WO2022106117A1

WO2022106117A1 - Subscriber station for a serial bus system, and method for communication in a serial bus system

Info

Publication number: WO2022106117A1
Application number: PCT/EP2021/077685
Authority: WO
Inventors: Florian Hartwich; Valentin HEINRICH; Franz Bailer; Arthur Mutter
Original assignee: Robert Bosch Gmbh
Priority date: 2020-11-20
Filing date: 2021-10-07
Publication date: 2022-05-27
Also published as: DE102020214649A1

Abstract

Disclosed are a subscriber station (10; 20; 30) for a serial bus system (1) and a method for communication in a serial bus system (1). The subscriber station (10; 29; 30) includes a communication control device (11; 21; 31) for controlling a communication of the subscriber station (10; 20; 30) with at least one other subscriber station (10; 20; 30) in the bus system (1) and analyzing a signal (VDIFF) which is received by a bus (40) of the bus system (1) and in which the bit time (t_bt1) in a first communication phase (451) can differ from a bit time (t_bt2) in a second communication phase (452), the communication control device (11; 21; 31) being configured to sample and analyze the signal (VDIFF), which is received by the bus (40) and is based on a transmit signal (TxD) generated by another subscriber station (10; 20; 30), according to a specified frame (450), the communication control device (11; 21; 31) being configured to switch to an error passive reception mode (B_RX_P) when more than a specified number of errors occurs in the communication on the bus (40), the communication control device (11; 21; 31) being configured to switch from the error passive reception mode (B_RX_P) to a reintegration mode (B_R) when the communication control device (11; 21; 31) samples an error in the signal (VDIFF, RxD) received by the bus (40), and the communication control device (11; 21; 31) being configured to reintegrate the communication on the bus (40) in the reintegration mode (B_R).

Description

description

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

technical field

The present invention relates to a subscriber station for a serial bus system and a method for communication in a serial bus system, which works with a high data rate, as well as great flexibility and great immunity to errors.

State of the art

Bus systems for communication between sensors and control devices, for example in vehicles, should enable the transmission of a large amount of data depending on the number of functions of a technical system or a vehicle. It is often required that the data can be transmitted from the sender to the receiver faster than before and, if necessary, that large data packets can also be transmitted.

In vehicles, a bus system is currently in the introductory phase, in which data is transmitted as messages in the ISO11898-l:2015 standard as a CAN protocol specification with CAN FD. The messages are transmitted between the bus users of the bus system, such as sensors, control units, encoders, etc. To do this, the message is sent on the bus in a frame in which there is a switch between two communication phases. In the first communication phase (arbitration) it is negotiated which of the subscriber stations of the bus system is allowed to send its frame to the bus in the subsequent second communication phase (data phase or sending the user data). CAN FD is used by most manufacturers in the first step with 500kbit/s arbitration bit rate and 2 Mbit/s data bit rate in the vehicle. It is therefore necessary to switch back and forth between a slow operating mode and a fast operating mode during transmission on the bus.

In order to enable even higher data rates in the second communication phase, a successor bus system for CAN FD is currently being developed, which is called CAN XL and is currently being standardized by the CAN in Automation (CiA) organization. In addition to pure data transport via the CAN bus, CAN XL should also support other functions such as functional safety (safety), data security (security) and quality of service (QoS = Quality of Service). These are elementary properties that are required in an autonomously driving vehicle.

CAN XL should support high bit rates in the data phase, for example up to 15 Mbit/s or even 20 Mbit/s. In order to achieve this, transceivers are used whose operating mode can be switched in order to achieve the required high bit rates in the data phase. In contrast, the bit rate in the arbitration phase remains at around 500 kbit/s to enable arbitration.

With CAN FD and CAN XL, error signaling can be activated for errors that occur during communication on the bus. The signaling can be done in particular by sending error codes (error flags) to the bus. Provision is made here for subscriber stations in the bus system to switch to what is known as an error passive state after a certain number of errors have been detected. If a subscriber station is switched to this error-passive state, this subscriber station may not send an active error identifier (error flag) but only a passive error identifier (error flag) on the CAN bus. Because of this, this subscriber station cannot interfere with communication on the CAN bus. After an error flag (error flag), a subscriber station (node) always also sends an error delimiter (error delimiter), which consists exclusively of recessive bits. However, the ISO11898-l:2015 standard for CAN FD and the CiA610-l specification for CAN XL currently provide that such a subscriber station in the error-passive state, if it sees an error, responds to the error with a passive error identifier (Error flag) must be sent to the CAN bus. Such an error can be a local error, for example. A local error is an error that only this subscriber station sees.

To send the passive error identifier (error flag), this subscriber station changes to an operating mode for sending signals in the arbitration phase if the subscriber station is not already switched to this operating mode. However, if communication is taking place on the bus at this time in the data phase of a CAN FD frame or a CAN XL frame, with the bit rate of the data phase being set higher than in the arbitration phase, the subscriber station scans the communication on the bus with a different bit rate than with the bit rate of the current data phase. Therefore, the subscriber stations can randomly sample the passive error identifier (error flag), ie also the error delimiter (error delimiter), and therefore recognize it as validly sent on the bus. This can mean that communication on the bus is unintentionally disrupted.

Disclosure of Invention

It is therefore the object of the present invention to provide a subscriber station for a serial bus system and a method for communication in a serial bus system which solve the aforementioned problems. In particular, a subscriber station for a serial bus system and a method for communication in a serial bus system are to be provided, in which a high error robustness of the communication and error signaling can be implemented even with different bit rates in the arbitration and data phase.

