WO2021148348A1

WO2021148348A1 - Transmitting/receiving device for a subscriber station of a serial bus system, and method for communication in a serial bus system

Info

Publication number: WO2021148348A1
Application number: PCT/EP2021/050938
Authority: WO
Inventors: Florian Hartwich; Steffen Walker; Arthur Mutter
Original assignee: Robert Bosch Gmbh
Priority date: 2020-01-23
Filing date: 2021-01-18
Publication date: 2021-07-29
Also published as: DE102020200801A1; GB2607254A; CN115244901A; GB202212078D0

Abstract

The invention relates to a transmitting/receiving device (12;32) for a subscriber station (10; 30) of a serial bus system (1), and to a method for communication in a serial bus system (1). The transmitting/receiving device (12; 32) comprises: a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31); a transmitter (121) for transmitting the transmission signal (TxD) to a bus (40) of the bus system (1), in which bus system (1) at least one first communication phase (451, 452, 454, 454) and a second communication phase (453) are used to exchange messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1); a receiver (122) for receiving the signal from the bus (40), wherein the receiver (122) is designed to generate a digital receiver signal (RxD) from the signal received from the bus (40); a second connection for transmitting the digital receiver signal (RxD; RxD_T; RxD_R) to the communication control device (11; 31) and for receiving an operating mode switching signal (RxD_TC) from the communication control device (11; 31); and an operating mode switching block (15; 35 150) for evaluating the operation mode switching signal (RxD_TC) received by the communication device on the second connection, wherein the operating mode switching block (15; 35; 150) is designed to switch the transmitter (121) and/or the receiver (122) into one of three different operating modes according to a result of the evaluation, and the operating mode switching block (15; 35; 150) is designed to time delay a switching of the operating mode of the second communication phase (453) to the operating mode of the first communication phase (454, 455, 451, 452) up to a bit limit of a switchover phase (454) between the communication phases. Fig. 3 Nothing to translate into English

Description

description

Transmitting / receiving device for a subscriber station of a serial

Bus system and method for communication in a serial bus system

Technical area

The present invention relates to a transmitting / receiving device for a subscriber station of a serial bus system and a method for communication in a serial bus system that operates with a high data rate and great error resistance.

State of the art

A bus system is often used for communication between sensors and control units, for example in vehicles, in which data is transmitted as messages in the ISO11898-1: 2015 standard as a CAN protocol specification with CAN FD. The messages are transmitted between the bus subscribers of the bus system, such as sensor, control unit, encoder, etc., as analog signals.

Each bus subscriber in the bus system is connected to the bus with a transmitting / receiving device. At least one receiving comparator is provided in the transmitting / receiving device, which receives the analog signals from the bus and converts them into a digital signal. The content of the digital signal can be interpreted by a protocol controller. In addition, the protocol controller can create a signal for the transmission on the bus and send it to the bus with the transmitting / receiving device, so that information can be exchanged between the bus users.

In order to be able to transmit data with a higher bit rate via the bus than with CAN, the CAN FD message format and the CAN XL message format created an option to switch to a higher bit rate within a message. With such techniques, the maximum possible data rate is increased by using a higher clock rate in the area of the data fields compared to CAN. In the case of CAN FD frames or CAN FD messages, the maximum possible data rate is increased beyond a value of 1 Mbit / s. In addition, the useful data length has been extended from 8 to up to 64 bytes. The same applies to CAN XL, in which the speed of data transmission is to be increased in the range of example 10 Base-TlS Ethernet and the user data length of up to 64 bytes previously achieved with CAN FD is to be greater. As a result, the robustness of the CAN or CAN FD-based communication network can advantageously be retained.

In the course of the specification of the analog serial data transmission on the CAN bus line, transmission levels and reception thresholds for the at least one input comparator of the transmitting / receiving device (transceiver) of each subscriber station have now been set for CAN XL. The transmission level and reception thresholds have been optimized for the most flexible possible design of the bus line topology and a distinction is made in the various operating modes of the transmission / reception device (transceiver).

The disadvantage of this is that the two logical bit levels on the CAN bus line are not always clearly identified if the receiving transceiver is set to receive thresholds other than the transmit level being transmitted on the bus. This can occur in particular when a transmitting / receiving device (transceiver) is woken up from an idle state and tries to reintegrate into the ongoing communication on the bus. In order to enable such an integration of a CAN subscriber station in which the CAN subscriber station does not yet know which is the correct operating mode for the transmitting / receiving device, a third reception threshold T_OoB (Threshold Out-of-Bounds inserted, which has a value of -0.4 V, for example.

The problem, however, is that the reception threshold T_OoB can disrupt a synchronization of the subscriber stations. The reason for this is that the reception threshold T_OoB when switching back from the data phase to the Arbitration phase shifts bit edges at the connection of the transmitting / receiving device for an RxD signal, which is formed from the signal received from the bus.

Disclosure of the invention

It is therefore the object of the present invention to provide a transmitting / receiving 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 transmitting / receiving 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 the integration of a CAN subscriber station into the ongoing communication is improved.

The object is achieved by a transmitting / receiving device for a subscriber station of a serial bus system with the features of claim 1. The transmitting / receiving device has a first connection for receiving a transmission signal from a communication control device, a transmission module for transmitting the transmission signal on a bus of the bus system, in which bus system at least a first communication phase and a second communication phase are used to exchange messages between subscriber stations of the bus system , a receiving module for receiving the signal from the bus, wherein the receiving module is configured to generate a digital received signal from the signal received from the bus, a second connection for sending the digital received signal to the communication control device for receiving an operating mode switchover signal from the

Communication control device, and an operating mode switchover block for evaluating the at the second connection of the

Communication control device received mode switchover signal, wherein the mode switchover block is designed to switch the transmission module and / or the receiver module depending on a result of the evaluation in one of three different operating modes, and the mode switchover block is designed to switch the operating mode of the second communication phase in the operating mode of the first To delay the communication phase up to a bit limit of a switching phase between the communication phases.

With the transmitting / receiving device it is possible that a "false positive" is prevented in the CAN idle detection. As a result, the integration of a subscriber station into the ongoing communication on the bus can be made possible. In addition, the synchronization of the transmitting / receiving device and thus the higher-level subscriber station (CAN node) is still enabled or maintained.

