Commander-subscriber station for a serial bus system, responder-subscriber station for a serial bus system and method for communication in a serial bus system

Abstract

The invention relates to a commander-subscriber station (100) for a serial bus system (1), a responder-subscriber station (101... 101N) for the serial bus system (1) and a method for communication in a serial bus system (1). The commander-subscriber station (100) has a communication control device (11) for controlling a communication of the subscriber station (100) and a responder-subscriber station (101; 102;... 101N) of the bus system (1) and for analysing at least one signal (VDIFF; RxD) received by a bus (40) of the bus system (1) using a frame (450; 460), 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), and a synchronisation module (15) for synchronising the communication control device (11) to the signal (VDIFF; RxD) received by the bus (40), wherein the synchronisation module (15) is designed to deactivate its synchronisation function if the bit time (t_bt1) of the first communication phase (451) of a specified frame (460) has a specified value corresponding to a bitrate which is greater than a specified bitrate, and if the communication control device (11) is intended to act as a sender of the specified frame (460) so that the commander-subscriber station (100) is the sender of the signal (VDIFF; RxD) received by the bus (40).

Description

[0001] Description

[0002] Commander station for a serial

[0003] Subscriber station for a serial and methods for communication in a serial

[0004] Technical area

[0005] The present invention relates to a commander subscriber station for a serial bus system, a responder subscriber station for a serial bus system and a method for communication in a serial bus system.

[0006] State of the art

[0007] Bus systems are used in many areas of technology for communication between technical devices, such as sensors and control units

[0008] It is known to use Classical CAN and / or CAN FD for communication between devices in vehicles and / or other technical equipment, both of which are standardized in the international standard ISO11898-1:2015.

[0009] The subscriber stations of such a bus system are also called nodes. Such subscriber stations have a microcontroller that supports all functions of the aforementioned Classical CAN and / or CAN FD standards.

[0010] In such bus systems, at least one subscriber station may be present, which only has to perform very simple functions, such as an indicator light, in particular a light-emitting diode (LED), which is to be switched on or off and / or changed color as required under the control of the microcontroller of another subscriber station. A sensor may also be present and controlled, which is to periodically deliver its detection data to the microcontroller of another subscriber station. Such subscriber stations for performing simple functions can also be referred to as responders. A subscriber station with the microcontroller controlling a responder is also referred to as a commander.

[0011] For a more cost-effective connection of responders to CAN bus systems, the specification for the CAN protocol variant "CAN FD Light" is currently being developed. "CAN FD Light" is also abbreviated to FDL and specifies communication between a commander and at least one responder. FDL communication should use frames without bit rate switching. FDL is currently specified in the document CiA 604-1 and is also planned to be included in the next version of ISO 11898-1.

[0012] FDL is intended for CAN bus systems in which a commander CAN subscriber station controls the function(s) of several responder CAN subscriber stations. FDL does not support arbitration. Therefore, the commander uses the "polling" principle to communicate with the responders. The commander is a control unit with a microcontroller running the application software. The microcontroller contains a CAN controller that can send and receive CAN FD frames according to ISO 11898-1:2015. Polling is also performed by sending a CAN FD frame.

[0013] Responders are application-specific integrated circuits, also called ASICs, that have an FDL controller. Responders have little or no local processing power and can perform simple functions, such as turning a light-emitting diode (LED) on / off or controlling the color of a light-emitting diode (LED), as previously described. A responder only sends a CAN FD frame when requested to do so by the commander via a transmit poll. Thus, upon receiving a transmit poll from the commander, the responder CAN subscriber stations (responders) send their functional information, such as a sensor value, via a CAN FD message to the commander CAN subscriber station (commander). To enable cost-effective integration of a responder on a single ASIC using a mixed semiconductor process, such as bipolar transistor(s), CMOS transistor(s), and DMOS transistor(s) (BCD technology), an FDL controller is integrated into a responder.The FDL controller is much simpler compared to a CAN FD controller.

[0014] This means that some functions of the CAN FD protocol, as specified in ISO 11898-1:2015, are omitted from the FDL specification. For example, fault confinement has been omitted. An error counter is provided for this purpose, and error frames are created and sent as needed. Furthermore, the responders are not designed to participate in CAN arbitration. The commander controls communication to avoid access conflicts on the CAN bus.