The object is achieved by a subscriber station for a serial bus system having the features of claim 1. The subscriber station has a communication control device for controlling communication between the subscriber station and at least one other subscriber station bus system, and for evaluating a signal received from a bus of the bus system, in which the bit time in a first communication phase can differ from a bit time in a second communication phase, the communication control device being designed to process the signal received from the bus, which is on one of based on a transmission signal generated by another subscriber station, sampled and evaluated according to a predetermined frame, the communication control device being designed to switch to an error-passive reception mode if more than a predetermined number of errors occur during communication on the bus, the communication control device is configured to switch from the error passive reception mode to a re-integration mode when the communication controller detects an error in the signal received from the bus, and wherein the communication controller is configured to be in the Re-integration mode to re-integrate into the communication on the bus.

The subscriber station described prevents the subscriber station, which is switched from the error-passive state to the operating mode of the arbitration phase, from scanning a frame that another subscriber station (sending node) sends in the data phase with a higher bit rate, with the lower bit rate of the arbitration phase. It is therefore no longer dependent on the frame currently being sent over the bus, which a subscriber station which is currently only the recipient of a message transmitted over the bus (receiving node) scans from the received message.

The subscriber station described ensures that it does not inadvertently disrupt communication on the bus in the error-passive state.

The subscriber station described thus contributes to CAN communication, in which there is a switchover between two different bit rates, becoming more robust and reliable. Reliable and robust communication with CAN FD or CAN XL is thus possible with the subscriber station even when error signaling is activated.

It is also advantageous that the configuration of the subscriber station described for solving the above-mentioned task can be implemented in a simple and therefore cost-effective manner.

It is thus possible with the subscriber station in the bus system to maintain an arbitration known from CAN in a first communication phase and nevertheless to increase the transmission rate again considerably compared to CAN or CAN FD.

The method carried out by the subscriber station can also be used if there is also at least one CAN subscriber station and/or at least one CAN FD subscriber station in the bus system which sends messages according to the CAN protocol and/or CAN FD protocol.

Advantageous further refinements of the subscriber station are specified in the dependent claims.

The communication controller may be configured to synchronize in the re-integration mode on an edge in a predetermined field of the predetermined frame.

The communication controller may be configured to restart a search for an idle or ready condition in the re-integration mode each time the communication controller has detected a falling edge in the error in the signal received from the bus.

The communication control device can be designed in such a way that the communication control device in the error passive reception mode may not send any active error identification to the bus if the Communication control device has detected an error in communication on the bus.

According to an embodiment, the communication control device has an evaluation block for evaluating the signal received from the bus and a mode switching block for switching the operating mode of the communication control device based on the evaluation performed by the evaluation block.

The subscriber station described above can also have a transceiver for sending a transmission signal onto the bus of the bus system and/or for receiving a signal from the bus of the bus system.

The communication control device can be configured to generate the transmission signal, with the communication control device being configured to use pulse width modulation in the transmission signal to signal the transmission/reception device that the transmission/reception device is changing its operating mode to an operating mode for transmission in the first communication phase or to a has to switch mode for sending in a second communication phase.

According to one embodiment, the subscriber station described above is a CAN XL subscriber station.

The predetermined framework may be constructed in a way that is compatible with CAN FD.

According to one embodiment, the subscriber station described above is a CAN FD subscriber station.

Additionally or alternatively, the communication control device can be configured to negotiate with the other subscriber stations in the first communication phase which of the subscriber stations of the bus system is given at least temporarily exclusive, collision-free access to the bus in the subsequent second communication phase. The subscriber station described above can be part of a bus system which also includes 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 in series. In this case, at least one of the at least two subscriber stations is a previously described subscriber station.

The aforementioned object is also achieved by a method for communication in a serial bus system according to claim 12. The method is carried out with a subscriber station of the bus system, which has a communication control device, the method having the steps of controlling, with a communication control device, communication between the subscriber station and at least one other subscriber station of the bus system, and evaluating a signal received from a bus of the bus system , in which the bit time in a first communication phase can differ from a bit time in a second communication phase, the communication control device sampling and evaluating the signal received from the bus, which is based on a transmission signal generated by another subscriber station, according to a predetermined frame, wherein the communication controller switches to an error passive reception mode if more than a predetermined number of errors occur in the communication on the bus, the communication controller being informed of the error pas siv- receiving mode switches to a re-integration mode when the communication controller detects an error in the signal received from the bus, and wherein in the re-integration mode the communication controller reintegrates into communication on the bus.

The method offers the same advantages as previously mentioned in relation to the subscriber station.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with regard to the exemplary embodiments that are not explicitly mentioned. Included 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 attached drawing and using 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 which can be sent by a transceiver for a subscriber station 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;

4 shows a time course of bus signals CAN_XL_H and CAN_XL_L in the subscriber station according to the first exemplary embodiment;

5 shows a time curve of a differential voltage VDIFF of the bus signals CAN_XL_H and CAN_XL_L in the subscriber station according to the first exemplary embodiment; and

6 shows a diagram of operating modes between which the subscriber station of the bus system can be switched according to the first exemplary embodiment.

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

Description of the exemplary embodiments

Fig. 1 shows an example of a bus system 1, which is particularly fundamental to a CAN bus system, a CAN FD bus system, a CAN XL bus system, and / or Modifications thereof is configured 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.