In addition, an arbitration known from CAN can be retained with the transmitting / receiving device in one of the communication phases and the transmission rate can still be increased considerably compared to CAN or CAN FD. This can be achieved in that two communication phases with different bit rates are used and the beginning of the second communication phase, in which the user data is transmitted with a higher bit rate than in the arbitration, is reliably identified for the transmitting / receiving device. The transceiver can therefore safely switch from a first communication phase to the second communication phase or back. As a result, a significant increase in the bit rate and thus the transmission speed from the transmitter to the receiver can be achieved. At the same time, however, a high level of error resistance is guaranteed.

The method carried out by the transmitting / receiving device can also be used if the bus system also has at least one CAN subscriber station and / or at least one CAN FD subscriber station that send messages according to the CAN protocol and / or CAN FD protocol .

Advantageous further refinements of the transmitting / receiving device are given in the dependent claims.

The operating mode switchover block may be configured to carry out the switchover of the operating mode when switching from the second communication phase to the first communication phase, if in the received signal output by the receiving module an edge occurs between different bus states and the transmitting / receiving device is not the sender of the message.

The operating mode switchover block can be designed to switch off the transmission module in an operating mode of the second communication phase in which the transmitting / receiving device is not the sender of the message.

The operating mode switchover block may be configured to switch the operating mode when switching from the second communication phase to the first communication phase if the transceiver is the sender of the message in the second communication phase and an edge occurs between different bus states in the transmission signal.

The transmission module may be configured to drive bits of the signals onto the bus in the first communication phase with a first bit time that is at least a factor of 10 greater than a second bit time of bits that the transmission module drives onto the bus in the second communication phase. In this case, the operating mode switchover signal via the second connection for signaling the switchover of the operating mode can have at least one pulse with a pulse duration that is approximately the same as the second bit time or is shorter than the second bit time.

The communication control device can be configured to send an identifier with a predetermined value to the receiving module at the connection for the digital received signal as an operating mode switchover signal when it is necessary to switch from the first communication phase to the second communication phase.

For example, the identifier is a bit with a predetermined value or pulse pattern or the identifier is a predetermined bit pattern.

According to one option, the signal received from the bus in the first communication phase is generated with a different physical layer than the signal received from the bus in the second communication phase. It is conceivable that in the first communication phase it is negotiated which of the subscriber stations of the bus system gets an at least temporarily exclusive, collision-free access to the bus in the subsequent second communication phase.

The transmission / reception device described above and the communication control device described above can be part of a subscriber station of a bus system which also comprises a bus and at least two subscriber stations which are connected to one another via the bus in such a way that they can communicate with one another serially. In this case, at least one of the at least two subscriber stations has a transmitting / receiving device as described above.

The aforementioned object is also achieved by a method for communication in a serial bus system according to claim 13. The method is carried out with a transmitting / receiving device of a subscriber station for a bus system in which at least a first communication phase and a second communication phase are used to exchange messages between subscriber stations of the bus system, the subscriber station having a transmit module, a receive module, and an operating mode switchover block , having a first connection and a second connection, and wherein the method has the steps of receiving, with the receiving module, a signal from the bus of the bus system,

Using the receiving module, from the signal received from the bus, generating a digital received signal and outputting the digital received signal at the second connection, evaluating, with the operating mode switching block, an operating mode switching signal received by the communication control device at the second connection, and switching, with the operating mode switching block, the transmission module and / or the receiving module depending on a result of the evaluation in one of three different operating modes, the operating mode switching block switching the operating mode of the second communication phase to the operating mode of the first communication phase up to a bit limit of a switching phase delayed between the communication phases. The method offers the same advantages as mentioned above with regard to the transceiver and / or the communication control device.

Further possible implementations of the invention also include combinations, not explicitly mentioned, of features or embodiments described above or below with regard to the exemplary embodiments. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

drawings

The invention is described in more detail below with reference to the accompanying drawings and with the aid of exemplary embodiments. Show it:

1 shows a simplified block diagram of a bus system according to a first exemplary embodiment;

2 shows a diagram to illustrate the structure of messages that can be sent by subscriber stations of the bus system according to the first exemplary embodiment;

3 shows a simplified schematic block diagram of a subscriber station of the bus system according to the first exemplary embodiment;

FIG. 4 shows an electrical circuit diagram of an operating mode switchover block for switching over the operating mode of a transmitting / receiving device of the subscriber station of FIG. 3; FIG.

5 to 9 show a time profile of signals according to the first exemplary embodiment for a time phase in which a first operating mode of the transmitting / receiving device, which is switched on in the arbitration phase (first communication phase), is switched to one of two operating modes of the transmitting / receiving device. / Receiving device is switched into which the transmitting / receiving device can be switched in a data phase as a second communication phase; 10 to 15 show a time profile of signals according to the first embodiment for a time phase in which the operating mode of the transmitting / receiving device for the second communication phase, the operating mode of the transmitting / receiving device for the data phase, returns to the first operating mode the operating mode of the transmitting / receiving device for the arbitration phase is switched over;

15 to 17 show a time profile of signals at the subscriber station of FIG. 3 when the subscriber station tries to integrate itself into an ongoing communication on the bus; and

18 shows an electrical circuit diagram of an operating mode switchover block for switching the operating mode of a transmitting / receiving device of the subscriber station of FIG. 3 according to a second exemplary embodiment.

In the figures, elements that are the same or have the same function are provided with the same reference symbols, unless otherwise specified.

Description of the exemplary embodiments

As an example, FIG. 1 shows a bus system 1 which is designed in particular fundamentally for a CAN bus system, a CAN FD bus system, a CAN FD successor bus system, and / or modifications thereof, as described below. The bus system 1 can be used in a vehicle, in particular a motor vehicle, an airplane, etc., or in a hospital, etc. use.

In FIG. 1, the bus system 1 has a multiplicity of subscriber stations 10, 20, 30, each of which is connected to a bus 40 with a first bus wire 41 and a second bus wire 42. The bus wires 41, 42 can also be called CAN_H and CAN_L and are used for electrical signal transmission after coupling in the dominant level or generating recessive levels for a signal in the transmission state. Messages 45, 46 in the form of signals between the individual subscriber stations 10, 20, 30 can be transmitted serially via bus 40. The subscriber stations 10, 20, 30 are, for example, control devices, sensors, display devices, etc. of a motor vehicle. As shown in Fig. 1, the subscriber station 10 has a

Communication control device 11, a transmitting / receiving device 12 and a switching block 15. The subscriber station 20, on the other hand, has a communication control device 21 and a transmitting / receiving device 22. The subscriber station 30 has a communication control device 31, a transmitting / receiving device 32 and a switching block 35 Transmitting / receiving devices 12, 22, 32 of the subscriber stations 10, 20, 30 are each connected directly to the bus 40, even if this is not illustrated in FIG. 1.