[0015] FDL communication uses only FBFF format frames, which use an 11-bit identifier and no bit rate switching. This saves additional ASCII space and facilitates clock recovery from the CAN bit stream, eliminating the need for a crystal oscillator in the responder.

[0016] The disadvantage is that currently, for commanders using a CAN controller according to ISO 11898-1:2015, bit rates higher than 2 Mbit / s are not possible for communication on the bus with the responders.

[0017] To enable higher bit rates at some point in the future, document CiA604-3 describes some commander functions that deviate from ISO 11898-1:2015. These functions include disabling bus monitoring, disabling the need for the commander to send an ACK response for a responder's message, and disabling the transmission of error frames and overload frames.

[0018] The problem, however, is that these functions are not sufficient to actually enable communication on the bus at bit rates higher than 2 Mbps, for example, up to 8 Mbps. Disclosure of the invention

[0019] Therefore, it is an object of the present invention to provide a commander subscriber station for a serial bus system, a responder subscriber station for a serial bus system, and a method for communication in a serial bus system that solve the aforementioned problems. In particular, a commander subscriber station for a serial bus system, a responder subscriber station for a serial bus system, and a method for communication in a serial bus system are to be provided, which enable communication in the serial bus system with high error robustness, at a higher bit rate than before, and with a high net data transmission rate.

[0020] This object is achieved by a commander subscriber station for a serial bus system having the features of claim 1. The commander subscriber station has a communication control device for controlling communication between the subscriber station and a responder subscriber station of the bus system and for evaluating at least one signal received from a bus of the bus system based on a frame in which the bit time in a first communication phase can differ from a bit time in a second communication phase, and a synchronization module for synchronizing the communication control device to the signal received from the bus, wherein the synchronization module is designed to deactivate its synchronization function if the bit time of the first communication phase of a predetermined frame has a predetermined value corresponding to a bit rate that is greater than a predetermined bit rate,and if the communication control device is to act as the transmitter of the predetermined frame, so that the commander subscriber station is the transmitter of the signal received from the bus.,

[0021] The described commander subscriber station can be used for FDL communication with a responder subscriber station at bit rates higher than currently possible. In particular, the bit rates are greater than 2 Mbit / s, and especially up to 8 Mbit / s. For bit rates up to 2 Mbit / s, an existing CAN controller and CAN transceiver in vehicles and / or other technical equipment specified for CAN FD according to the international standard ISO11898-1:2015 can be used. In particular, a CAN SIC transceiver can be used, enabling bit rates up to 8 Mbit / s.

[0022] The described commander station thus supports more than one frame format. The commander station can thus be configured to select a frame format from at least two different frame formats in which the next frame is to be sent on the bus. The described commander station can therefore specifically disable or enable its synchronization function for a predetermined frame or a frame in a predetermined frame format, as needed.

[0023] This means that the Commander subscriber station can also be used very advantageously in applications where data is to be exchanged between the Commander subscriber station and at least one Responder subscriber station connected via the bus in a shorter time than before.

[0024] Overall, the described subscriber station contributes to making the bus system more cost-effective, while still enabling robust and reliable CAN communication.

[0025] Advantageous further embodiments of the subscriber station are specified in the dependent claims.

[0026] The synchronization module may have a synchronization block configured to synchronize the communication control device to the signal received from the bus, and a configuration block storing a value for at least one synchronization configuration bit indicating whether the bit rate is greater than the predetermined bit rate. The synchronization module may also have an evaluation block for evaluating the value of the at least one configuration bit, and a switching block for enabling or disabling the synchronization of the synchronization block based on the evaluation of the evaluation block.

[0027] The commander subscriber station may be a CAN FD subscriber station, wherein the predetermined frame is a CAN FD frame in the FBFF format.

[0028] The predetermined bit rate can be 2 M bit / s.

[0029] The above-mentioned object is also achieved by a responder subscriber station for a serial bus system having the features of claim 6. The responder subscriber station has a communication control device for controlling communication of the subscriber station with a commander subscriber station of the bus system and for evaluating at least one signal received from a bus of the bus system based on a predetermined frame, in which the bit time in a first communication phase can differ from a bit time in a second communication phase, and a synchronization module for synchronizing the communication control device to the signal received from the bus, wherein the synchronization module is designed to switch off its synchronization function when the

[0030] Communication control device should act as the transmitter of the frame, so that the responder subscriber station is the transmitter of the signal received from the bus.