In FIG. 1, the bus system 1 has a large number of subscriber stations 10, 20, 30, which are each connected to a bus 40 with a first bus wire 41 and a second bus wire 42. The bus cores 41, 42 can also be called CAN_H and CAN_L or CAN_XL_H and CAN_XL_L and are used for electrical signal transmission after the dominant level has been coupled in or generation of recessive levels or other levels for a signal in the transmission state. Messages 45, 46 in the form of signals can be transmitted serially between the individual subscriber stations 10, 20, 30 via the bus 40. If an error occurs during communication on the bus 40, as represented by the jagged black block arrow in FIG. 1, an error frame 47 (error frame) with an error identifier (error flag) and an error delimiter (error delimiter) can optionally be sent. This is described in more detail with reference to FIG. The subscriber stations 10, 20, 30 of FIG. 1 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 transceiver 12 and an operating mode determination module 15. The subscriber station 20 has a communication control device 21, a transceiver 22 and optionally an operating mode determination module 25. The subscriber station 30 has a communication control device 31, a transceiver 32 and an operating mode determination module 35. The transceivers 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.

The communication control devices 11, 21, 31 are each used to control communication between the respective subscriber station 10, 20, 30 via the bus 40 and 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 modified CAN messages 45, for example. In this case, the modified CAN messages 45 are constructed on the basis of a CAN XL format, which is described in more detail with reference to FIG. 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 transceiver 32 or to receive it from the latter, as required. Here, too, the respective operating mode determination modules 15, 35 are used. The communication control devices 11, 31 thus create and read a first message 45 or a second message 46, with the first and second message 45, 46 differing in their data transmission standard, namely CAN XL or CAN FD in this case.

The communication control device 21 can be designed like a conventional CAN controller according to ISO 11898-1:2015, i.e. like a CAN FD tolerant Classical CAN controller or a CAN FD controller. In addition, the operating mode determination module 25 is optionally available, which has the same function as the operating mode determination modules 15, 35. The communication control device 21 creates and reads second messages 46, for example CAN FD messages 46. In the CAN FD messages 46, a A number of 0 to 64 data bytes can be included, which are also transmitted at a significantly faster data rate than with a classic CAN message. In particular, the communication control device 21 is designed like a conventional CAN FD controller.

The transceiver 22 can be designed like a conventional CAN transceiver according to ISO 11898-1:2015 or CAN FD transceiver. The transmitting/receiving devices 12, 32 can be designed to provide or receive messages 45 according to the CAN XL format or messages 46 according to the current CAN FD format for the associated communication control device 11, 31 as required. With the two subscriber stations 10, 30, a formation and then transmission of messages 45 with the CAN XL format and the receipt of such messages 45 can be implemented.

2 shows a CAN XL frame 450 for the message 45, as is provided by the communication control device 11 for the transceiver 12 for transmission onto the bus 40. Here, the communication control device 11 creates the frame 450 in the present exemplary embodiment as being compatible with CAN FD, as also illustrated in FIG. 2 . The same applies analogously to the communication control device 31 and the transceiver 32 of the subscriber station 30.

According to Fig. 2, the CAN XL frame 450 for the CAN communication on the bus 40 is divided into different communication phases 451, 452, namely an arbitration phase 451 and a data phase 452. The frame 450 has an arbitration field 453 after a start bit (SOF). , a control field 454 with an ADS field for switching between the communication phases 451, 452, a data field 455, a checksum field 456 and a frame termination field 457 in which a DAS field for switching between the communication phases 452, 451 is present. This is followed by an end-of-frame field EOF.

In the arbitration phase 451, an identifier (ID) with, for example, bits ID28 to ID18 in the arbitration field 453 is used to negotiate bit by bit between the subscriber stations 10, 20, 30 as to which subscriber station 10, 20, 30 is sending the message 45, 46 with the highest priority wants and therefore gets exclusive access to the bus 40 of the bus system 1 for the next time for sending in the subsequent data phase 452. In the arbitration phase 451, a physical layer is used as in CAN and CAN-FD. The physical layer corresponds to the physical layer or layer 1 of the well-known OSI model (Open Systems Interconnection model).

An important point during phase 451 is that the known CSMA/CR method is used, which allows subscriber stations 10, 20, 30 to access the bus 40 simultaneously without the higher-priority message 45, 46 being destroyed. This allows the bus system 1 further bus subscriber stations 10, 20, 30 can be added 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 can be overwritten by other subscriber stations 10, 20, 30 with dominant states on the bus 40. In the recessive state, the individual subscriber stations 10, 20, 30 have high-impedance conditions, which, in combination with the parasites of the bus wiring, results in longer time constants. This leads to a limitation of the maximum bit rate of today's CAN FD physical layer to around 2 megabits per second in real vehicle use.

In the data phase 452, in addition to part of the control field 454, the user data of the CAN-XL frame or the message 45 from the data field 455 and the checksum field 456 are sent. This is followed by the DAS field, which is used to switch from the data phase 452 back to the data phase 451.

A sender of the message 45 does not start sending bits of the data phase 452 to the bus 40 until the subscriber station 10 as the sender has won the arbitration and the subscriber station 10 as the sender thus has exclusive access to the bus 40 of the bus system 1 for sending .

In general, the following deviating properties can be realized in the bus system with CAN XL compared to CAN or CAN FD: 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 frame structure with identifier and arbitration according to the CSMA/CR method, b) increasing the net data transmission rate, in particular to around 10 megabits per second, c) increasing the size of the user data per frame, in particular to around 2kbyte or any other value.