In each subscriber station 10, 20, 30, the messages 45, 46 are encoded in the form of frames via a TXD line and an RXD line bit by bit between the respective communication control device 11, 21, 31 and the associated transmitting / receiving devices 12, 22, 32 exchanged. This is described in more detail below.

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

The communication control devices 11, 31 create and read first messages 45, which are, for example, modified CAN messages 45, which are also referred to below as CAN XL messages 45. Here, the modified CAN messages 45 or CAN XL messages 45 are structured on the basis of a CAN FD successor format, which is described in more detail with reference to FIG. 2. The communication control devices 11, 31 can also be designed to provide a CAN XL message 45 or a CAN FD message 46 for the transmitting / receiving devices 12, 32 or to receive it from them, as required. the

Communication control devices 11, 31 thus create and read a first message 45 or 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. The communication control device 21 can be designed like a conventional CAN protocol controller or 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 device 21 creates and reads second messages 46, for example Classical CAN messages or CAN FD messages 46. The CAN FD messages 46 can include a number of 0 to 64 data bytes, which also have a significantly faster data rate than a Classical CAN message. In the latter case, the communication control device 21 is designed like a conventional CAN FD controller.

The transmitting / receiving devices 12, 32 can be designed as CAN XL transceivers, apart from the differences described in more detail below. The transmitting / receiving devices 12, 32 can additionally or alternatively be designed like a conventional CAN FD transceiver. The transmitting / receiving device 22 can be designed like a conventional CAN transceiver or CAN FD transceiver.

With the two subscriber stations 10, 30, it is possible to create and then transmit messages 45 with the CAN XL format and to receive such messages 45.

FIG. 2 shows a CAN XL frame 450 for the message 45, as it is sent by the transmitting / receiving device 12 or the transmitting / receiving device 32. The CAN XL frame 450 is divided into different communication phases 451 to 455 for the CAN communication on the bus 40, namely an arbitration phase 451, a first switchover phase 452, which is at the end of the arbitration phase 451, a data phase 453, and a second switchover phase 454 , which is at the end of the data phase 453, and an end-of-frame phase 455.

In the arbitration phase 451, for example, a bit is sent at the beginning, which is also called the SOF bit and indicates the beginning of the frame or start of frame. In addition, in the arbitration phase 451, an identifier with 11 bits, for example, is sent to identify the sender of the message 45. In the case of arbitration, bit-by-bit between the Subscriber stations 10, 20, 30 negotiated which subscriber station 10, 20, 30 would like to send the message 45, 46 with the highest priority and therefore exclusive access to the bus 40 for the next time for sending in the switchover phase 452 and the subsequent data phase 453 of the bus system 1 gets.

In the present exemplary embodiment, the switchover from the arbitration phase 451 to the data phase 453 is prepared in the first switchover phase 452. In this case, protocol format information contained in at least one bit is sent, which is suitable for distinguishing CAN XL frames from CAN frames or CAN FD frames. The switchover phase 452 can have a bit ALI that has the bit duration T_B1 of a bit of the arbitration phase 451 and is sent with the physical layer of the arbitration phase 451. The physical layer corresponds to the bit transmission layer or layer 1 of the well-known OSI model (Open Systems Interconnection Model). In addition, a data length code, for example 12 bits long, can be sent, which can then assume values from 1 to 4096, in particular up to 2048, or another value with a step size of 1, or alternatively values of 0 to 4095 or higher. The data length code can alternatively comprise fewer or more bits, so that the value range and the step size can assume different values.

In the data phase 453, the user data of the CAN XL frame 450 or the message 45 are sent, which can also be referred to as the data field of the message 45. The useful data can have data in accordance with the value range of the data length code, for example with a number of up to 4096 bytes or a larger number of bytes or any other number of data. At the end of the data phase 453, for example, a checksum field can contain a checksum over the data of the data phase 453 including the stuff bits, which are inserted as an inverse bit by the sender of the message 45 after a predetermined number of identical bits, in particular 10 identical bits. In particular, the checksum is a frame checksum F_CRC with which all bits of the frame 450 up to the checksum field are secured. This can be followed by an FCP field with a predetermined value, for example 1100. In the second switchover phase 454, in the present exemplary embodiment, the switchover from the data phase 453 to the frame end phase 455 is prepared. In this case, protocol format information contained in at least one bit is sent, which is suitable for realizing the switchover. The switchover phase 454 can have a bit AH1 that has the bit duration T_B1 of a bit of the arbitration phase 451, but is sent with the physical layer of the data phase 453.

In the frame end phase 455, after two bits AL2, AH2, at least one acknowledge bit ACK can be contained in an end field in the frame end phase 455. This can be followed by a sequence of 11 identical bits, which indicate the end of the CAN XL frame 450. The at least one acknowledge bit ACK can be used to indicate whether or not a recipient has discovered an error in the received CAN XL frame 450 or message 45.

At least in the arbitration phase 451 and the frame end phase 455, a physical layer as in CAN and CAN-FD is used. In addition, in the first switchover phase 452, at least in part, that is to say at the beginning, a physical layer as with CAN and CAN-FD can be used. In addition, in the second switchover phase 454, a physical layer as with CAN and CAN-FD can be used at least partially, that is to say at the end.

An important point during phases 451, 455, at the beginning of phase 452 and at the end of phase 454 is that the known CSMA / CR method is used, which allows simultaneous access by the subscriber stations 10,

20, 30 allowed on the bus 40 without the higher priority message 45, 46 being destroyed. As a result, further bus subscriber stations 10, 20, 30 can be added to the bus system 1 relatively easily, which is very advantageous.

The consequence of the CSMA / CR method is that there must be so-called recessive states on the bus 40, which other subscriber stations 10, 20,

30 can be overwritten with dominant states on bus 40.

The arbitration at the beginning of a frame 450 or the message 45, 46 and the acknowledgment in the frame end phase 455 of the frame 450 or the Message 45, 46 is only possible if the bit time is significantly more than twice as long as the signal transit time between any two subscriber stations 10, 20, 30 of the bus system 1. The bit rate is therefore in the arbitration phase

451, the frame end phase 455 and at least partially in the switching phases

452, 454 is selected to be slower than in the data phase 453 of the frame 450. In particular, the bit rate in the phases 451, 452, 454, 455 is selected as 500 kbit / s, which results in a bit time of approx. 2ps, whereas the bit rate in the data phase 453 is selected as 5 to 10 Mbit / s or more, from which a bit time of approx. 0, lps and less follows. The bit time of the signal in the other communication phases 451, 452, 454, 455 is thus at least a factor of 10 greater than the bit time of the signal in the data phase 453.