[0031] In the responder subscriber station, the synchronization module can be configured to deactivate its synchronization function when the bit time of the first communication phase of the predetermined frame has a predetermined value corresponding to a bit rate greater than a predetermined bit rate, and when the communication control device is to act as the transmitter of the frame, so that the responder subscriber station is the transmitter of the signal received from the bus. It is conceivable that the synchronization module comprises a synchronization block configured to synchronize the communication control device to the signal received from the bus, and a configuration block in which a value for at least one synchronization configuration bit is stored, indicating whether the bit rate is greater than the predetermined bit rate.

[0032] The synchronization module may also have an evaluation block for evaluating the value of the at least one configuration bit, and a switching block for switching the synchronization of the synchronization block on or off based on the evaluation of the evaluation block.

[0033] The responder subscriber station may be a subscriber station configured for communication according to CAN FD, wherein the predetermined frame is a CAN FD frame in the FBFF format.

[0034] Also with respect to the responder subscriber station, the predetermined bit rate may be 2 Mbil / s.

[0035] The previously described commander subscriber station and at least one previously described responder subscriber station can be part of a bus system having a bus and at least two subscriber stations which are connected to one another via the bus in such a way that they can communicate with one another serially, wherein each of the at least two subscriber stations also has a transmitting / receiving device for transmitting a transmitting signal to the bus of the bus system and / or for receiving a signal from the bus of the bus system.

[0036] The bus system may also have at least one third subscriber station configured to transmit and / or receive signals based on a frame, wherein the at least one third subscriber station has a communication control device configured to negotiate with the commander subscriber station in a first communication phase of the frame whether the third subscriber station or the commander subscriber station will receive at least temporarily exclusive, collision-free access to the bus in a subsequent second communication phase.

[0037] The above-mentioned object is also achieved by a method for communication in a serial bus system according to claim 14. The method is carried out with a previously described commander subscriber station and a previously described responder subscriber station.

[0038] The method offers the same advantages as previously mentioned with regard to the subscriber stations.

[0039] Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0040] Drawings

[0041] The invention is described in more detail below with reference to the accompanying drawings and exemplary embodiments. They show:

[0042] Fig. 1 is a simplified block diagram of a bus system according to a first embodiment;

[0043] Fig. 2 shows the format of CAN FD frames according to the aforementioned standard ISO11898-1:2015 for a message that can be sent by a transceiver for a subscriber station of the bus system according to the first embodiment;

[0044] Fig. 3 shows the format of CAN FD frames in FDL format, in particular FBFF format without bit rate switching, for a message that can be sent as an alternative to the CAN FD frame of Fig. 2 by a transceiver for a subscriber station of the bus system according to the first embodiment; Fig. 4 shows a simplified schematic block diagram of a first subscriber station (commander) of the bus system according to the first embodiment;

[0045] Fig. 5 shows a time profile of a digital transmission signal during operation of the bus system at the first subscriber station, which is connected to the same bus of the bus system with at least one second subscriber station;

[0046] Fig. 6 shows a time course of bus signals CAN_H and CAN_L at the first subscriber station according to the first embodiment;

[0047] Fig. 7 shows a time profile of a differential voltage VDIFF of the bus signals CAN_H and CAN_L at the first subscriber station according to the first embodiment;

[0048] Fig. 8 shows a time profile of a digital receive signal that the first or a second subscriber station generates from a signal received from the bus, which is based on the transmit signal of the first subscriber station; and

[0049] Fig. 9 is a simplified schematic block diagram of a second subscriber station (responder) of the bus system according to the first embodiment.

[0050] In the figures, identical or functionally equivalent elements are provided with the same reference numerals unless otherwise indicated.

[0051] Description of the embodiments

[0052] Fig. 1 shows as an example a bus system 1 which is designed in particular fundamentally for a CAN bus system, a CAN FD bus system, and / or modifications thereof, as described below. The bus system 1 can be used in a vehicle, in particular a motor vehicle, an aircraft, etc., or in a hospital, etc. In Fig. 1, the bus system 1 has a bus 40, to which a commander subscriber station 100 and several responder subscriber station(s) 101, 102, 103 ... 10N are connected. N is a natural number greater than or equal to 1. 1 to N responder subscriber stations 101, 102, 103 ... 10N can be connected to the bus 40. The bus 40 can have a first bus wire 41 (Fig. 4) and a second bus wire 42 (Fig. 4), which are not shown in Fig. 1. The bus wires can also be called CAN_H and CAN_L and are used for electrical signal transmission after coupling of the dominant levels or.Generation of recessive levels or other levels for a signal in the transmit state.