As shown in FIG. 2, in the arbitration phase 451 as the first communication phase, the subscriber station 10 partly uses, in particular up to the FDF bit (inclusive), a format known from CAN/CAN-FD according to 15011898-1:2015. In contrast, the subscriber station 10 uses a CAN XL format from the FDF bit in the first communication phase and in the second communication phase, the data phase 452, which is described below.

In the present exemplary embodiment, CAN XL and CAN FD are compatible. In this case, the res bit known from CAN FD, which is referred to below as the XLF bit, is used to switch from the CAN FD format to the CAN XL format. Therefore, the frame formats of CAN FD and CAN XL are the same up to the res bit or XLF bit. A receiver only recognizes the format in which the frame 450 is sent from the res bit. A CAN XL subscriber station, in this case subscriber stations 10, 30, also supports CAN FD.

As an alternative to the frame 450 shown in FIG. 2, in which an identifier (ID28 to ID18) with 11 bits is used, a CAN XL extended frame format is optionally possible, in which an identifier (identifier) with 29 bits is used. Up to the FDF bit, this extended frame format is identical to the well-known CAN FD extended frame format from ISO11898-l:2015.

According to FIG. 2, the frame 450 from the SOF bit up to and including the FDF bit is identical to the CAN FD Base Frame Format according to ISO11898-1:2015. Therefore, the known structure is not explained further here. Bits shown with a heavy dash on their bottom line in Figure 2 are sent in frame 450 as dominant or '0'. Bits shown with a heavy dash on their top line in Figure 2 are sent in frame 450 as recessive or '1'. In the CAN XL data phase 452, symmetrical '1' and '0' levels are used instead of recessive and dominant levels.

In general, when the frame 450 is generated, two different stuffing rules are applied. The dynamic bit stuffing rule of CAN FD applies up to before the FDF bit in the arbitration field 453, so that an inverse stuff bit is to be inserted after 5 identical bits in a row. In the data phase 452 up to before the FCP field, a fixed stuffing rule applies, so after a fixed number of bits insert a fixed stuff bit. Alternatively, instead of just one stuff bit, a number of 2 or more bits can be inserted as fixed stuff bits.

In the frame 450, right after the FDF bit is the XLF bit, which corresponds in position to the "res bit" in the CAN FD Base Frame format, as mentioned earlier. If the XLF bit is sent as 1, i.e. recessive, it identifies frame 450 as a CAN XL frame. For a CAN FD frame, the communication control device 11 sets the XLF bit as 0, ie dominant.

Following the XLF bit in frame 450 is a resXL bit which is a dominant bit for future use. For frame 450, the resXL must be sent as 0, i.e. dominant. However, if the subscriber station 10 receives a resXL bit as 1, i.e. recessive, the receiving subscriber station 10 goes, for example, into a protocol exception state (protocol exception state), as is the case with a CAN FD message 46 for a res=1. Alternatively, the resXL bit could be defined the other way around, meaning that it must be sent as 1, i.e. recessive. In this case, the receiving subscriber station goes into the protocol exception state if the resXL bit is dominant.

The resXL bit is followed in frame 450 by an ADS (arbitration data switch) sequence, in which a predetermined bit sequence is encoded. This bit sequence allows a simple and safe switching from the bit rate of the arbitration phase 451 (arbitration bit rate) to the bit rate of the data phase 452 (data bit rate). The first bit of the ADS field is the ADH bit. Optionally, the operating mode of the transceiver 12, 32 is switched from the operating mode B_451 (SLOW) of the arbitration phase 451 to one of two operating modes B_452_TX, B_452_RX of the data phase 452 within the ADH bit. The two operating modes of the data phase 452 are a B_452_TX (FAST_TX) operating mode for a transmitting node that is allowed to send its signal on the bus 40 in the data phase 452, and a B_452_RX (FAST_RX) operating mode for a receiving node that only receives the signal from the bus 40 is.

The following fields up to the beginning of data field 455 are not described in detail here. The data field 455 can have up to 2048 bytes. The data field 455 in the frame 450 is followed by the checksum field 456 with a frame checksum FCRC and an FCP field. FCP = Frame Check Pattern applies here. The FCP field consists of 4 bits with the bit sequence 1100 in particular. A receiving node uses the FCP field to check whether the receiving node is bit-synchronous with the transmission data stream. In addition, a receiving node synchronizes to the falling edge in the FCP field.

The frame termination field 457 follows the FCP field. The frame termination field 457 consists of two fields, namely the DAS field and the acknowledgment field or ACK field with at least one bit ACK and the bit ACK-Dlm.

The DAS field contains the sequence DAS (Data Arbitration Switch) in which a predetermined bit sequence is encoded. The bit sequence DAH, AHI, ALI allows a simple and safe switching from the data bit rate of the data phase 452 to the arbitration bit rate of the arbitration phase 451. In addition, during the DAS field, the operating mode of the transceiver 12, 32, optionally from an operating mode B_452_TX or B_452_RX (FAST) switched to operating mode B_451 (SLOW). The physical layer, ie the operating mode of the transceiver 12, 32, is switched over from FAST_TX or FAST_RX to SLOW within the DAH bit. Bit AH1 is followed by bit ALI (logical 0) and bit AH2 (logical 1). The two bits DAH and AH1 ensure that there is enough time for the operating mode switchover of the transceiver 11 and that all subscriber stations 10, 30 have a recessive level of significantly more than one arbitration bit time before the edge at the start of the AL2 bit ( logical 0) see. This ensures reliable synchronization of the subscriber stations in the bus system, which are currently being reintegrated into the communication on the bus 40 .