A sender of the message 45, for example the subscriber station 10, does not begin sending bits of the switchover phase 452 and the subsequent data phase 453 on the bus 40 until the subscriber station 10 as the sender has won the arbitration and the subscriber station 10 as the sender is ready to send has exclusive access to bus 40 of bus system 1. The transmitter can either switch to the faster bit rate and / or the other physical layer after part of the switchover phase 452 or switch to the faster bit rate and / or the other physical layer only with the first bit, i.e. at the beginning of the subsequent data phase 453 .

In general, the following properties that differ from CAN or CAN FD can be implemented in the bus system with CAN XL: a) Adoption and, if necessary, adaptation of proven properties that are responsible for the robustness and user-friendliness of CAN and CAN FD, in particular the frame structure Identifier and arbitration according to the CSMA / CR method, b) increase the net data transmission rate to around 10 megabits per second, and c) increase the size of the user data per frame to around 4kbytes or any other value.

3 shows the basic structure of the subscriber station 10 with the communication control device 11, the transmitting / receiving device 12 and the switchover block 15. The subscriber station 30 is similar constructed as shown in FIG. 3, except that the block 35 is provided separately from the communication control device 31 and the transceiver 32. The subscriber station 30 and the block 35 are therefore not described separately. The functions of the switchover block 15 described below are identical in the switchover block 35.

According to FIG. 3, the communication control device 11 also has a communication control module 111, a transmission signal output driver 112 and an RxD connection configuration module 113. The

Communication control device 11 is designed as a microcontroller or has a microcontroller. The communication control device 11 processes signals from any application, for example a control device for an engine, a safety system for a machine or a vehicle, or other applications.

However, not shown in FIG. 3 is a system ASIC (ASIC = application-specific integrated circuit), which can alternatively be a system base chip (SBC) on which several functions necessary for an electronic assembly of the subscriber station 10 are combined. Among other things, the transmitting / receiving device 12 and an energy supply device (not shown) which supplies the transmitting / receiving device 12 with electrical energy can be installed in the system ASIC. The energy supply device usually supplies a voltage CAN_Supply of 5 V. Depending on requirements, however, the energy supply device can supply a different voltage with a different value and / or be designed as a current source.

According to FIG. 3, the transmission / reception device 12 also has a transmission module 121, a reception module 122, a driver 123 for the transmission signal TxD, a reception signal output driver 124 and a driver 125 which outputs a signal RxD_TC to the switchover block 15. The switching block 15 forms an operating state switching signal S_OP for switching the transmission module 121 and / or the receiving module 122 from the signal RxD_TC and a signal S_SW, which is the output signal of the receiving module 122. In addition, the switching block 15 forms the signal S_OP and the signals TxD, S_SW an operating state switching signal S_OPT for switching reception thresholds of the Receiving module 122. The switching signal S_OP can contain the switching signal for the sending module 121 and the receiving module 122 in one bit, for example. Alternatively, the switching signal S_OP can be a two-bit-wide signal in order to control transmission module 121 and reception module 122 separately, for example by providing the first bit for switching the transmission module 121 and the second bit for switching the reception module 122. Of course, any alternative options for the configuration of the switching signal S_OP are conceivable. The transmission module 121 is also referred to as a transmitter. The receiving module 122 is also referred to as a receiver.

The switchover block 15 can be designed as a switch block which, in particular, has at least one flip-flop. This is described in more detail below with reference to FIGS. 4 to 14.

Even if the transmitting / receiving device 12 is always referred to below, it is alternatively possible to provide the receiving module 122 in a separate device external to the transmitting module 121. The transmission module 121 and the reception module 122 can be constructed in the same way as in a conventional transmission / reception device 22. The transmission module 121 can in particular have at least one operational amplifier and / or one transistor. The receiving module 122 can in particular have at least one operational amplifier and / or one transistor.

As shown in FIG. 3, the transmitting / receiving device 12 is connected to the bus 40, more precisely its first bus core 41 for CAN_H and its second bus core 42 for CAN_L. The first and second bus wires 41, 42 are connected in the transmitting / receiving device 12 to the transmitting module 121 and to the receiving module 122. The voltage supply for the energy supply device for supplying the first and second bus wires 41, 42 with electrical energy takes place as usual. In addition, the connection to ground or CAN_GND is implemented as usual. The same applies to the termination of the first and second bus wires 41, 42 with a terminating resistor. The switchover block 15 is designed to recognize the beginning of the respective switchover phases 452, 454 in a received message 45 from the bus 40 and then to switch over the properties of the transmitting / receiving device 12.

The switchover block 15 can switch between the following operating modes of the transmitting / receiving device 12: a) first operating mode: transmit / receive properties for the arbitration phase 451, b) second operating mode: transmit / receive properties for the data phase 453 as a transmitter (transmit node), Transmitting / receiving device 12 acts as a sender and thus also a receiver of the message 45 or a frame 450, c) third operating mode: transmitting / receiving properties for the data phase 453 as a receiver (receiving node), transmitting / receiving device 12 is not a transmitter, but acts only as the recipient of the message 45 or a frame 450.

The RxD connection configuration module 113 configures the connection RxD depending on the required communication direction using signals S1, S2 at its input, as described below. The signal S1 can be referred to as RxD_out_ena, which does not enable the additional signal RxD_TC to be driven via the RxD connection (first connection operating mode) or the additional signal RxD_TC to be driven via the RxD connection (second connection operating mode). The signal S2 can be referred to as RxD_out_val. Depending on the value of the signal S2, the communication control device 11 drives the connection RxD at the switching times between the two different communication phases to signal the operating mode to be set to the transmitting / receiving device 12, i.e. on the one hand in the first switching phase 452 for switching between the arbitration phase 451 and data phase 453 and on the other hand in the second switching phase 454 for switching between data phase 453 and frame end phase 455. Optionally, depending on the value of signal S2, communication control device 11 can drive connection RxD in a third connection operating mode, also called “talk mode” can, in which internal communication between the devices 11, 12 is possible. Otherwise, the connection RxD, as is common in CAN in particular, is an input for the communication control device 11, that is to say not an output, as described above, so that the communication control device 11 does not drive the connection RxD. the Connection RxD can thus be operated bidirectionally with the aid of the RxD connection configuration module 113 and the signals S1, S2. In other words, the port RxD is a bidirectional port.