[0053] The commander subscriber station 100 is, for example, a control unit of a motor vehicle or other technical system, as described in more detail below. The responder subscriber stations 101, 102, 103 ... 10N can, for example, have at least one sensor, at least one display device, at least one actuator, at least one transmitter, etc. of a motor vehicle or other technical system, as described in more detail below.

[0054] As shown in Fig. 1, the commander subscriber station 100 has a communication control device 11, a transmitting / receiving device 12 and a synchronization module 15. Each of the responder subscriber stations 101, 102, 103 ... 10N has a communication control device 21, a transmitting / receiving device 22 and a synchronization module 25. The transmitting / receiving devices 12, 22 of the subscriber stations 101 ... 10N are each directly connected to the bus 40, even if this is not illustrated in Fig. 1.

[0055] The commander subscriber station 100 is configured to create messages 45, 46 in the form of signals. However, the commander subscriber station 100 is configured to send only messages 46 in the form of signals to one of the subscriber stations 101 ... 10N via the bus 40. The message 46 is largely structured in the same way as a message 45, as described in more detail with reference to Fig. 2 and Fig. 3. The subscriber stations 101 ... 10N in Fig. 1 are configured to create messages 46 in the form of signals and send them to the commander subscriber station 100 via the bus 40. The messages 46 are serially transmittable between the subscriber station 100 and one of the subscriber stations 101 to 10N.

[0056] The communication control devices 11, 21 each serve to control communication between the subscriber station 100 via the bus 40 and one of the subscriber stations 101...10N. The communication control devices 11, 21 generate a transmit signal TxD as needed, which is described in more detail below with reference to Fig. 5. Furthermore, the communication control devices 11, 21, 31 read or decode a receive signal RxD, which is described in more detail below with reference to Fig. 8.

[0057] The communication control device 11 can be designed, at least in part, like a conventional CAN controller according to ISO 11898-1:2015, i.e., like a CAN FD controller or a CAN FD-tolerant Classical CAN controller. The CAN FD messages 45 can contain from 0 to 64 data bytes, which are also transmitted at a significantly faster data rate than a Classical CAN message.

[0058] The communication control device 11 is designed to provide a CAN FD message 45, 46 or to receive an FDL message 46 from the subscriber station 101 ... 101 N as needed. The respective synchronization modules 15, 25 are used to send and receive the FDL message 46. The FDL message 46 is structured based on an FDL format, which is described in more detail with reference to Fig. 3.

[0059] The communication control device 11 thus creates and reads a first message 45 or a second message 46, wherein the first and second messages 45, 46 differ in their data transmission standard, namely CAN FD and FDL in this case. As already mentioned previously with regard to the prior art, FDL communication uses, in particular, only frames without bit rate switching. Furthermore, FDL communication does not perform arbitration, in which the arbitration phase of message 45 negotiates which subscriber station has exclusive access to bus 40 in the following data phase.

[0060] The communication control device 21 is designed as an FDL controller. The synchronization module 25 is also present, which has functions compatible with the functions of the synchronization module 15. The communication control device 21 creates second messages 46, for example, FDL messages 46, and is configured to read messages 45, 46.

[0061] To communicate with one of the subscriber stations 101 ... 100 N, the subscriber station 100 sends a transmit poll to the desired subscriber station 101 ... 100 N via the bus 40. The transmit poll is carried out by sending a message 46 based on an FDL frame shown in Fig. 3. A responder subscriber station 101 ... 100 N only sends a message 46 based on an FDL frame according to Fig. 3 via the bus 40 to the commander subscriber station 100 if the subscriber station 100 has requested the subscriber station 101 ... 100 N to do so by means of a transmit poll.

[0062] Thus, subscriber station 100 functions as a commander / queryer, and subscriber stations 101 ... 101 N function as a responder. Therefore, subscriber station 100 is hereinafter referred to as the FDL commander and subscriber stations 101 ... 101 N as the FDL responder.

[0063] Fig. 2 shows a frame 450, which can be created by the subscriber station 100, for a message 45 with up to 64 data bytes in CAN FD FEFF format. The CAN FD frame 450 can be provided by the communication control device 11, namely encoded in a digital transmission signal TxD, for the associated transceiver device 12 for transmission on the bus 40 to another CAN FD subscriber station (not shown).

