CN115244901B - Transmitting/receiving device and method for communication in serial bus system - Google Patents

Abstract

A transmitting/receiving device (12; 32) for a subscriber station (10; 30) of a serial bus system (1) and a method for communication in a serial bus system (1) are provided. The transmitting/receiving device (12; 32) has: a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31); -a transmission module (121) for transmitting the transmission signal (TxD) onto a bus (40) of the bus system (1), for which bus system (1) at least one first communication phase (451, 452, 454, 455) and one second communication phase (453) are used for exchanging messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1); -a receiving module (122) for receiving signals from the bus (40), wherein the receiving module (122) is designed for generating a digital received signal (RxD; rxd_t; rxd_r) from the signals received from the bus (40); a second connection for transmitting the digital received signal (RxD; rxD_T; rxR_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 operation mode switching block (15; 35; 150) for evaluating an operation mode switching signal (RxD_TC) received at the second junction from the communication control device (11; 31), wherein the operation mode switching block (15; 35; 150) is designed for switching the transmitting module (121) and/or the receiving module (122) into one of three different operation modes depending on the result of the evaluation, and wherein the operation mode switching block (15; 35; 150) is designed for delaying the switching of the operation mode of the second communication phase (453) into the operation mode of the first communication phase (454, 455, 451, 452) in time until a bit boundary of a switching phase (454) between the communication phases.

Description

Transmitting/receiving device and method for communication in serial bus system

Technical Field

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 which operates with high data rates and large error robustness.

Background

For communication between, for example, sensors and control devices in a vehicle, a bus system is generally used, in which data is used as messages in ISO 11898-1: the 2015 standard is transmitted with CAN FD as CAN protocol specification. Messages are transmitted as analog signals between bus users of the bus system, such as sensors, control devices, transmitters, etc.

Each bus user of the bus system connects to the bus with a transmitting/receiving device. At least one receiving comparator is provided in the transmitting/receiving device, which receives the analog signal from the bus and converts it 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 transmission on the bus and transmit the signal onto the bus with the transmitting/receiving device, so that information can be exchanged between bus users.

In order to be able to transmit data via the bus at a higher bit rate than in the case of CAN, an option is provided in the CAN FD message format and in the CAN XL message format for conversion to a higher bit rate within the message. In such a technique, the maximum possible data rate is increased by using a higher clock pulse than CAN in the region of the data field. Here, the maximum possible data rate is increased to a value exceeding 1MBit/s for CAN FD frames or CAN FD messages. Further, the effective data length extends from 8 bytes to 64 bytes. The same applies to CAN XL, for which the speed of data transmission should be increased to the range of the example 10Base-T1S ethernet, and the effective data length up to 64 bytes, which has been achieved with CAN FD, should be greater. The robustness of a CAN or CAN FD-based communication network CAN thus advantageously be maintained.

During the detailed description of the analog serial data transmission on the CAN bus line, the transmission level and the reception threshold value of at least one input comparator for the transmitting/receiving device (transceiver) of each subscriber station are then specified for CAN XL. The transmission level and the reception threshold are optimized for the most flexible possible design of the bus line topology and differ in the different operating modes of the transmission/reception device (transceiver).

The disadvantage is that the bit levels of the two logics on the CAN bus line are not always clearly recognized when the receiving transmitting/receiving device is set to a different reception threshold than the transmission of the transmission level on the bus. This may occur in particular when the transmitting/receiving device (transceiver) wakes up from a stationary state and tries to join again in an ongoing communication on the bus. In order to be able to implement such joining of CAN subscriber stations, which have no knowledge of which operating mode is the correct operating mode for the transmitting/receiving device, a third receiving Threshold t_ OoB (Threshold Out-of-Bounds) having a value of, for example, -0.4V is inserted for at least one input comparator.

However, it is problematic that the reception threshold t_ OoB may interfere with synchronization of the subscriber station. The reason for this is that the receive threshold T OoB shifts the bit edge on the connection of the transmitting/receiving device for the RxD signal formed by the signal received from the bus when switching back from the data phase into the arbitration phase.

Disclosure of Invention

The object of the present invention is therefore 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 should be provided, wherein the process of joining a CAN subscriber station into an ongoing communication is improved.

This object is achieved by a transmitting/receiving device for a subscriber station of a serial bus system having the features of claim 1. The transmitting/receiving device has: a first connector for receiving a transmit signal from the communication control device; a transmission module for transmitting a transmission signal onto a bus of a bus system in which at least a first communication phase and a second communication phase are used for exchanging messages between subscriber stations of the bus system; a receiving module for receiving signals from the bus, wherein the receiving module is designed to generate digital received signals from the signals received from the bus; a second connector for transmitting the digital reception signal to a communication control device to receive an operation mode-conversion signal from the communication control device; and an operation mode switching block for evaluating an operation mode switching signal received from the communication control device at a second connector, wherein the operation mode switching block is designed to switch the transmitting module and the receiving module into one of three different operation modes depending on the result of the evaluation, and wherein the operation mode switching block is designed to delay the switching of the operation mode of the second communication phase to the operation mode of the first communication phase in time until a bit boundary of a switching phase between the communication phases.

With the transmitting/receiving device it is possible to prevent "false positives" in CAN idle detection. As a result of this, the subscriber station can be added to the ongoing communication on the bus. Furthermore, the synchronization of the transmitting/receiving means and thus of the upper subscriber stations (CAN nodes) is still achieved or maintained.

Furthermore, with the transmitting/receiving device, an arbitration known from CAN be maintained in one of the communication phases and the transmission rate CAN nevertheless be significantly increased again with respect to CAN or CAN FD. This can be achieved by: two communication phases with different bit rates are used and the start of the second communication phase, in which valid data is transmitted at a higher bit rate than in arbitration, is made reliably identifiable to the transmitting/receiving device. Therefore, the transmitting/receiving device can reliably switch from the first communication phase to the second communication phase or back. As a result of this, a significant increase in the bit rate and thus in the transmission speed from the sender to the receiver can be achieved. At the same time, however, a large error robustness is ensured.

Even if at least one CAN subscriber station and/or at least one CAN FD subscriber station transmitting messages according to the CAN protocol and/or CAN FD protocol is present in the bus system, the method implemented by the transmitting/receiving device CAN also be used.