In the frame termination field 457, the sequence of the DAS field is followed by the acknowledgment field (ACK). Bits for acknowledging or not acknowledging correct receipt of frame 450 are provided in the acknowledgment field. After the end of frame field 457 in the frame 450 follows an end field (EOF = End of Frame). The end of field (EOF) bit sequence is used to identify the end of frame 450 . The end field (EOF) causes a number of 8 recessive bits to be sent at the end of the frame 450 . This is a bit sequence that cannot occur within frame 450. As a result, the end of the frame 450 can be reliably recognized by the subscriber stations 10, 20, 30.

The end field (EOF) has a length that differs depending on whether a dominant bit or a recessive bit was seen in the ACK bit. If the sending subscriber station has received the ACK bit as dominant, then the end field (EOF) has a number of 7 recessive bits. Otherwise the end field (EOF) is only 5 recessive bits long.

The end field (EOF) is followed in frame 450 by an inter frame space (IFS) which is not shown in FIG. This interframe spacing (IFS) is designed as with CAN FD according to ISO11898-1:2015. The Inter Frame Space (IFS) has at least 3 bits.

3 shows the basic structure of the subscriber station 10 with the communication control device 11, the transceiver 12 and the operating mode determination module 15, which is part of the communication control device 11. Subscriber station 30 is constructed in a manner similar to that shown in FIG. 3, but operating mode determination module 35 according to FIG. Therefore, the subscriber station 30 will not be described separately.

According to Fig. 3, the subscriber station 10 has, in addition to the communication control device 11 and the transceiver 12, a microcontroller 13, to which the communication control device 11 is assigned, and a system ASIC 16 (ASIC = application-specific integrated circuit), which alternatively has a system basis -Chip (SBC) can be, on which several for an electronic assembly of the subscriber station 10 necessary functions are summarized. In the system ASIC 16, in addition to the transceiver 12, an energy supply device 17 is installed, which supplies the transceiver 12 with electrical energy. The energy supply device 17 usually supplies a voltage CAN_Supply of 5 V. However, depending on the requirement, the energy supply device 17 can supply a different voltage with a different value. Additionally or alternatively, the energy supply device 17 can be designed as a current source.

The operating mode determination module 15 has an evaluation block 151, an operating mode switching block 152 and an error counting block 153. The blocks 151, 152, 153 are described in more detail below.

The transmitter/receiver device 12 also has a transmitter module 121 and a receiver module 122. Although the transmitter/receiver device 12 is always referred to below, it is alternatively possible to provide the receiver module 122 in a separate device external to the transmitter module 121. The transmission module 121 and the reception module 122 can be constructed as in a conventional transmission/reception device 22 . In particular, the transmission module 121 can 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.

The transceiver 12 is connected to the bus 40, more precisely its first bus core 41 for CAN_H or CAN_XL_H and its second bus core 42 for CAN_L or CAN_XL_L. The power supply for the energy supply device 17 for supplying the first and second bus wires 41, 42 with electrical energy, in particular with the voltage CAN supply, takes place via at least one connection 43. The connection to ground or CAN_GND is implemented via a connection 44 . The first and second bus wires 41, 42 are terminated with a terminating resistor 49. The first and second bus wires 41, 42 are connected in the transceiver 12 not only to the transmitter module 121, which is also referred to as a transmitter, but also to the receiver module 122, which is also referred to as a receiver, even if the connection in 3 is not shown for the sake of simplicity.

During operation of the bus system 1, the transmission module 121 converts a transmission signal TXD or TxD from the communication control device 11 into corresponding signals CAN_XL_H and CAN_XL_L for the bus cores 41, 42 and transmits these signals CAN_XL_H and CAN_XL_L to the connections for CAN_H and CAN_L on the bus 40.

The reception module 122 forms a reception signal RXD or RxD from the signals CAN_XL_H and CAN_XL_L received from the bus 40 according to FIG. 4 and forwards this to the communication control device 11, as shown in FIG.

According to the example in FIG. 4, the signals CAN_XL_H and CAN_XL_L have the dominant and recessive bus levels 401, 402, at least in the arbitration phase 451, as is known from CAN. A differential signal VDIFF=CAN_XL_H−CAN_XL_L forms on the bus 40, which is shown for the arbitration phase 451 in FIG. The individual bits of the signal VDIFF with the bit time t_btl can be recognized in the arbitration phase 451 with a receiving threshold T_a of 0.7 V, for example. In the data phase 452, the bits of the signals CAN_XL_H and CAN_XL_L can be sent faster, i.e. with a shorter bit time t_bt2, than in the arbitration phase 451. The signals CAN_XL_H and CAN_XL_L in the data phase 452 therefore differ from the conventional signals at least in their faster bit rate CAN_H and CAN_L.

The sequence of states 401, 402 for the signals CAN_XL_H, CAN_XL_L in FIG. 4 and the resulting curve of the voltage VDIFF in FIG selectable as required. In other words, when it is switched to a first operating mode B_451 (SLOW), transmit module 121 generates, according to Fig. 4, a first data state as bus state 402 with different bus levels for two bus wires 41, 42 of the bus line and a second data state as bus state 401 the same bus level for the two bus cores 41, 42 of the bus line of the bus 40.