[0064] Frame 450 is divided into two communication phases, called the arbitration phase 451 (first communication phase) and the data phase 452 (second communication phase). Frame 450 begins and ends in the arbitration phase 451. Frame 450 begins with an SOF bit and has an arbitration field 453, a control field 454, a data field 455, a checksum field 456, an acknowledgement field 457 (ACK), and an end-of-frame field EOF.

[0065] Bits in the arbitration phase 451 of the frame 450 may have a longer bit time than bits of the data phase 452, as illustrated by way of example in Fig. 2. The switching from the bits with the bit time of the arbitration phase 451 to the bits with the bit time of the data phase 452 occurs in a BRS bit, as indicated by SP in Fig. 2.

[0066] Bits represented by a thick line along their lower line in Fig. 2 are transmitted as dominant, or '0', in frame 450. Bits represented by a thick line along their upper line in Fig. 2 are transmitted as recessive, or '1', in frame 450. Such bits, represented by a thick line in Fig. 2, have a predetermined fixed or specified value in frame 450.

[0067] The arbitration field 453 includes an identifier of the frame 450 in the base-ID field and the ID-ext field. The identifier has 29 bits. An SRR bit and an IDE bit are provided between the base-ID field and the ID-ext field. An RRS bit is located at the end of the arbitration field 453. Fig. 2 shows the FEFF format with the 29-bit "Extended Identifier."

[0068] The control field 454 begins with an FDF bit, followed by a res bit. This is followed by the BRS bit and an ESI bit. The ESI bit is therefore the first bit in frame 450 with the bit time of data phase 452.

[0069] The control field 454 ends with a DLC field encoding the length of the following data field 455. The res bit must be sent for frame 450 with a logical value of 0, in other words, dominant. The data field 455 is not present if the DLC field of the control field 453 has the value 0. The data field 455 has a length corresponding to the value encoded in the DLC field. This value can be up to 64 bytes, as previously mentioned.

[0070] The checksum field 456 contains, in an SBC field, the number of stuff bits modulo 8 that were inserted into the frame 450 according to the bit stuffing rule, namely, after every five identical bits, an inverse bit is inserted. In addition, the checksum field 456 contains a CRC checksum in a CRC field, which can also be called a CRC checksum, and ends with a subsequent CRC delimiter CRC-Del.

[0071] The switching from the bits with the bit time of the data phase 452 to the bits with the bit time of the arbitration phase 451 takes place in the bit CRC-Del, as marked SP in Fig. 2.

[0072] The acknowledgement field 457 contains an ACK bit slot, in which subscriber stations that are currently only receivers of frame 450 but not senders of the frame can confirm or not confirm the correct reception of frame 450 from bus 40. The acknowledgement field 457 ends with an ACK-Del bit, also called an ACK delimiter.

[0073] The end-of-frame field (EOF) contains a bit sequence that marks the end of frame 450. The end-of-frame field (EOF) thus serves to mark the end of frame 450. The end-of-frame field (EOF), together with the ACK delimiter, ensures that a number of 8 recessive bits are sent at the end of frame 450. This is a bit sequence that cannot occur within frame 450. This allows the subscriber stations 100, 101, ... 10N to reliably detect the end of frame 450.

[0074] After the end of frame (EOF), which has 7 bits, frame 450 is followed by an interframe space (IFS), which is not shown in Fig. 2. This interframe space (IFS) in CAN FD is designed according to ISO 11898-1:2015. The interframe space (IFS) has at least 3 bits. Otherwise, the fields and bits mentioned are known from ISO 11898-1:2015 and are therefore not described in detail here.

[0075] In the arbitration phase 451 of CAN FD, the identifier (ID), for example, with bits ID28 to ID18 in the arbitration field 453, is used to negotiate bit by bit between subscriber stations 100 or other CAN FD subscriber stations on bus 40 which subscriber station 100 wishes to send message 45 with the highest priority and therefore receives exclusive access to bus 40 of bus system 1 for the next transmission time 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). Subscriber stations 101 ... 10N, as FDL responder subscriber stations, do not support arbitration, as previously mentioned and as described in more detail below.

