2; RxD2_TC) on the first and second connections (111, 112; 121, 122) into a non-differential signal (TxD_TC; RxD_PRT), and a multiplexer (154; 164) for outputting the non-differential signal (TxD_TC; RxD_PRT) generated by the decoding block (153; 163) when the transmitting / receiving device (12; 32) is switched to an operating mode of the second communication phase (453).

12. Device (11; 12; 32) according to one of the preceding claims, wherein the signal received from the bus (40) in the first communication phase (451, 452, 454, 455) is generated with a different physical layer than the signal received from the bus (40) in the second communication phase (453).

13. Device (11; 12; 31; 32) according to one of the preceding claims, wherein negotiation takes place in the first communication phase (451) in order to determine which of the subscriber stations (10, 20, 30) of the bus system (1) receives at least temporarily exclusive, collision-free access to the bus (40) in the subsequent, second communication phase (453).

14. Bus system (1), having a bus (40), and at least two subscriber stations (10; 20; 30) that are connected to one another via the bus (40) in such a way that they can communicate serially with one another and at least one subscriber station (10; 30) of which has a communication control device (11; 31) according to one of Claims 1 to 5 and 10 to 13 and a transmitting / receiving device (12; 32) according to one of Claims 6 to 13.

15. Method for communication in a serial bus system (1), wherein the method is carried out using a subscriber station (10; 30) for a bus system (1) in which at least a first communication phase (451, 452, 454, 455) and a second communication phase (453) are used to exchange messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1) in a frame (450) for a message (45; 46), wherein the subscriber station (10; 30) has a communication control device (11; 31) according to one of Claims 1 to 5 and 10 to 13 and a transmitting / receiving device (12; 32) according to one of Claims 6 to 13, and wherein the method has the steps of switching, using an operating mode switching module (15; 35) for the communication control device (11; 31), the transmission direction of the first and second connections (111, 112) for the communication control device (11; 31) in the second communication phase (453) of the frame (450) to the same direction, and switching, using an operating mode switching module (16; 36) for the transmitting / receiving device (12; 32), the transmission direction of the first and second connections (121, 122) for the transmitting / receiving device (12; 32) in the second communication phase (453) of the frame (450) to the same direction, which is different than the direction to which the first and second connections for the communication control device are switched, and performing a differential signal transmission between the communication control device (11; 31) and the transmitting / receiving device (12; 32) via the first and second connections (111, 112) for the communication control device (11; 31) and the first and second connections (121, 122) for the transmitting / receiving device (12; 32).