Further advantageous embodiments of the transmitting/receiving device are specified in the dependent claims.

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

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

If the transmitting/receiving device is the sender of a message in the second communication phase and an edge between different bus states occurs in the transmission signal, the operating mode switching block may be designed to switch the operating mode when switching from the second communication phase into the first communication phase.

The transmitting module may be designed to drive bits of the signal onto the bus in a first communication phase with a first bit time which is at least 10 times greater than a second bit time of the following bits, the transmitting module driving the bits onto the bus in a second communication phase. The operating mode switching signal can have at least one pulse with a pulse duration, which is approximately equal to or shorter than the second bit time, via a second connection for signaling a switching of the operating mode.

The communication control device can be designed to: if a transition from the first communication phase to the second communication phase is to be made, an identifier having a predetermined value is transmitted to the receiving module as an operating mode switching signal on the connection for the digital received signal.

For example, the identifier is a bit having 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 can be considered that in the first communication phase, which of the subscriber stations of the bus system obtains at least temporarily specific, collision-free access to the bus in a subsequent second communication phase.

The above-described transmitting/receiving device and the above-described communication control device can be part of a subscriber station of a bus system, which furthermore comprises a bus and at least two subscriber stations, which are connected to each other via the bus, so that the subscriber stations can communicate with each other in series. At least one of the at least two subscriber stations has the above-described transmitting/receiving device.

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 for subscriber stations of a bus system, wherein at least a first communication phase and a second communication phase are used for exchanging messages between subscriber stations of the bus system, wherein the subscriber stations have a transmitting module, a receiving module, an operating mode conversion block, a first connection and a second connection, and wherein the method has the following steps: receiving signals from a bus of the bus system with the receiving module; generating a digital received signal from the signal received at the bus with the receiving module and outputting the digital received signal at the second junction; evaluating an operating mode-switching signal received at a second junction from the communication control device with the operating mode-switching block; and switching the transmitting module and/or the receiving module into one of three different modes according to the result of the evaluation with the operation mode-switching block, wherein the operation mode-switching block delays the switching of the operation mode of the second communication stage to the operation mode of the first communication stage in time until a bit boundary of a switching stage between the communication stages.

The method provides the same advantages as mentioned before in relation to the transmitting/receiving device and/or the communication control device.

Other possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the examples that are not explicitly mentioned. In this case, the person skilled in the art can also add individual aspects as improvements or additions to the corresponding basic form of the invention.

Drawings

The present invention is described in detail below with reference to the accompanying drawings and according to embodiments. Wherein:

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

fig. 2 shows a diagram for explaining the structure of a message that can be transmitted by a subscriber station of the bus system according to the first embodiment;

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

Fig. 4 shows a circuit diagram of an operation mode-switching block for switching an operation mode of a transmitting/receiving device of the subscriber station of fig. 3;

Fig. 5 to 9 show time profiles of signals according to a first exemplary embodiment in a time phase in which a first operating mode of the transmitting/receiving device which is switched on in an arbitration phase (first communication phase) is switched into one of two operating modes of the transmitting/receiving device, into which the transmitting/receiving device can switch in a data phase as a second communication phase;

Fig. 10 to 15 show time profiles of signals according to the first exemplary embodiment in the time phase in which the operating mode of the transmitting/receiving device for the second communication phase, i.e. the operating mode of the transmitting/receiving device for the data phase, is switched back to the first operating mode, which is the operating mode of the transmitting/receiving device for the arbitration phase;

figures 15 to 17 show time profiles of signals in the subscriber station of figure 3 when the subscriber station attempts to join an ongoing communication on the bus; and

Fig. 18 shows a circuit diagram of an operation mode-switching block for switching an operation mode of the transmitting/receiving device of the subscriber station of fig. 3 according to the second embodiment.

In the drawings, identical or functionally identical elements are provided with the same reference numerals, unless otherwise specified.

Detailed Description

Fig. 1 shows, as an example, a bus system 1 which is essentially designed in particular for a CAN bus system, a CAN FD subsequent bus system and/or modifications thereof, as described below. The bus system 1 can be used in vehicles, in particular in motor vehicles, in aircraft, etc., or in hospitals, etc.

In fig. 1, the bus system 1 has a plurality of subscriber stations 10, 20, 30, which are each connected to a bus 40 having a first bus core 41 and a second bus core 42. The bus lines 41, 42 CAN also be designated as can_h and can_l and serve for the transmission of electrical signals after the coupling-in of a dominant level or the generation of a recessive level for the signal in the transmit state. Messages 45, 46 in the form of signals can be transmitted in series between the individual subscriber stations 10, 20, 30 via the 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 transmission/reception device 12, and a conversion block 15. And the subscriber station 20 has communication control means 21 and transmitting/receiving means 22. The subscriber station 30 has communication control means 31, transmitting/receiving means 32 and a switching block 35. The transmitting/receiving means 12, 22, 32 of the subscriber stations 10, 20, 30, respectively, are directly connected 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 exchanged bit by bit between the respective communication control device 11, 21, 31 and the associated transmitting/receiving device 12, 22, 32 via the TXD and RXD lines, while being encoded in the form of frames. This will be described in more detail below.

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

The communication control device 11, 31 creates and reads a first message 45, for example a modified CAN message 45, which is also referred to below as CAN XL message 45. The modified CAN message 45 or CAN XL message 45 is constructed here on the basis of a CAN FD subsequent format, which is described in more detail with reference to fig. 2. The communication control device 11, 31 can furthermore be produced for: CAN XL message 45 or CAN FD message 46 is provided to or received from the transmitting/receiving device 12, 32 as required. The communication control device 11, 31 thus creates and reads a first message 45 or a second message 46, wherein the first and second messages 45, 46 are distinguished by their data transmission standard, that is to say in this case by CAN XL or CAN FD.

The communication control device 21 can, for example, according to ISO 11898-1:2015, in particular CAN be made as a conventional CAN controller or CAN FD controller compatible with CAN FD. The communication control device 21 creates and reads a second message 46, for example a conventional CAN message or CAN FD message 46. A number of 0 to 64 data bytes CAN be included in the CAN FD message 46, which data bytes are still transmitted for this purpose at a significantly faster data rate than in conventional CAN messages. In the latter case, the communication control device 21 is fabricated as a conventional CAN FD controller.