[0076] To avoid CAN arbitration, in which the well-known CSMA / CR procedure resolves a collision if two CAN nodes (subscriber stations) initiate a message at the same time, the commander must specify when which responder may send a message. This means that if the commander has requested a specific responder to send via a poll, the commander waits until the responder has responded before sending any other message. If a responder that has received a poll but has not yet started its response sees the start of another message on the CAN bus 40, it considers its poll to be completed and does not start its message 46. The document CiA604-1 specifies the earliest possible time at which a responder may respond to the poll with a message. This start of transmission can be delayed if the responder needs more time to prepare the transmission data.The response times of the various responders in the CAN system are known to the Commander.

[0077] Collisions between FDL responders (subscriber stations 101 ... 10N) and the commander (subscriber station 100) or any other CAN FD nodes (e.g., subscriber stations 100) that contain the arbitration function can also be avoided by assigning the responders identifiers with a higher arbitration priority for transmission. This means that if the other nodes initiate a message at the same time as a responder, they lose the arbitration and become the receiver.

[0078] The subscriber station 100, as the sender of a message 45, 46, begins sending bits of the data phase 452 to the bus 40 only when the subscriber station 100, as the sender, has won the arbitration and the subscriber station 100, as the sender, thus has exclusive access to the bus 40 of the bus system 1 for sending. The same applies to each CAN FD subscriber station 10 that is connected to the bus 40 and wishes to send a message 45, 46 to the bus 40.

[0079] Fig. 3 shows an FDL frame 460 for message 46, as provided by a subscriber station (responder) 101 ... 10N or its communication control device 21, namely encoded in a digital transmission signal TxD, for the associated transceiver 22 for transmission on bus 40. In this embodiment, the communication control device 21 creates frame 460 as compatible with CAN FD, as also illustrated in Fig. 3.

[0080] According to Fig. 3, the FDL frame 460 for CAN communication on the bus 40 is also divided into different communication phases 451, 452, namely the arbitration phase 451 and the data phase 452. After a start bit (SOF), the frame 460 has an arbitration field 463, a control field 464, a data field 465, a checksum field 466, and an acknowledgment field 467. This is followed by the end of frame field EOF, as in a frame 450 according to Fig. 2.

[0081] The FDL format corresponds to the FBFF format from ISO11898-1:2015. In this format, the sender can decide whether to set the BRS bit to 1 or 0, where BRS = Bit Rate Switch. If the BRS bit is set to 1, the bit rate is increased or the bit time is shortened in the data phase 452. If the BRS bit is set to 0, the bit rate or bit time is the same in both communication phases 451, 452. In FDL, it is currently intended that the bit rate is not switched within frame 460. Therefore, BRS=0 is sent. In this case, the commander (subscriber station 100) must set the BRS bit to 0 in a message 46 to the responder (one of the subscriber stations 101 ... 10N) so that the responder understands it.

[0082] However, in the arbitration phase 451, in an FDL communication with a frame 460, the responder does not perform the arbitration described above with reference to Fig. 2. Instead, the communication control device 21 is configured as an FDL responder to write the identifier (ID) assigned to the responder into the frame 460. For example, if the subscriber station 101 (responder) receives a send request from the subscriber station 100 (commander), the subscriber station 101 sends an FDL frame 460 according to Fig. 3 or a message 46 via the bus 40 to the subscriber station 100. In CAN communication and with FDL, the identifiers (ID) are sender addresses or content information, but not recipient addresses. Each identifier may only be sent by a predetermined subscriber station 100 to 10N so that the commander can recognize the respective sender.If a subscriber station can send 100 to 10N different data packets, this subscriber station, and only this subscriber station, may use different identifiers (IDs) to send this data. However, for simplicity, the commander could poll the responders with different identifiers (IDs). Alternatively, the commander could poll the responders with a frame 460 containing a common query identifier (ID) and then encode the intended responder in data field 465 within this frame 460. The intended responder then responds, each using its own identifier (ID).

[0083] When switching to the data phase 452, no bit rate switching takes place in frame 460. This means that the bit time of bits in the arbitration phase 451 and the data phase 452 is the same. However, it is possible that the bit time in the first communication phase (arbitration phase) 451 may differ from the bit time in the second communication phase (data phase) 452. In the data phase 452, in addition to part of the control field 464 of the frame 460, the payload of the FDL frame 460 or the message 46 from the data field 465 and the checksum field 466 are sent. At the end of the checksum field 466 or before the confirmation field 467, the transition from the data phase 452 back to the arbitration phase 451 takes place, as shown in Fig. 3.