For this purpose, the communication control device 11 and the output driver 124 are designed in such a way that the communication control device 11 drives the connection RxD more strongly than the output driver 124 when driving for the purpose of signaling Communication control device 11 and output driver 124 drives connection RxD and the two signal sources are superimposed at connection RxD. With such a superposition of the two signal sources at the connection RxD, the communication control device 11 always prevails. This always determines the value of the RxD line.

The switchover block 15 can thus provide the option of signaling the setting of one of the three previously mentioned operating modes in the transmitting / receiving device 12 via the RxD connection, which modes form different operating states of the transmitting / receiving device 12. An additional connection to the transmitting / receiving device 12 and thus also to the communication control device 11 is not required for this.

For this purpose, the switchover block 15 is provided with the three inputs according to FIG. 3, via which a signal RxD_TC, the signal TxD and the signal S_SW are fed into the switchover block 15. The signal RxD_TC is based on a signal which is sent from the communication control device 11 to the transmitting / receiving device 12 via the connection for the RxD signal. With the RxD_TC signal, the communication control device 11 signals to the transceiver device 12 on the one hand that the transceiver device 12 now has to switch to the operating mode for the data phase 453. At the end of the data phase 453, the communication control device

11 with the signal RxD_TC the switchover of the transmitting / receiving device

12 from the operating mode of the data phase 453 to the operating mode for the arbitration phase 451. In addition, any other information can be sent from the communication control device 11 to the transceiver device 12 with the signal RxD_TC, as mentioned above. According to FIG. 3, the transmitting / receiving device 12 carries the signal RxD_TC from the connection RxD via the driver 125 to the connection of the switchover block 15 for the signal RxD_TC. The signal S_SW, on the other hand, is generated from the signal received from bus 40. The signal RxD_TC is passed between the connection for the RxD signal and the output of the receive signal driver 124 to the switchover block 15. The signal S_SW is passed from the output of the receiving module 122 and before the input of the receiving signal driver 124 to the switchover block 15.

According to a specific example shown in FIG. 4, the switching block 15 has two D flip-flops 151, 152, into which the signal RxD_TC is input as a clock signal. The two D flip-flops 151, 152 respond to rising clock edges of the clock signal, that is to say of the signal RxD_TC. A high state or a first binary signal state is also present at the input of the D flip-flop 151 with the signal S_H. In addition, the inverted signal S_SW is input to the D flip-flops 151, 152 as a reset. The signal S_SW is passed via an inverter 155 before being input to D flip-flops 151, 152. The D flip-flops 151, 152 are connected to logic gates 156, 157, namely an AND gate 156 and an OR gate 157. The output of the OR gate

157 is fed as a clock signal to a D flip-flop 158, into which a time-out signal S_TO is also fed as a reset, which indicates the expiry of a predetermined time period TO. The signal S_TO becomes active if no edges are detected on the bus 40 for a predetermined time period TO, for example 11 bit times. The D flip-flop 158 responds to rising clock edges. In addition, an inverter 159 is connected between the D flip-flop 158 and an input of the AND gate 156. In the specific example of FIG. 4, while the signal S_SW is high, the third D flip-flop 158 is switched from 0 to 1 by two falling edges of the signal RxD_TC. When the flip-flop

158 is 1, while the S_SW signal is high, it is switched from 1 to 0 by a falling edge of the RxD_TC signal. When the signal S_SW is low, the two D flip-flops 151, 152 are reset and do not respond to rising edges of the signal RxD_TC.

With the help of a block 160, the transceiver 12 can initially do the transition from the data phase 453 to the frame end phase 455 Store toggle signal RxD_TC, which contains at least one high pulse driven by communication control device 11. This is described in more detail below with reference to FIGS. 5 to 14.

The switching conditions described above can of course be defined differently, for example rising edges on the RxD_TC signal while the S_SW signal is low. In addition, other levels and / or other numbers of edges are possible with other circuits in switchover block 15.

In the specific example of FIG. 4, the D flip-flop 158 drives the binary operating state switching signal S_OP. If the switching signal S_OP is to be two bits wide, or if more than two operating states are to be displayed, additional D flip-flops with different switching conditions than described above are required.

If the switchover block 15 detects the switchover phase 452, the signal S_OP output from the switchover block 15 is used to switch the operating state of the transmitter module 121 and / or the receiver module 122 and thus the operating mode of the transmitter / receiver device 12. This is explained in more detail with reference to FIGS. 5 to 9.

When the bus system 1 is in operation, the transmission module 121, when the subscriber station 10 acts as a transmitter, converts a transmission signal TxD of the communication control device 11 into corresponding signals CAN_H and CAN_L for the bus wires 41, 42 and sends these signals CAN_H and CAN_L to the bus 40, such as 5 for the transition from arbitration phase 451 with switchover phase 452 to data phase 453. A bit duration T_B1 of the arbitration phase 451 is switched to a shorter bit duration T_B2 of the data phase 453. Even if the signals CAN_H and CAN_L are mentioned here for the transmitting / receiving device 12, these are to be understood in relation to the message 45 as signals CAN-XL_H and CAN-XL_L, which in the data phase 453 of the conventional signals CAN_H and CAN_L differ in at least one feature, in particular with regard to the formation of the bus states for the various data states of the signal TxD and / or with regard to the voltage or the physical layer and / or the bit rate. In the example of FIG. 5, the signals CAN-XL_H and CAN-XL_L deviate in the data phase 453 with regard to the formation of the bus states for the various data states of the signal TxD and with regard to the voltage or the physical layer and the bit rate the conventional signals CAN_H and CAN_L in phases 451, 452.

As shown in FIG. 6, a differential signal VDIFF = CAN_H - CAN_L is formed as a result of the signals on bus 40. With the exception of an idle or standby state, the transmitting / receiving device 12 with the receiving module 122 always listens to a transmission of data or messages 45, 46 on the bus 40 in normal operation, regardless of whether the subscriber station 10 The sender of the message 45 is or is not. Here, the receiving module 122 uses a receiving threshold T_a in the arbitration phase 451 and at the beginning of the switchover phase 452. At the end of the switchover phase 452 and in the data phase 453, the receiving module 122 exclusively uses a receiving threshold T_d which is between 0V and +/- 0.1V. The minimum value for a differential voltage of a bus state DO in the data phase 453, which is designated as VDIFF_D0_Min, lies in the lower range for the reception threshold T_a. The receiving module 122 forms a signal S_SW and forwards this via the received signal output driver 124 as a digital received signal RxD to the communication control device 11, as shown in FIG. 3. If the transmitting / receiving device 12 is switched to the operating mode for the arbitration phase 451, the device 12 cannot reliably recognize the “0” bits of the data phase 453 because the current switching threshold or reception threshold T_a is in its lower tolerance range and thus below it of VDIFF_D0_Min could be.