The transmitting/receiving device 22 CAN be produced as a CAN XL transceiver, apart from the differences which are described in more detail below. Additionally or alternatively, the transmitting/receiving device 12, 32 CAN be produced as a conventional CAN FD transceiver. The transmitting/receiving device 22 CAN be fabricated as a conventional CAN transceiver or CAN FD transceiver.

The formation and subsequent transmission of messages 45 in CAN XL format and the reception of such messages 45 CAN be achieved with the two subscriber stations 10, 30.

Fig. 2 shows a CAN XL frame 450 for message 45 as transmitted by the transmitting/receiving device 12 or the transmitting/receiving device 32. The CAN XL frame 450 is divided for CAN communication on the bus 40 into different communication phases 451 to 455, namely an arbitration phase 451, a first transition phase 452 at the end of the arbitration phase 451, a data phase 453, a second transition phase 454 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 SOF bit and indicates the beginning of the Frame (or Start of Frame). In addition, an identifier with, for example, 11 bits is transmitted in the arbitration phase 451 for identifying the sender of the message 45. In the arbitration, the identifiers are used to agree on a bit-by-bit basis between the subscriber stations 10, 20, 30: which subscriber station 10, 20, 30 wants to transmit the message 45, 46 with the highest priority and thus obtains exclusive access to the bus 40 of the bus system 1 in the transition stage 452 and the following data stage 453 at the next time for transmission.

In the present embodiment, in the first transition stage 452, a transition from the arbitration stage 451 to the data stage 453 is prepared. The protocol format information contained in at least one bit is transmitted here, which is suitable for distinguishing CAN XL frames from CAN frames or CAN FD frames. The transition stage 452 can have a bit AL1, which bit AL1 has a bit duration T_B1 of the bits of the arbitration stage 451 and is sent with the physical layer of the arbitration stage 451. The physical layer corresponds to the bit transport layer or layer 1 of the known OSI model (open systems interconnection model). Furthermore, a Data Length Code (Data Length Code) can be transmitted, for example, 12 bits long, which can then have a value of, for example, 1 to 4096, in particular up to 2048, or other values with a step size of 1, or alternatively can have a value of 0 to 4095 or higher. Alternatively, the data length code can include fewer or more bits, such that the range of values and step sizes can have other values.

In the data phase 453, the CAN XL frame 450 or the payload of the message 45 is transmitted, which CAN also be referred to as the data field of the message 45. The valid data can have data according to a range of values of the data length code, for example having a number of bytes up to 4096 bytes or a larger number of bytes or any other number of data. At the end of the data phase 453, a checksum of the data phase 453 can be contained, for example, in a checksum field, which includes padding bits, which are inserted by the sender of the message 45 as inversion bits after a predetermined number of identical bits, in particular 10 identical bits. In particular, the checksum is a frame checksum f_crc, which is used to protect all bits of the frame 450 up to the checksum field. Thereafter, an FCP field having a predetermined value, e.g., 1100, can follow.

In the present embodiment, a transition from the data stage 453 to the end of frame stage 455 is prepared in the second transition stage 454. Here, protocol format information contained in at least one bit is transmitted, which is suitable for implementing the conversion. The transition stage 454 can have a bit AH1 with the bit duration t_b1 of the bits of the arbitration stage 451, but sent with the physical layer of the data stage 453.

In the end of frame stage 455, at least one acknowledgement bit ACK can be included after two bits AL2, AH2 in the end field in the end of frame stage 455. Thereafter, a sequence of 11 identical bits CAN be followed that indicate the end of the CAN XL frame 450. The receiver CAN be notified with at least one acknowledgement bit ACK whether an error has been found in the received CAN XL frame 450 or message 45.

The physical layer as in CAN and CAN-FD is used at least in the arbitration phase 451 and the end-of-frame phase 455. In addition, the physical layer as in CAN and CAN-FD CAN be used at least partially, i.e. at the beginning, in the first switching phase 452. In addition, the physical layer as in CAN and CAN FD CAN be used at least partially, i.e. at the end, in the second switching phase 454.

An important point during the 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 the subscriber stations 10, 20, 30 to access the bus 40 simultaneously without destroying the messages 45, 46 with higher priority. It is thereby possible to add other bus subscriber stations 10, 20, 30 to the bus system 1 relatively easily, which is highly advantageous.

As a result of the CSMA/CR method, there must be a so-called hidden state on the bus 40 that can be overwritten by other subscriber stations 10, 20, 30 with a dominant state on the bus 40.

Only if the bit time is significantly longer than twice the signal transmission time between two arbitrary subscriber stations 10, 20, 30 of the bus system 1 can arbitration be performed at the beginning of the frame 450 or the message 45, 46 and acknowledgement be performed in the end of frame phase 455 of the frame 450 or the message 45, 46. Thus, the bit rate in the arbitration phase 451, the end of frame phase 455, and at least in part in the conversion 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 stages 451, 452, 454, 455 is chosen to be 500kbit/s, resulting in a bit time of about 2 mus, whereas the bit rate in the data stage 453 is chosen to be 5 to 10Mbit/s or more, resulting in a bit time of about 0.1 mus or less. Thus, the bit time of the signal in the other communication phases 451, 452, 454, 455 is at least 10 times larger than the bit time of the signal in the data phase 453.

The sender of the message 45, for example the subscriber station 10, starts to send bits of the switching phase 452 and the following data phase 453 onto the bus 40 only if the subscriber station 10 has won arbitration as sender and the subscriber station 10 as sender thus has exclusive access to the bus 40 of the bus system 1 for transmission. The sender can either switch to a faster bit rate and/or other physical layer after a portion of the transition stage 452, or can switch to a faster bit rate and/or other physical layer with the first bit of the subsequent data stage 453, i.e. with its beginning.

In general terms, in the bus system with CAN XL, the following distinguishing features CAN be achieved in particular in comparison with CAN or CAN FD:

a) According to the CSMA/CR method, the validated characteristics responsible for the robustness and user friendliness of CAN and CAN FD, in particular the frame structure with identifier and arbitration,

B) Increasing the net data transfer rate to about 10 megabits per second, and

C) The size of the valid data per frame is increased to about 4 kbytes or any other value.