In addition, the transmission module 121 sends the bits at a higher bit rate to the bus 40 for the time profiles of the signals CAN_XL_H, CAN_XL_L in a second operating mode B_452_TX (FAST_TX), which includes the data phase 452. The CAN_XL_H and CAN_XL_L signals can be in the data phase 452 can also be generated with a different physical layer than with CAN FD. This allows the bit rate in the data phase 452 to be increased even more than with CAN FD. A subscriber station (receiving node) which is not a transmitter of frame 450 in data phase 452, ie is not a transmitting node, sets a third operating mode B_452_RX (FAST_RX) in its transmitting/receiving device.

To signal the changeover from the B_451 operating mode to the B_452_TX (FAST_TX) operating mode or the B_452_RX (FAST_RX) operating mode, the communication control device 11 carries out a pulse width modulation (PWM) of the transmission signal TxD. For this purpose, the communication control device 11 uses one or more PWM symbols per logical bit of the CAN XL frame 450. Basically, a PWM symbol consists of two phases, namely a 0-phase and a 1-phase. In addition, a PWM symbol is delimited by two equal edges, for example by two rising edges.

If the operating mode of the transceivers 12, 32 is not to be switched over, there is also no pulse width modulation (PWM) for coding the signaling for the transmission signal TxD. Thus, the signal that the transceiver 12, 32 drives onto the bus 40 as a differential voltage VDIFF when the transceiver 12, 32 acts as a transmit node is identical to the transmit signal TxD.

The mode of operation of the operating mode determination module 15 is described in more detail below with reference to FIG. 6 . In a diagram, FIG. 6 illustrates a change in the communication control device 11 between different operating modes. It is assumed here that the communication control device 11 currently does not want to send any frames 450 to the bus 40 . Therefore only the case is shown in which the communication control device 11 serves as a receiver of frames 450, more precisely is a receiving node.

In the B_LB (idle) operating mode, the communication control device 11 is switched to the idle or standby state. This means that the communication control device is waiting to receive a message 45, 46. In this state, there is no communication on the bus 40. In other words, no signal is received at the RXD connection of the communication control device 11 or the value is logical 1 since the recessive level corresponds to a logical 1.

If the communication control device 11 is switched to the B_LB (idle) operating mode and receives a level other than logic 1 for the RxD signal from the transceiver 12, in particular the first bit (SOF) of a frame 450, the operating mode switching block 152 switches the Communication control device 11 in a reception mode B_RX.

In the receive mode B_RX, the communication controller 11 receives signals from the bus 40 as an RxD signal, as previously described. In addition, the count value of the error counting block 153 has not yet exceeded a predetermined count value when counting up. Therefore, the communication control device 11 is in a state that can also be called “Error Active” state. In this state, the subscriber station 10 may send an active error code 47_A to the bus 40 in the event of an error in order to communicate the error to the other subscriber stations 10, 20, 30.

An error, as shown by the black block arrow in FIG. 6, can occur at any time during communication in the bus system 1. For example, an error may occur because, for example, a electromagnetic radiation has changed the level on the bus cores CAN_XL_H and CAN_XL_L and the subscriber station 10 as receiving node has sampled a fixed stuff bit with logic 0 during ongoing communication on the bus 40, although the fixed stuff bit was sent as logic 1. Of course, other errors are possible, in particular a single bit is sampled with a different value than expected. Depending on the corrupted bit, the error may only be discovered by one of the two checksums or CRC checks (PCRC, FCRC).

In the reception mode B_RX, the communication control device 11 samples the RxD signal and evaluates it with the aid of the evaluation block 151 in relation to the frame 450 . If the communication control device 11, in particular its evaluation block 151, detects an error when scanning the RxD signal, the operating mode switching block 152 switches the communication control device 11 to an operating mode B_47_A.

The communication control device 11 can be set up to receive bits of the first communication phase 451 or to receive bits of the second communication phase 452 exclusively in the reception mode B_RX, depending on the point at which the frame 450 is currently being received. With the change to another operating mode, such as operating mode B_47_A, the communication control device changes to an operation for receiving bits in the first communication phase 451.

In the operating mode B_47_A, the communication control device 11 sends the active error identifier 47_A at its TXD connection to the bus 40. The active error identifier 47_A has six dominant bits in a row. The active error identifier 47_A is the first part of an error frame 47 as shown in FIG. In addition, the counter value of the error counter block 153 is changed, in particular incremented, by a predetermined value. The received active error identifier 47_A can be lengthened by superimposing the active error identifiers 47_A, which are sent by different subscriber stations as a reaction to the first active error identifier 47_A. Thereafter, the operating mode switching block 152 switches the communication control device 11 to an operating mode B_47_DL. In the operating mode B_47_DL, the communication control device 11 sends an error delimiter 47_DL, which is also referred to as an error delimiter, at its TXD connection to the bus 40. The error delimiter 47_DL has eight recessive bits in a row. The error delimiter 47_DL is the second and last part of the error frame 47 as shown in FIG. Alternatively, the count value of the error counting block 153 can now be changed by a predetermined value. Thereafter, the operating mode switching block 152 switches the communication control device 11 to an operating mode B_IM.

The error frame 47 from active error identifier 47_A and error limiter 47_DL destroys the frame 450 previously sent by another subscriber station of the bus system 1. As a result, the communication on the bus 40 is intentionally disrupted in order to signal the error.

In the operating mode B_47_IM, all subscriber stations 10, 20, 30 of the bus system 1 wait for a predetermined number of recessive bits, which must be present between two frames 450 during communication on the bus 40. As previously mentioned, such an Inter Frame Space (IFS) has at least 3 bits. The communication control device 11 therefore expects the predetermined number of recessive bits that are present in the communication on the bus 40 between two frames 450 in the B_47_IM operating mode. Thereafter, the mode switching block 152 switches the communication control device 11 back to the B_LB mode.