FIG. 7 shows part of the transmission signal TxD, which is transmitted, for example, from the subscriber station 10 to the bus 40. With a delay time T_TLD that occurs during operation, which is also referred to as transmitter loop delay, the subscriber station 10 receives a signal as a transmitter and uses it to form a digital received signal RxD_T with the receiving module 122 and the driver 124, as shown in FIG. 8. The delay time T_TLD depends on the temperature, operating voltage and production tolerances and is usually in the data sheet of the transmission / Receiving device 12 specified specified in a tolerance range. In the ideal case, there is no delay period T_TLD.

According to FIGS. 5 to 7, the communication control device 11 sends an FDF bit and an XLF bit, each with the high state (first binary signal state), one after the other in the transmit signal TxD before the switchover phase 452. This is followed by a resXL bit that is sent with the low state (second binary signal state) and is followed by an ALl bit that is sent with the low state (second binary signal state). Thereafter, at the end of the arbitration phase 451, on the basis of a signal RxD_TC, which is shown in FIG. 8 and has a pulse duration T_B3, from the bits of the arbitration phase 451 with the bit time T_B1 to the bit level and switching threshold (s) of the data phase 453 and with the bit time T_B2 is switched as shown in Figs. The pulse duration T_B3 is approximately the same or shorter or shorter than the bit time T_B2.

In particular, the pulse duration T_B3 is equal to the bit time T_B2. The pulse duration T_B3 is smaller or shorter than the bit time T_B1. After the ALl bit, bits DH1, DL1 of data phase 453 follow and then the user data. The signal RxD_TC only switches the analog components 121, 122 of the transmitting / receiving device 12. The lengths of the bit times T_B1, T_B2 are only switched within the digital communication control device 11.

According to FIG. 9, the subscriber station 30, which is only the receiver of the signal from the bus 40, for example, receives the signal from the bus 40 with an additional delay period T_BLD, which is also referred to as the bus line delay. The subscriber station 30 forms a digital received signal RxD_R therefrom, as shown in FIG. 9. The received signal RxD_R is therefore additionally delayed by the delay period T_BLD compared to the received signal RxD_T.

According to FIG. 8, the transmitting / receiving device 12 of the subscriber station 10 sees a received signal RxD_T, which differs from the previously described course of the TxD signal of FIG. 7, in the ALl bit, which has the second binary signal state (low). has two high pulses AL_2. In other words, the communication control device 11 sends a signal RxD_TC via the RxD connection, in which the AL bit contains a Identifier in the form of two pulses AL_2 with the first binary signal state (high), i.e. with the inverse signal state, can be sent. This signals to the transmitting / receiving device 12 that it is necessary to switch from its first operating mode to its second operating mode in order to generate the bus signal CAN_H, CAN_L from the following bits of the transmit signal TxD. The signal RxD_TC causes the switchover with the switchover block 15 at the edge S_TD. In the second operating mode, the subscriber station 10 acts as a transmitter and as a receiver of the message 45 or of the frame 450.

According to FIG. 9, on the other hand, the transmitting / receiving device 32 of the subscriber station 30 sees a received signal RxD_R which has a high pulse AL_1 in the AL1 bit, in contrast to the previously described course of the TxD signal of FIG. 7. In other words, the communication control device 31 sends a signal RxD_TC via its RxD connection, in which an identifier in the form of a pulse AL_1 with the first binary signal state, (high), i.e. with the inverse signal state, is sent in the AL bit . This signals to the transmitting / receiving device 32 that it is necessary to switch from its first operating mode to its third operating mode. The signal RxD_TC causes the switchover with the switchover block 15 at the edge S_RD. In the third operating mode, the subscriber station 30 only acts as a recipient of the frame 450, that is, the subscriber station 30 has lost the previous arbitration or is currently not sending a message 45.

The signaling can thus take place in such a way that a sequence of two high pulses AL_2 indicates the transition from the arbitration phase 451 (first operating mode) to the data phase 452 as a transmitter (second operating mode), as shown in FIG. 8, and that a high Pulse AL_1 indicates the transition from the arbitration phase 451 (first operating mode) to the data phase 452 as a receiver (third operating mode), as shown in FIG. 9. Thereafter, the transmission of the data of the data field 453 of a frame 450 can be carried out.

When the operating mode of the transmitting / receiving device 12 changes from the first operating mode (arbitration) to the second or third operating mode, the time delay of the block 160 is set to the value zero. The receiving module 122 thus switches its receiving threshold T_a to the arbitration phase 451 the reception threshold T_d of the data phase 453 immediately. If the transmitter / receiver device 12 is to be switched to the second operating mode, that is, if the transmitter / receiver device 12 acts as the transmitter of the frame 450, the transmitter module 121 switches when the transmission signal TxD switches to low (second signal state). Of course, other switching conditions are also conceivable.

As can be seen from FIGS. 10 to 14, the transceiver 12 proceeds as follows during the transition from the data phase 453 to the frame end phase 455. With the aid of block 160, the transmitting / receiving device 12 initially stores the switchover signal RxD_TC, which contains a low pulse driven by the communication control device 12, as shown in FIG. 13. The block 160 then waits for an edge on the TxD signal according to FIG. 12 and then simultaneously switches its transmission module 122 and the reception threshold of its reception module from the reception threshold T_d of the data phase 453 to the reception threshold T_a for the arbitration, i.e. the switching thresholds of their reception comparator . In addition, the transmitting / receiving device 12 switches on a receiving threshold T_OoB (Threshold Out-of-Bounds) for its receiving comparator in the receiving module.

In contrast, the transceiver 32, which in the example shown is only the receiver of the frame 450, proceeds during the transition from the data phase 453, as can be seen from FIGS. 11 and 14. The transmitting / receiving device 32 waits for an edge S_TH on the bus 40, i.e. an edge of the signal S_SW, and only then switches the reception threshold of its reception module from the reception threshold T_d of the data phase 453 to the reception threshold T_a for the arbitration, i.e. the switching thresholds of its Receiving comparator. In addition, the transmitting / receiving device 32 switches on a receiving threshold T_OoB (Threshold Out-of-Bounds) for its receiving comparator in the receiving module.

In other words, if the communication control device 12, 32 signals its associated transmitting / receiving device 12, 32 to switch the operating mode of the transmitting / receiving device 12, 32, the transmitting / receiving device 12, 32 delays the switching until the transmitting / receiving device 12, 32 / Receiving device 12, 32 recognizes a bit limit. The broadcast

/ Receiving device 12 in the transmitter recognizes the bit limit on an edge on the TxD input pin. The transmitting / receiving device 12,

32 in the receiver, which is not a sender of the frame 450, recognizes the bit boundary on an edge on the CAN bus 40.