Fig. 3 shows the basic structure of the subscriber station 10 having the communication control means 11, the transmitting/receiving means 12 and the conversion block 15. The subscriber station 30 is constructed in a similar manner to that shown in fig. 3, except that the block 35 is provided separately from the communication control means 31 and the transmitting/receiving means 32. Thus, the subscriber station 30 and the block 35 will not be described separately. The functions of the conversion block 15 described below are identically present in the conversion block 35.

According to fig. 3, the communication control device 11 furthermore has a communication control module 111, a transmission signal output driver 112 and an RxD connector configuration module 113. The communication control device 11 is designed as a microcontroller or has a microcontroller. The communication control 11 processes signals of any application, for example of a control device for a motor, of a safety system for a machine or a vehicle or other application.

However, a system ASIC (asic=application specific integrated circuit) is not shown in fig. 3, which can alternatively be a System Base Chip (SBC) on which various functions necessary for the electronic structural assembly of the subscriber station 10 are incorporated. In particular, the transmission/reception device 12 and a power supply device, not shown, for supplying the transmission/reception device 12 with electrical energy can be installed in the system ASIC. The energy Supply device typically supplies a voltage can_supply of 5V. However, the energy supply device can provide other voltages having other values and/or can be designed as a current source, as desired.

According to fig. 3, the transmitting/receiving device 12 furthermore has a transmitting module 121, a receiving module 122, a driver 123 for transmitting the signal TxD, a receiving signal output driver 124 and a driver 125 for outputting the signal rxd_tc to the switching block 15. The switching block 15 forms a switching signal s_op for switching the operating state of the transmitting module 121 and/or the receiving module 122 from the signal rxd_tc and the signal s_sw, which is the output signal of the receiving module 122. In addition, the switching block 15 forms an operating state switching signal s_opt for switching the reception threshold of the reception module 122 from the signal s_op and the signals TxD, s_sw. The switching signal s_op can include, for example, switching signals for the transmitting module 121 and the receiving module 122 in one bit. Alternatively, the switching signal s_op can be a two-bit wide signal for separately controlling the transmitting module 121 and the receiving module 122 by: such as the first bit being set for switching the transmitting module 121 and the second bit being set for switching the receiving module 122. Of course, any alternative possibility of the design of the switching signal s_op can be envisaged. The transmitting module 121 is also called a transmitter. The receiving module 122 is also called a receiver.

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

Even though the transmitting/receiving device 12 is always referred to below, the receiving module 122 can alternatively be provided in a separate device outside the transmitting module 121. The transmitting module 121 and the receiving module 122 can be constructed as in the conventional transmitting/receiving device 22. The transmitting module 121 can have, in particular, at least one operational amplifier and/or transistor. The receiving module 122 can have, in particular, at least one operational amplifier and/or transistor.

As shown in fig. 3, the transmitting/receiving device 12 is connected to a bus 40, more precisely to a first bus line core 41 for can_h and to a second bus line core 42 for can_l. The first and second bus cores 41, 42 are connected to a transmitting module 121 and a receiving module 122 in the transmitting/receiving device 12. The voltage supply of the energy supply device for supplying the first and second bus lines 41, 42 with electric energy is performed as usual. The connection to ground or can_gnd is also usually made. This applies similarly to the termination of the first and second bus conductors 41, 42 with termination resistors.

The conversion block 15 is designed to identify the start of the respective conversion stage 452, 454 in the message 45 received from the bus 40 and then to convert the characteristics of the transmitting/receiving device 12. The switching block 15 can switch between the following operating modes of the transmitting/receiving device 12:

a) First mode of operation: for the transmit/receive characteristics of the arbitration phase 451,

B) Second mode of operation: as a sender (transmitting node) for the transmission/reception characteristics of the data stage 453, the transmitting/receiving device 12 acts as a sender of the message 45 or the frame 450 and thus also as a receiver of the message 45 or the frame 450,

C) Third mode of operation: as a receiving party (receiving node) for the transmission/reception characteristics of the data stage 453, the transmission/reception device 12 is not a transmitting party, but merely acts as a receiving party of the message 45 or the frame 450.

As described below, the RxD-connector configuration module 113 configures the connector RxD using the signals S1, S2 at its inputs, depending on the necessary communication direction. The signal S1 can be referred to as rxd_out_ena, which does not allow the driving of an additional signal rxd_tc by an RxD connection (first connection-mode of operation) or allows the driving of an additional signal rxd_tc by an RxD connection (second connection-mode of operation). 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 point between two different communication phases in order to signal the transmission/reception device 12 the operating mode to be set, i.e. for switching between the arbitration phase 451 and the data phase 453 in the first switching phase 452 and for switching between the data phase 453 and the end-of-frame phase 455 in the second switching phase 454 on the one hand. Alternatively, the communication control device 11 can drive the connection RxD in a third connection operating mode, which can also be referred to as "talk mode", in which internal communication between the devices 11, 12 is possible, as a function of the value of the signal S2. In other respects, the connection RxD is an Input (Input) to the communication control device 11, as is common in CAN in particular, i.e. 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 bi-directionally by means of the RxD connection configuration module 113 and the signals S1, S2. In other words, the joint RxD is a bi-directional joint.

For this purpose, the communication control device 11 and the output drive 124 are designed in such a way that the communication control device 11 drives the connection RxD more strongly than the output drive 124 when driven for signaling purposes. It is thereby avoided that the value of the RxD line may be uncertain when both the communication control device 11 and the output driver 124 drive the connection RxD and a superposition of two signal sources occurs at the connection RxD. Thus, the communication control device 11 always succeeds when such a superposition of two signal sources occurs at the connection RxD. The value of the RxD line is thus always determined.

The conversion block 15 is thereby able to provide the following possibilities, namely: the setting of one of the three previously mentioned operating modes in the transmitting/receiving device 12, which form the different operating states of the transmitting/receiving device 12, is signaled by the RxD-connector. For this purpose, no additional connections are required on the transmitting/receiving device 12 and thus also on the communication control device 11.