As soon as the communication control device 11 in the B_LB (idle) operating mode receives a level other than logic 1 for the RxD signal from the transceiver 12, in particular the first bit (SOF) of a frame 450, the operating mode switching block 152 switches the communication control device 11 back to the reception mode B_RX, as previously described.

However, if the value of the error counting block 153 exceeds a predetermined value, the mode switching block 152 switches the Communication control device 11 in an error passive reception mode B_RX_P.

Also in the error passive reception mode B_RX_P, the communication control device 11 receives signals from the bus 40 as an RxD signal, as previously described. The communication control device 11 scans the RxD signal and evaluates it with the aid of the evaluation block 151 in relation to the frame 450 . However, if the communication control device 11, in particular its evaluation block 151, detects an error when scanning the RxD signal, the operating mode switching block 152 switches the communication control device 11 to a B_R operating mode. Optionally, upon detection of the error, the evaluation block 151 can instruct the error counter block 153 to change, in particular to increment, the counter value by a predetermined value.

In the re-integration operating mode B_R, the subscriber station 10, in particular the evaluation block 151, searches for an idle or standby condition (idle). In the international standard according to ISO11898-1:2015, the idle or ready condition corresponds to a number of 11 recessive bits in a row. If the evaluation block 151 of the operating mode determination module 15 evaluates that the idle or standby condition (idle) was received, the operating mode switching block 152 switches the communication control device 11 to the B_LB operating mode. The evaluation block 151 restarts the search for the idle or ready condition each time it has detected a falling edge in the RxD signal. It can thus be ruled out that the evaluation block 151 accidentally detects the idle condition prematurely while the transmitting subscriber station is still transmitting in the second communication phase 452 .

As described above with reference to FIG. 2 , the communication control device 11 synchronizes itself in the re-integration operating mode B_R at an edge provided for this purpose in the frame 450 or the signal RxD received from the bus 40 . Thus, the communication control device 11 can be synchronized with the other subscriber stations that may have the frame 450 received correctly, switch to the B_LB operating mode and take part in the communication in the bus system 1 again.

The subscriber station 10 therefore does not send a passive error identifier 47_P in the error-passive reception mode B_RX_P if the subscriber station 10, in particular its evaluation block 151, as the receiving node, detects an error when receiving a frame 450. A passive error identifier 47_P has six recessive bits in a row.

The error counting block 153 decrements its count by a specific value when a frame 450 is correctly received. The count can thus fall below the specific threshold and the subscriber station 10 can thus again respond to an error with an active error identifier 47_A.

As a result, with CAN XL, the error signaling for errors that occur during communication on the bus 40 can still be activated with a high level of error robustness, even given a different bit rate in the communication phases 451, 452.

The operating mode determination module 25 can also be implemented in the same way as described above for the modules 15, 35. Thus, even in the case of CAN FD with a different bit rate in the communication phases 451, 452, the error signaling for errors that occur during communication on the bus 40 can still be activated with great error robustness.

The subscriber stations 10, 30 prevent the currently transmitted CAN FD or CAN XL frame from being disturbed by a receiving node that is switched to the error-passive operating mode B_RX_P.

Subscriber stations 20, in particular their module 25, can have the same functions as described above for module 15.

In the error-passive reception mode B_RX_P, a receiving subscriber station therefore does not respond to a reception error with a passive error identifier 47_P and an error limiter 47_DL. This will make the In the event of an error, this effectively prevents an overlapping of two frames 450 from occurring on the bus 40, which destroys both frames 450. The same applies to CAN FD frames.

Such an error case could occur on the one hand if the receiving node, in particular its evaluation block 151, considers its passive error identifier (6 recessive bits) and an error delimiter (error delimiter, 8 recessive bits) to be complete, i.e. has seen it as recessive, and the 3 bits of the correctly saw the intermission field as recessive. Then the receiving node randomly samples 6 + 8 + 3 = 17 recessive bits in sequence and therefore starts sending a frame, although the sending node is still sending its frame.

On the other hand, such an error case could occur if the receiving node randomly samples 6 + 7 = 13 recessive bits in a row, since the receiving node uses its own passive error identifier (6 recessive bits) and the error delimiter (error delimiter, the first 7 recessive bits) as quasi complete. If the receiving node now samples a dominant bit in the next 3 bits, namely the 8th bit of the error delimiter (error delimiter) or the first two bits of the interframe spacing (IFS), then the receiving node evaluates this as an overload condition (overload condition). The receiving node would therefore send an overload identifier, which can also be called an overload flag, onto the bus 40 although the sending node is still sending its frame 450 . Like an active error identifier 47 _A, the overload identifier has six dominant bits in a row.

Since the error cases mentioned cannot occur in the subscriber stations 10, 30, the communication on the bus 40 is not undesirably disturbed.

As a result, communication in the bus system can take place with a high degree of error tolerance and a high net data rate.

All previously described configurations of the subscriber stations 10, 20, 30, the bus system 1 and the method implemented therein can be used individually or in all possible combinations. In particular, everyone can Features of the exemplary embodiments described above and/or modifications thereof can be combined as desired. In addition or as an alternative, the following modifications in particular are conceivable.

Even if the invention has been 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 bus system 1 according to the exemplary embodiments can be a communication network in which data can be transmitted serially at two different bit rates. It is advantageous, but not an essential requirement, that in the bus system 1 exclusive, collision-free access by a subscriber station 10, 20, 30 to a common channel is guaranteed at least for certain periods of time.