This prevents the reception threshold T_OoB from interfering with the switching back of the transmitting / receiving device 12 from the data phase 453 to the operating mode of the arbitration phase 455, 451 by shifting the second edge of the AHl bit at the RxD connection. As a result, the synchronization of the subscriber stations 10, 20, 30 of the bus system 1 is not disturbed, which would otherwise be shifted by shifting the second edge of the AH1 bit at the RxD connection.

The reception threshold T_OoB can thus be used when integrating a subscriber station 10, 20, 30 into an ongoing communication, as shown in FIGS. 15 to 17. To this end, the subscriber station 10, 20, 30 searches for an uninterrupted sequence of 11 recessive bits, that is, RxD = 1 or RxD_R = 1 or RxD_T = 1. The bus is then recognized as idle, i.e. in the idle state. This sequence of 11 recessive bits occurs between the dominant ACK bit of one CAN frame 450 and the start bit SOF of the following CAN frame 450 or even if no frames 450 are sent at all.

In the example of FIGS. 15 to 17, after the transmission of phases 451, 452, communication on bus 40 goes into data phase 453. The subscriber station that was switched on initially only acts as a receiver and generates signal RxD in the process Received signal RxD_R as shown in FIG. The subscriber station is, for example, the subscriber station 10. In the subscriber station 10, the transmitting / receiving device 12 is thus initially switched to the operating mode for the arbitration phase 451 after being switched on. The reception thresholds T_a, T_OoB are switched on in the reception module 122, as illustrated in FIG. 16. The reception threshold T_OoB (Threshold Out-of-Bounds) has become necessary because the reception threshold T_a of the arbitration phase 451 cannot reliably recognize the logical "0" bits in the data phase 453. The reason for this is that the reception threshold T_a, depending on manufacturing tolerances, temperature and operating voltage, is in the range of 0.5V up to 0.9V, as specified in ISO 11898-2. If the differential voltage VDIFF is higher, RxD = '0' = dominant. If the differential voltage VDIFF is below this, RxD = = recessive. If the differential voltage VDIFF is in the range mentioned, RxD is indefinite. A logical '0' should be sent in data phase 453 as VDIFF = IV. If this voltage is weakened to VDIFF = 0.8V via the bus line at the receiving subscriber stations (receiving nodes), this voltage VDIFF cannot be reliably identified with the reception threshold T_a.

According to FIG. 17, the subscriber station 10 forms the received signal RxD_R from the signals received from the bus 40 according to FIG. 15 and FIG. 16 on the basis of the reception thresholds T_a and T_OoB. States DA_R whose voltage values U for the differential voltage VDIFF = CAN_H-CAN_L are not above the upper limit of the tolerance range defined for the reception threshold T_a are recognized as recessive, for example. In contrast, states D_D, the differential voltage of which is below the reception threshold T_OoB, are recognized as dominant. This also applies to the state D_D, which is present at time t1. The value for the threshold T_a is in the range from 0.5V to 0.9V due to the tolerances described above.

The reception threshold T_OoB causes the 1‘ bits in the data phase 453 to be output as 0‘ bits and compensates for 0‘ bits that were not recognized if their differential voltage VDIFF is weakened in the unsafe area of T_a. The reception threshold T_OoB thus prevents such a subscriber station from mistakenly recognizing a sequence of data bits as the idle state of the bus 40 and therefore assumes that the CAN bus 40 is free and therefore starts its own frame that interferes with the frame that has already been sent.

Due to the design of the subscriber station 10 described above, no galvanic connection is required through an additional connection to the communication control device 11 and the associated transmitting / receiving device 12 so that the communication control device 11 can send the time of the bit level and switching threshold switchover or other data to the Transmitting / receiving device 12 can transmit. That is, the block 15 needs advantageously no additional connection that is not available on a standard housing of the transmitter / receiver device 12. As a result of the block 15, it is therefore not necessary to change to another, larger and more expensive housing in order to provide an additional connection.

In addition, the operating mode switchover block 15 enables the transceiver device 12 not to require any protocol controller functionality. Such a protocol controller could, among other things, recognize the switchover phase 452 of the message 45 and, depending on this, initiate the data phase 453. However, since such an additional protocol controller would require a considerable amount of space in the transmitting / receiving device 12 or the ASIC, the operating mode switchover block 15 brings about a significant reduction in the resource requirement.

As a result, the interconnection of the operating mode switchover block 15 with a conventional transmitter / receiver device offers a very inexpensive and inexpensive solution for making the transmitter / receiver device 12 know that a switchover and which switchover is to be made between its various operating modes, namely in particular from the first operating mode to the second operating mode or from the first operating mode to the third operating mode or from the second operating mode to the first operating mode or some other switchover of operating modes.

As a result of the described configuration of the transmitting / receiving device (s) 12, 32, much higher data rates can be achieved in the data phase 452 than with CAN or CAN-FD. In addition, the data length in the data field of the data phase 453 can be selected as desired, as described above. As a result, the advantages of CAN in terms of arbitration can be retained and a larger number of data can still be transmitted very securely and thus effectively in a shorter time than before, i.e. without the need to repeat the data due to an error, as explained below .

Another advantage is that error frames are not required in the bus system 1 for the transmission of messages 45, but can be used optionally. If error frames are not used, messages 45 are no longer destroyed, which eliminates one cause of the need for double transmission of messages. This increases the net data rate. If the bus system is not a CAN bus system, the operating mode switchover block 15, 35 can be designed or be able to react to other switchover signals. In this case, the operating mode switching block 15, 35 can switch the transmission module 121 and / or the receiving module 122 to one of at least two different operating modes and at least one of the operating modes after one of the operating mode switching blocks 15, 35 has elapsed, depending on a result of its evaluation switch to another of the operating modes for the preset time period TO.

18 shows a variant for a switchover block 150 which, according to a second exemplary embodiment, can be used in a subscriber station 10 instead of the switchover block 15.

In contrast to the previous exemplary embodiment, the switchover block 150 uses the S_OP signal as an input instead of the RxD_TC signal. The advantages of the preceding exemplary embodiment can also be achieved in this way.

Otherwise, the bus system 1 in the second exemplary embodiment is constructed in the same way as described above with reference to the first exemplary embodiment.