For this purpose, according to fig. 3, the conversion block 15 is provided with three inputs via which the signal rxd_tc, the signal TxD and the signal s_sw are fed into the conversion block 15. The signal rxd_tc is based on a signal sent by the communication control device 11 to the transmitting/receiving device 12 through a connector for RxD signals. The communication control device 11 signals the transmitting/receiving device 12 with a signal rxd_tc on the one hand: the transmitting/receiving device 12 must now make a transition into the operating mode for the data phase 453. At the end of the data phase 453, the communication control device 11 can switch the transmitting/receiving device 12 from the operating mode of the data phase 453 into the operating mode for the arbitration phase 451 with the signal rxd_tc. Furthermore, as mentioned before, any other information can be transmitted by the communication control device 11 to the transmitting/receiving device 12 together with the signal rxd_tc.

According to fig. 3, the transmitting/receiving device 12 directs the signal rxd_tc from the connection RxD via a driver 125 to the connection for the signal rxd_tc of the switching block 15. And the signal s_sw is generated from the signal received from the bus 40. The signal rxd_tc is led to the conversion block 15 between the connection for the RxD signal and the output of the receive signal driver 124. The signal s_sw is led from the output of the receiving module 122 and to the conversion block 15 before receiving the input of the signal driver 124.

According to the particular example shown in fig. 4, the conversion 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 are responsive to rising clock edges of a clock signal, i.e. signal rxd_tc. In addition, a high state or a first binary signal state is applied to the input of the D flip-flop 151 with the signal s_h. Further, an inverse signal s_sw is input as a reset signal to the D flip-flops 151 and 152. The signal s_sw is directed through an inverter 155 before being input into the D flip-flops 151, 152. The D flip-flops 151, 152 are connected to logic gates 156, 157, i.e. to gate 156 and or gate 157. The output of the or-gate 157 is supplied as a clock signal TO a D-flip-flop 158, into which a time-out signal s_to is also supplied as a reset signal, said time-out signal indicating the expiration of a predetermined duration T0. If no edge is found on the bus 40 for a predetermined duration T0, for example 11 bit times, the signal s_to becomes active. The D flip-flop 158 is responsive to rising clock edges. Furthermore, an inverter 159 is connected between the D flip-flop 158 and the input of the and-gate 156. In the particular example of fig. 4, the third D flip-flop 158 is switched from 0 to 1 by two falling edges of the signal rxd_tc when the signal s_sw is high. If the flip-flop 158 is on 1, it is switched from 1 to 0 by the falling edge of the signal rxd_tc when the signal s_sw is high. When the signal s_sw is low, the two D flip-flops 151, 152 are reset and do not respond to the rising edge of the signal rxd_tc.

By means of the block 160, the transmitting/receiving device 12 can first store a switching signal rxd_tc, which contains at least one high pulse driven by the communication control device 11, when transitioning from the data phase 453 to the end-of-frame phase 455. This will be described in more detail below with reference to fig. 5 to 14.

Of course, the switching conditions described above can be defined differently, for example, when the signal s_sw is low, for example, there is a rising edge on the signal rxd_tc. Furthermore, other levels and/or other numbers of edges are possible along with other circuitry in the conversion block 15.

In the particular example of fig. 4, the D flip-flop 158 drives a binary operating state-switching signal s_op. If the switching signal s_op should be two bits wide or if more than two operating states should be displayed, an additional D flip-flop having a different switching condition from the case described above is required.

If the switching block 15 recognizes a switching phase 452, the signal s_op output by the switching block 15 is used to switch the operating state of the transmitting module 121 and/or the receiving module 122 and thus the operating mode of the transmitting/receiving device 12. This is explained in detail with reference to fig. 5 to 9.

In operation of the bus system 1, if the subscriber station 10 acts as a transmitter, the transmitting module 121 converts the transmission signal TxD of the communication control device 11 into the respective signals can_h and can_l for the bus conductors 41, 42 and transmits these signals can_h and can_l onto the bus 40, as is shown in fig. 5 for the transition from the arbitration phase 451 via the transition phase 452 to the data phase 453. In this case, the bit duration t_b1 of the arbitration phase 451 is switched to the shorter bit duration t_b2 of the data phase 453. Even if signals can_h and can_l are mentioned here for the transmitting/receiving device 12, these signals are understood as signals can_xl_h and can_xl_l with respect to message 45, which differ in at least one feature from the conventional signals can_h and can_l in the data phase 453, in particular with respect to the formation of bus states for the different data states of signal TxD and/or with respect to voltage or physical layer and/or bit rate. In the example of fig. 5, in the data phase 453, the signals CAN-xl_h and CAN-xl_l are formed with respect to the bus state for the different data states of signal TxD and differ from the conventional signals can_h and can_l in the phases 451, 452 with respect to the voltage or physical layer and bit rate.

As shown in fig. 6, a differential signal vdiff=can_h-can_l is formed as a result of the signal on the bus 40. In addition to the idle state or the ready state (idle or standby), the transmitting/receiving device 12 with the receiving module 122 always listens to the transmission of data or messages 45, 46 on the bus 40 in normal operation, and this is independent of whether the subscriber station 10 is the transmitting party of the message 45. The receiving module 122 uses the receiving threshold t_a in the arbitration phase 451 and at the beginning of the switching phase 452. At the end of the transition phase 452 and in the data phase 453, the receive module 122 uses only a receive threshold t_d of 0V or between +/-0.1V. The minimum value of the differential voltage for bus state D0 in the data phase 453 is referred to as vdiff_d0_min, which is in the lower range for the receive threshold t_a. The receiving module 122 forms a signal s_sw and forwards this signal as a digital received signal RxD via a received signal output driver 124 to the communication control device 11, as shown in fig. 3. If the transmitting/receiving device 12 is switched into the operating mode for the arbitration phase 451, the device 12 cannot reliably recognize the "0" bit of the data phase 453, since the current switching threshold or the receiving threshold t_a is within the tolerance range of its lower part and therefore may lie below vdiff_d0_min.