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 the subscriber stations in the bus system 1 are of the same design, ie only subscriber station 10 or only subscriber station 30 are present.

Claims

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Expectations

1) Subscriber station (10; 20; 30) for a serial bus system (1), with a communication control device (11; 21; 31) for controlling communication between the subscriber station (10; 20; 30) and at least one other subscriber station (10; 20 ; 30) of the bus system (1) and for evaluating a signal (VDIFF) received from a bus (40) of the bus system (1), in which the bit time (t_btl) in a first communication phase (451) can differ from a bit time ( t_bt2) in a second communication phase (452), the communication control device (11; 21; 31) being designed to transmit the signal (VDIFF, RxD) received from the bus (40) and transmitted to a signal from another subscriber station (10; 20; 30) generated transmission signal (TxD), according to a predetermined frame (450) to sample and evaluate, wherein the communication control device (11; 21; 31) is configured to switch to an error passive reception mode (B_RX_P) if more than one predetermined number of errors learning occurs during communication on the bus (40), the communication control device (11; 21; 31) is configured to switch from the error passive reception mode (B_RX_P) to a re-integration mode (B_R) if the communication control device (11; 21; 31) detects an error in the signal (VDIFF , RxD), and wherein the communication control device (11; 21; 31) is designed to reintegrate itself into the communication on the bus (40) in the re-integration operating mode (B_R).

2) Subscriber station (10; 20; 30) according to claim 1, wherein the communication control device (11; 21; 31) is configured in the re-integration mode (B_R) on an edge in a predetermined field of the predetermined frame (450). ) Subscriber station (10; 20; 30) according to claim 1 or 2, wherein the communication control device (11; 21; 31) is configured to restart a search for an idle or ready condition each time in the re-integration mode (B_R), if the communication control device (11; 21; 31) has detected a falling edge in the signal (VDIFF, RxD) received from the bus (40). ) Subscriber station (10; 20; 30) according to one of the preceding claims, wherein the communication control device (11; 21; 31) is designed such that the communication control device (11; 21; 31) in the error passive reception mode (B_RX_P) no active error detection (47_A) may send onto the bus (40) if the communication control device (11; 21; 31) has detected an error during communication on the bus (40). ) Subscriber station (10; 20; 30) according to one of the preceding claims, wherein the communication control device (11; 21; 31) has an evaluation block (151) for evaluating the bus (40) received signal (VDIFF, RxD), and a Operating mode switching block (152) for switching the operating mode of the communication control device (11; 21; 31) on the basis of the evaluation carried out by the evaluation block (152). ) Subscriber station (10; 20; 30) according to any one of the preceding claims, also with a transmitting / receiving device (12; 32) for sending a transmission signal (TxD) on the bus (40) of the bus system (1) and / or for receiving a signal (VDIFF; RxD) from the bus (40) of the bus system (1). ) subscriber station (10; 20; 30) according to claim 6, wherein the communication control device (11; 21; 31) is designed to generate the transmission signal (TxD), and wherein the communication control device (11; 21; 31) is designed to transmit/receive device (12; 22; 32) by means of pulse width modulation in to signal the transmission signal (TxD) that the transceiver (12; 22; 32) changes its operating mode to an operating mode (B_451) for transmitting in the first communication phase (451) or to an operating mode (B_452_TX; B_452_RX) for transmitting in a second communication phase (452). ) Subscriber station (10; 30) according to any one of the preceding claims, wherein the subscriber station (10; 30) is a CAN XL subscriber station. ) Subscriber station (10; 30) according to any one of the preceding claims, wherein the predetermined frame (450) is constructed compatible with CAN FD. 0) subscriber station (20) according to any one of claims 1 to 6, wherein the subscriber station (20) is a CAN FD subscriber station. 1) Subscriber station (10; 20; 30) according to one of the preceding claims, wherein the communication control device (11; 21; 31) is configured to negotiate in the first communication phase (451) with the other subscriber stations (10; 20; 30) which of the subscriber stations (10, 20, 30) of the bus system (1) in the subsequent second communication phase (452) is given at least temporarily exclusive, collision-free access to the bus (40). 2) 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; 20; 30) is a subscriber station (10; 20; 30) according to any one of the preceding claims. ) Method for communication in a serial bus system (1), the method being carried out with a subscriber station (10; 20; 30) of the bus system (1) which has a communication control device (11; 21; 31), the method having the steps having,

Controlling, with a communication control device (11; 21; 31), communication between the subscriber station (10; 20; 30) and at least one other subscriber station (10; 20; 30) of the bus system (1) and evaluating one of a bus (40 ) of the bus system (1) received signal (VDIFF), in which the bit time (t_btl) in a first communication phase (451) can differ from a bit time (t_bt2) in a second communication phase (452), wherein the communication control device (11; 21 ; 31) samples and evaluates the signal (VDIFF, RxD) received from the bus (40), which is based on a transmission signal (TxD) generated by another subscriber station (10; 20; 30), according to a predetermined frame (450), wherein the communication control device (11; 21; 31) switches to an error passive reception mode (B_RX_P) if more than a predetermined number of errors occur in the communication on the bus (40), wherein the communication control device (11; 21; 31 ) vo n the error passive reception mode (B_RX_P) in a re-integration mode (B_R) switches when the communication control device (11; 21; 31) sensing an error in the signal (VDIFF, RxD) received from the bus (40), and wherein the communication control device (11; 21; 31) engages in the communication on the bus (40) in the re-integration mode (B_R) re-integrated.