All of the above-described configurations of blocks 15, 35, 150, subscriber stations 10, 20, 30, bus system 1 and the method carried out therein can be used individually or in all possible combinations. In particular, all the features of the exemplary embodiments described above and / or their modifications can be combined as desired. In addition or as an alternative, the following modifications in particular are conceivable.

Even if the invention is described above using the example of the CAN bus system, the invention can be used in any communication network and / or communication method in which two different communication phases are used in which the bus states that are generated for the different communication phases differ. In particular, the invention is useful for developments of others serial communication networks such as Ethernet and / or 10 Base-TlS Ethernet, field bus systems, etc. can be used.

The above-described bus system 1 according to the exemplary embodiments is described using a bus system based on the CAN protocol. That

Bus system 1 according to the exemplary embodiments can, however, 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 mandatory prerequisite, that in the bus system 1, at least for certain periods of time, an exclusive, collision-free access of a

Subscriber station 10, 20, 30 is guaranteed on a common channel.

The number and arrangement of the subscriber stations 10, 20, 30 in the bus system 1 of the exemplary embodiments is arbitrary. In particular, the subscriber station 20 in the bus system 1 can be omitted. It is possible for one or more of the subscriber stations 10 or 30 to be present in the bus system 1. It is conceivable that all subscriber stations in the bus system 1 are configured identically, that is to say only subscriber station 10 or only subscriber station 30 are present.

Claims

Expectations

1) Transmit / receive device (12; 32) for a subscriber station (10; 30) of a serial bus system (1), with a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31), a transmission module (121 ) for sending the transmission signal (TxD) on a bus (40) of the bus system (1), in which bus system (1) for exchanging messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1) at least a first communication phase (451, 452, 454, 455) and a second communication phase (453) are used, a receiving module (122) for receiving the signal from the bus (40), the receiving module (122) being designed from that of the bus (40) received signal to generate a digital reception signal (RxD; RxD_T; RxD_R), a second connection for sending the digital reception signal (RxD; RxD_T; RxD_R) to the communication control device (11; 31) and for receiving an operating mode switchover signal (RxD_TC) from the communicat ion control device (11; 31), and an operating mode switchover block (15; 35; 150) for evaluating the at the second connection of the

Communication control device (11; 31) received mode switchover signal (RxD_TC), the mode switchover block (15; 35; 150) being configured, the transmission module (121) and / or the reception module (122) depending on a result of the evaluation in a to switch from three different operating modes, and wherein the operating mode switching block (15; 35; 150) is designed to switch the operating mode of the second communication phase (453) to the operating mode of the first communication phase (454, 455, 451, 452) up to a bit limit of a switching phase (454) between the communication phases.

2) Transmitting / receiving device (12; 32) according to claim 1, wherein the operating mode switchover block (15; 35) is designed when switching from the second communication phase (453) to the first communication phase (454, 455, 451, 452) ) to switch over the operating mode if an edge occurs between different bus states in the received signal (S_SW) output by the receiving module (122) and the transmitting / receiving device (12; 32) is not the sender of the message (45).

3) transmitting / receiving device (12; 32) according to claim 1 or 2, wherein the operating mode switchover block (15; 35) is designed to switch off the transmitting module (121) in an operating mode of the second communication phase (453) in which the transmission - / receiving device (12; 32) is not the sender of the message (45).

4) transmitting / receiving device (12; 32) according to claim 1 or 2, wherein the operating mode switchover block (15; 35) is designed when switching from the second communication phase (453) to the first communication phase (454, 455, 451) , 452) to switch the operating mode when the transceiver (12; 32) is the sender of the message (45) in the second communication phase (453) and an edge occurs between different bus states in the transmit signal (TxD).

5) Transmit / receive device (12; 32) according to one of the preceding claims, wherein the transmission module (121) is designed to send bits of the signals to the bus (40) with a first bit time (T_B1) in the first communication phase (451) drive that is at least a factor of 10 greater than a second bit time (T_B2) of bits that the transmission module (121) drives on the bus (40) in the second communication phase (453). 6) transmitting / receiving device (12; 32) according to claim 5, wherein the operating mode switching signal (RxD_TC) via the second connection for signaling the switching of the operating mode has at least one pulse with a pulse duration (T_B3) that is approximately equal to the second Bit time (T_B2) is or shorter than the second bit time (T_B2).

7) Transmitting / receiving device (12; 32) according to one of the preceding claims, wherein the communication control device (11; 31) is designed to have an identifier (AL_1; AL_1; AL_2) to be sent with a predetermined value to the receiving module (122) when it is necessary to switch from the first communication phase (451, 452) to the second communication phase (453).

8) transmitting / receiving device (12; 32) according to claim 7, wherein the identifier (AH_2; AH_3) is a bit with a predetermined value or pulse pattern.

9) transmitting / receiving device (12; 32) according to claim 7, wherein the identifier (AH_2; AH_3) is a predetermined bit pattern.

10) transmitting / receiving device (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 that in of the second communication phase (453) received from the bus (40).

11) transmitting / receiving device (12; 32) according to one of the preceding claims, wherein in the first communication phase (451, 452, 454, 455) it is negotiated which of the subscriber stations (10, 20, 30) of the bus system (1) in the subsequent second communication phase (453) receives an at least temporarily exclusive, collision-free access to the bus (40).

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

13) Method for communication in a serial bus system (1), the method being carried out with a transmitting / receiving device for a subscriber station (10; 30) of a bus system (1), in which for the exchange of messages (45; 46) between Subscriber stations (10, 20, 30) of the bus system (1) at least a first communication phase (451, 452, 454, 455) and a second communication phase (453) are used, the subscriber station (10; 30) having a transmission module (121), a receiving module (122), an operating mode switchover block (15; 35), a first connection and a second connection, and wherein the method comprises the steps of,

Receiving, with the receiving module (122), a signal from the bus (40) of the bus system (1),

Using the receiving module (122) to generate a digital received signal (RxD; RxD_T; RxD_R) from the signal received from the bus (40) and output the digital received signal (RxD; RxD_T; RxD_R) to the second connection,

Evaluate, with the operating mode switchover block (15; 35; 150), one at the second connection of the

Communication control device (11; 31) received operating mode switchover signal (RxD_TC), and

Switching with the operating mode switching block (15; 35), the transmission module (121) and / or the receiving module (122) depending on a result of the evaluation in one of three different operating modes, the operating mode switching block (15; 35; 150 ) a switchover of the operating mode of the second communication phase (453) to the operating mode of the first communication phase (454, 455, 451, 452) is delayed up to a bit limit of a switching phase (454) between the communication phases.