Fig. 7 shows a part of a transmission signal TxD, which is transmitted by the subscriber station 10, for example, onto a bus 40. With a delay duration t_tld, which occurs during operation and is also referred to as a transmitter loop delay (TRANSMITTER LOOP DELAY), the subscriber station 10 receives the signal as a transmitter and forms a digital received signal rxd_t from it with the receiving module 122 and the driver 124, as shown in fig. 8. The delay time t_tld depends on temperature, operating voltage and production tolerances and is usually specified in the data page of the transmitting/receiving device 12 and specified within the tolerance limits. In the ideal case there is no delay duration T TLD.

According to fig. 5 to 7, the communication control device 11 successively transmits FDF bits and XLF bits each having a high state (first binary signal state) in the transmission signal TxD before the transition stage 452. Following resXL bits thereafter, the resXL bits are sent with a state low (second binary signal state) and are followed by the AL1 bits sent with a state low (second binary signal state). Then, at the end of the arbitration phase 451, the bits with bit time t_b1 of the arbitration phase 451 are switched from the signal rxd_tc shown in fig. 8 and having pulse duration t_b3 to the bit level and switching threshold of the data phase 453 and are switched with bit time t_b2, as shown in fig. 5 to 9. The pulse duration t_b3 is substantially equal to or less than 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. The AL1 bit is followed by bits DH1, DL1 of the data stage 453 and is followed by valid data. The signal rxd_tc only converts the analog components 121, 122 of the transmitting/receiving device 12. The length of the bit times t_b1, t_b2 is only switched within the digital communication control device 11.

According to fig. 9, the subscriber station 30, which is, for example, merely the receiver of the signal from the Bus 40, receives the signal from the Bus 40 with an additional delay duration t_bld, which is also referred to as Bus line delay (Bus LINE DELAY). From which the subscriber station 30 forms a digital received signal RxD _ R, as shown in fig. 9. Thus, the received signal rxd_r is additionally delayed by a delay duration t_bld compared to the received signal rxd_t.

Thus, according to fig. 8, the transmitting/receiving device 12 of the subscriber station 10 sees a received signal rxd_t which, in the AL1 bit with the second binary signal state (Low), has two high pulses al_2 in a different manner from the previously described profile of the TxD signal of fig. 7. In other words, the communication control device 11 transmits a signal rxd_tc via an RxD connection, in which an identifier in the form of two pulses al_2 having a first binary signal state (high), i.e. opposite signal states, is transmitted in the AL bit. Thereby, the transmitting/receiving device 12 is signaled to switch from its first operating mode into its second operating mode in order to generate the bus signal can_ H, CAN _l from the following bits of the transmission signal TxD. The signal rxd_tc is switched on the edge s_td with a switching block 15. In the second mode of operation, the subscriber station 10 acts as both a sender and a receiver of a message 45 or frame 450.

In contrast, according to fig. 9, the transmitting/receiving device 32 of the subscriber station 30 sees a received signal rxd_r which, unlike the previously described profile of the TxD signal of fig. 7, has a high pulse al_1 in the AL1 bit. In other words, the communication control device 31 transmits a signal rxd_tc via its RxD connection, in which an identifier in the form of a pulse al_1 having a first binary signal state (high), i.e. having the opposite signal state, is transmitted in the AL bit. Thereby signaling the transmitting/receiving device 32 to switch from its first mode of operation to its third mode of operation. The signal rxd_tc causes a transition on the edge s_rd with a transition block 15. In the third mode of operation, the subscriber station 30 acts only as the receiver of the frame 450, that is to say the subscriber station 30 has lost the previous arbitration or has no message 45 to send.

The signaling can thus be performed such that the sequence of two high pulses al_2 indicates a transition from the arbitration phase 451 (first mode of operation) to the data phase 452 as sender (second mode of motion), as shown in fig. 8, and the high pulse al_1 indicates a transition from the arbitration phase 451 (first mode of operation) to the data phase 452 as receiver (third mode of operation), as shown in fig. 9. Thereafter, transmission of data of the data field 453 of the frame 450 can be performed.

The time delay of the block 160 is adjusted to a value of zero when the operation mode of the transmitting/receiving device 12 is changed from the first operation mode (arbitration) to the second or third operation mode. Thus, the receiving module 122 immediately switches the receiving threshold t_a of its arbitration phase 451 to the receiving threshold t_d of the data phase 453. If the transmitting/receiving device 12 is to be switched into the second mode of operation, i.e. if the transmitting/receiving device 12 acts as a transmitter of the frame 450, the transmitting module 121 switches when the transmission signal TxD switches to low (second signal state). Of course, other switching conditions can be envisaged.

As can be seen from fig. 10 to 14, the transmitting/receiving device 12, when transitioning from the data phase 453 to the end-of-frame phase 455, proceeds as follows. As shown in fig. 13, the transmitting/receiving device 12 first stores a switching signal rxd_tc containing a low pulse driven by the communication control device 12 by means of a block 160. The block 160 then waits for an edge on the TxD signal according to fig. 12 and then simultaneously switches its transmitting module 122 and switches its receiving module's receiving threshold from the receiving threshold t_d of the data phase 453 to the receiving threshold t_a for arbitration, i.e. to the switching threshold of its receiving comparator. In addition, the transmitting/receiving device 12 switches on a reception Threshold t_ OoB (Threshold Out-of-Bounds, threshold Out) for its reception comparator in the receiving module.

In contrast, the transmitting/receiving device 32 (which in the example shown is the only receiver of the frame 450) processes as can be seen from fig. 11 and 14 when it transitions out of the data phase 453. 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 then switches the reception threshold of its receiving module from the reception threshold t_d of the data phase 453 to the reception threshold t_a for arbitration, i.e. the switching threshold of its reception comparator. In addition, the transmitting/receiving device 32 switches on a reception Threshold t_ OoB (Threshold Out-of-Bounds) for its reception comparator in the receiving module.

In other words, the communication control device 12, 32 signals the transmitting/receiving device 12, 32 to which it belongs to switch the operation mode of the transmitting/receiving device 12, 32, and the transmitting/receiving device 12, 32 delays the switching until the transmitting/receiving device 12, 32 recognizes a bit boundary. The transmitting/receiving device 12 in the transmitting side recognizes a bit boundary on the edge on the TxD input pin. The transmitting/receiving device 12, 32 in the receiving party (which is not the transmitting party of the frame 450) recognizes the bit boundary on the edge on the CAN bus 40.

This prevents the receive threshold T OoB from interfering with the return switching of the transmitting/receiving device 12 from the data stage 453 to the operating mode of the arbitration stages 455, 451 by shifting the second edge of the AH1 bit on the RxD-connector. Thereby, the synchronization of the subscriber stations 10, 20, 30 of the bus system 1, which would otherwise be moved due to the movement of the second edge of the AH1 bit on the RxD-connector, is not disturbed.

Thus, the reception threshold t_ OoB can be used when joining the subscriber station 10, 20, 30 to an ongoing communication, as shown in fig. 15 to 17. For this purpose, the subscriber station 10, 20, 30 looks for an uninterrupted sequence of 11 recessive bits, i.e. rxd=1 or rxd_r=1 or rxd_t=1. Thereafter, the bus is identified as being in an idle state, i.e., in a quiescent state. This sequence of 11 recessive bits occurs between the dominant ACK bit of one CAN frame 450 and the start bit SOF the next CAN frame 450 or even when no frame 450 at all is transmitted.

In the example of fig. 15 to 17, after the transition of phases 451, 452 into data phase 453, a communication on the bus 40 takes place. The subscriber station which has been switched on first serves as a receiving station only and generates a received signal rxd_r here as signal RxD, as shown in fig. 17. Such as subscriber station 10. Thus, the transmitting/receiving device 12 is first switched into the operating mode for the arbitration phase 451 after switching on for the subscriber station 10. In this case, the reception thresholds t_a, t_ OoB are switched on for the reception module 122, as shown in fig. 16. Since the reception Threshold t_a of the arbitration phase 451 cannot reliably identify a logical "0" bit in the data phase 453, the reception Threshold t_ OoB (Threshold Out-of-Bounds) has become necessary. The reason for this is that the reception threshold t_a is in the range from 0.5V to 0.9V depending on manufacturing tolerances, temperature and operating voltage, as described in detail in ISO 11898-2. If the differential voltage VDIFF is above the range, rxd= "0" = dominant. If the differential voltage VDIFF is below the range, rxd= "1" = recessive. If the differential voltage VDIFF is within the mentioned range, rxD is indeterminate. A logical "0" should be sent as vdiff=1v in the data phase 453. If this voltage is attenuated to vdiff=0.8v at the receiving subscriber station (receiving node) via the bus line, such a voltage VDIFF with the receiving threshold t_a cannot be reliably detected.

According to fig. 17, the subscriber station 10 forms a received signal rxd_r from the signals received from the bus 40 according to fig. 15 and 16 as a function of the reception thresholds t_a and t_ OoB. The state da_r (whose voltage value U for the differential voltage vdiff=can_h-can_l is not above the upper limit of the tolerance range specified for the reception threshold t_a) is, for example, identified as recessive. In contrast, state d_d (whose differential voltage is below the receive threshold t_ OoB) is then identified as dominant. The same applies to the state d_d existing at the time t 1. The value for the threshold t_a is in the range of 0.5V to 0.9V due to the tolerances described above.

Thus, the receive threshold t_ OoB causes the "1" bit in the data stage 453 to be output as a "0" bit and compensates for the "0" bit so unrecognized if its differential voltage VDIFF is attenuated to be within the unsafe range of t_a. Thus, the reception threshold t_ OoB prevents: such subscriber stations erroneously recognize the sequence of data bits as a stationary state of the bus 40 and thus assume that the CAN bus 40 is idle and thus start its own frame, which interferes with the frame that has been transmitted currently.

With the previously described embodiment of the subscriber station 10, no electrical connection is required via additional connections at the communication control device 11 and the transmitting/receiving device 12 connected thereto, in order for the communication control device 11 to be able to transmit the bit level and the switching threshold switching times or other data to the transmitting/receiving device 12. That is, the block 15 advantageously does not require additional connectors that are not available on the standard housing of the transmitting/receiving device 12. Thus, no other larger and costly housing need be replaced by the block 15 to provide additional joints.

Furthermore, the operation mode-conversion block 15 allows the transmitting/receiving device 12 to eliminate the need for a protocol controller function. Such a protocol controller is able to, inter alia, recognize the conversion phase 452 of the message 45 and to start the data phase 453 accordingly. However, since such an additional protocol controller requires a considerable area in the transmitting/receiving device 12 or ASIC, the operating mode conversion block 15 achieves a significant reduction in the resource requirements.

The connection of the operating mode switching block 15 to the usual transmitting/receiving device thus provides a very inexpensive and low-cost solution in order to make it possible for the transmitting/receiving device 12 to see which switching should be performed between its different operating modes, i.e. 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 further switching of the operating modes.

By the described design of the transmitting/receiving device 12, 32, a data rate that is significantly higher than the data rate that CAN be achieved with CAN or CAN-FD CAN be achieved in the data phase 452. Further, as previously described, the data length in the data field of the data stage 453 can be arbitrarily selected. The advantages of CAN with respect to arbitration CAN thus be maintained and, nevertheless, a greater amount of data CAN be transmitted very reliably and thus effectively in a shorter time than hitherto, i.e. no data repetition due to errors is required as explained below.

Another advantage is that no error frames are required in the bus system 1 when transmitting the message 45, but alternatively the error frames can be used. If no error frame is used, the message 45 is no longer corrupted, which eliminates the reason for the necessity of dual transmission of the message. Thereby increasing the net data rate.

If the bus system is not a CAN bus system, the operating mode conversion block 15, 35 CAN be designed or will be designed to respond to further conversion signals. In this case, the operation mode switching block 15, 35 can switch the transmitting module 121 and/or the receiving module 122 into one of at least two different operation modes according to the result of evaluation thereof and switch at least one of the operation modes into the other of the operation modes after expiration of the duration T0 preset in the operation mode switching block 15, 35.

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

Unlike the former embodiment, the conversion block 150 uses the signal s_op as input information instead of the signal rxd_tc. In this way, the advantages of the former embodiment can be obtained.

In other respects, the bus system 1 in the second embodiment is constructed in the same manner as described above in relation to the first embodiment.

All previously described designs of the blocks 15, 35, 150, subscriber stations 10, 20, 30, bus system 1 and the method performed therein can be used singly or in all possible combinations. In particular, all features of the embodiments described above and/or modifications thereof can be combined in any desired manner. As an addition or alternative, the following modifications can be considered in particular.

Although the invention has been described above by way of example with respect to a CAN bus system, the invention CAN be used in each communication network and/or communication method, wherein two different communication phases are used, in which the bus states generated for the different communication phases are different. In particular, the invention can be used when developing other serial communication networks, such as ethernet and/or 10Base-T1S ethernet, fieldbus systems, etc.

The previously described bus system 1 according to the embodiment is described with the aid of a bus system based on the CAN protocol. However, the bus system 1 according to the described embodiment can also be another type of communication network in which data can be transmitted serially with two different bit rates. An advantageous, but not mandatory, premise is that in the bus system 1, at least for a specific time interval, a dedicated, collision-free access of the subscriber stations 10, 20, 30 to the common channel is ensured.

In the bus system 1 of the embodiment, the number and arrangement of the subscriber stations 10, 20, 30 is arbitrary. In particular, the subscriber station 20 can be omitted from the bus system 1. It is possible that one or more of the subscriber stations 10 or 30 are present in the bus system 1. It is conceivable that all subscriber stations in the bus system 1 are identically designed, i.e. that only subscriber station 10 or only subscriber station 30 is present.

Claims (13)

1. A transmitting/receiving device (12; 32) for a subscriber station (10; 30) of a serial bus system (1) has:

a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31);

-a transmission module (121) for transmitting the transmission signal (TxD) onto a bus (40) of the bus system (1), for which bus system (1) at least one first communication phase (451, 452, 454, 455) and one second communication phase (453) are used for exchanging messages (45; 46) between subscriber stations (10, 20, 30) of the bus system (1);

-a receiving module (122) for receiving signals from the bus (40), wherein the receiving module (122) is designed for generating a digital received signal (RxD; rxd_t; rxd_r) from signals received from the bus (40);

A second connection for transmitting the digital received signal (RxD; rxD_T; rxR_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 an operating mode switching signal (RxD_TC) received at the second connection from the communication control device (11; 31),

Wherein the operating mode switching block (15; 35; 150) is designed to switch the transmitting module (121) and/or the receiving module (122) into one of three different operating modes as a function of the evaluation result, and

Wherein the operating mode switching block (15; 35; 150) is designed to delay the switching of the operating mode of the second communication phase (453) to the operating mode of the first communication phase (454, 455, 451, 452) in time until a bit boundary of a switching phase between these communication phases.

2. The transmitting/receiving device (12; 32) according to claim 1, wherein the operating mode-switching block (15; 35) is designed for: if an edge between different bus states occurs 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), the switching of the operating mode takes place during the switching from the second communication phase (453) into the first communication phase (454, 455, 451, 452).

3. The transmitting/receiving device (12; 32) according to claim 1 or 2, wherein the operating mode switching 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 transmitting/receiving device (12; 32) is not the sender of the message (45).

4. The transmitting/receiving device (12; 32) according to claim 1 or 2, wherein the operating mode-switching block (15; 35) is designed for: if the transmitting/receiving device (12; 32) is the transmitter of the message (45) in the second communication phase (453) and an edge between different bus states occurs in the transmission signal (TxD), the switching of the operating mode takes place during the switching from the second communication phase (453) into the first communication phase (454, 455, 451, 452).

5. The transmitting/receiving device (12; 32) according to claim 1 or 2, wherein the transmitting module (121) is designed for: the bits of the signal are driven onto the bus (40) in the first communication phase (451) with a first bit time (t_b1) that is at least 10 times greater than a second bit time (t_b2) of the bits, and the transmitting module (121) drives the bits onto the bus (40) in the second communication phase (453).

6. The transmitting/receiving device (12; 32) according to claim 5, wherein the run mode switching signal (rxd_tc) has at least one pulse with a pulse duration (t_b3) by means of a second tap for signaling a switching of the run mode, the pulse duration (t_b3) being equal to the second bit time (t_b2) or shorter than the second bit time (t_b2).

7. The transmitting/receiving device (12; 32) according to claim 1 or 2, wherein the communication control device (11; 31) is designed for: if a transition from the first communication phase (451, 452) to the second communication phase (453) is to be made, an identifier (AL_1; AL_2) having a predetermined value is transmitted as an operating mode switching signal (RxD_TC) to the receiving module (122) at a connection for the digital received signal (RxD).

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

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

10. The transmitting/receiving device (12; 32) according to claim 1 or 2, 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).

11. The transmitting/receiving device (12; 32) according to claim 1 or 2, wherein in the first communication phase (451, 452, 454, 455) it is agreed which of the subscriber stations (10, 20, 30) of the bus system (1) in the subsequent second communication phase (453) obtains at least temporarily dedicated, collision-free access to the bus (40).

12. A bus system (1) has

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 in series and in which at least one subscriber station (10; 30) has a transmitting/receiving device (12; 32) according to any of claims 1 to 11.

13. Method for communication in a serial bus system (1), wherein the method is performed with a transmitting/receiving device for subscriber stations (10; 30) of the bus system (1), wherein at least one first communication phase (451, 452, 454, 455) and one second communication phase (453) are used for exchanging messages (45; 46) between subscriber stations (10; 20; 30) of the bus system (1), wherein the subscriber stations (10; 30) have a transmitting module (121), a receiving module (122), an operating mode conversion block (15, 35), a first connection and a second connection, and wherein the method has the steps of,

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

Generating a digital received signal (RxD; rxD_ T, rxD _R) from the signals received at the bus (40) with the receiving module (122) and outputting the digital received signal (RxD; rxD_ T, rxD _R) at the second connection,

Evaluating an operating mode switching signal (RxD_TC) received at the second connection from the communication control device (11; 31) by means of the operating mode switching block (15; 35; 150), and

Switching the transmitting module (121) and/or the receiving module (122) into one of three different operating modes by means of the operating mode switching block (15; 35) as a function of the evaluation result,

Wherein the operation mode switching block (15; 35; 150) delays the switching of the operation mode of the second communication phase (453) to the operation mode of the first communication phase (454, 455, 451, 452) in time until a bit boundary of a switching phase between the communication phases.