[0084] As shown in Fig. 3, the respective subscriber station 101 ... 10N partially uses, in particular up to and including the FDF bit, a format known from CAN / CAN-FD according to ISO11898-1:2015, as shown in Fig. 2 in the arbitration phase 451 as the first communication phase. In contrast, the respective subscriber station 101 uses an FDL format, described below, starting with the FDF bit in the first communication phase and in the data phase 452 as the second communication phase. As with CAN FD, recessive and dominant levels are used in the FDL data phase 452 for transmission on bus 40.

[0085] In general, two different stuffing rules are applied when generating frame 460. Up to the FDF bit in the arbitration field 463, the dynamic bit stuffing rule of CAN FD, or for a frame 450 of Fig. 2, applies, so that an inverse stuff bit is inserted after every five identical bits in a row. In the data phase 452 up to the SBC field, a fixed stuffing rule applies, so that a fixed stuff bit is inserted after a fixed number of bits. Alternatively, two or more bits can be inserted as fixed stuff bits instead of just one.

[0086] The DLC field and the data field 465 are configured as previously described for Fig. 2. In particular, the data field 465 has a length of 0 bytes when the DLC field of the control field 463 has the value 0.

[0087] After the data field 465, the checksum field 466 follows in the frame 460, which is structured as in CAN FD, as shown in Fig. 2.

[0088] This is followed by the acknowledgment field 467, which is structured as in CAN FD, as shown in Fig. 2. The acknowledgment field 467 contains an ACK slot bit, in which subscriber stations that are currently only receivers of frame 460 but not senders of the frame can confirm or not confirm the correct reception of frame 460 from bus 40. The acknowledgment field 467 ends with an ACK-Del bit, also called an ACK delimiter.

[0089] After the confirmation field 467, the end field (EOF = End of Frame) follows in the frame 460, as in CAN FD according to Fig. 2.

[0090] The end of field (EOF) is 7 recessive bits long.

[0091] Following the end of field (EOF) in frame 460 is an inter-frame space (IFS), as previously explained with respect to frame 450 of Fig. 2.

[0092] Fig. 4 shows the basic structure of the subscriber station 100 with the communication control device 11, the transmitting / receiving device 12 and the synchronization module 15, which is part of the communication control device 11.

[0093] According to Fig. 4, in addition to the communication control device 11 and the transceiver device 12, the subscriber station 100 has a microcontroller 13, to which the communication control device 11 is assigned, and a system ASIC 16 (ASIC = Application-Specific Integrated Circuit), which can alternatively be a system base chip (SBC) on which several functions necessary for an electronic assembly of the subscriber station 100 are combined. The system ASIC 16 has, in particular, an application 161, which can be designed as a computer program (app) or software. Such an application is a technical application 161. The application 161 is, for example, any application in a vehicle. In particular, the application is a windshield washer system and / or a driver assistance system, etc.For example, the windshield washer system controls the movement of at least one windshield wiper (actuator) using data from a rain sensor and / or wind sensor and / or speed sensor and / or light sensor, and / or a warning light (actuator) can be turned on or off. However, the application is not limited to a windshield washer system or parts thereof.

[0094] In addition to the transmitting / receiving device 12, a power supply device 17 is installed in the system ASIC 16, which supplies the transmitting / receiving device 12 with electrical energy. The power supply device 17 typically supplies a CAN_Supply voltage of 5 V. However, depending on requirements, the power supply device 17 can supply a different voltage with a different value. Additionally or alternatively, the power supply device 17 can be configured as a current source.

[0095] If the communication control device 11 acts as an FDL commander, the communication control device 11 may create a frame 460 in which no bit rate switching / bit rate change occurs and / or evaluate such a frame 460.

[0096] The synchronization module 15 has a synchronization block 151, a configuration block 152, an evaluation block 153, and a switching block 154. In particular, a value for at least one synchronization configuration bit 1521 can be stored in the configuration block 152. The synchronization block 151 can be the bit timing control unit BTL of the communication control device 11.

[0097] The synchronization module 15, in particular the evaluation block 153 and the switching block 154, can be implemented at least partially as software.

[0098] Synchronization block 151 has a synchronization function described in ISO 11898-1:2015 and the FDL specification according to CiA document CiA604-3. However, this synchronization function can be switched on as needed, as described in more detail below.

[0099] In addition to the synchronization module 16, the transmitting / receiving device 12 also has a transmitting module 121 and a receiving module 122. Although the following always refers to the transmitting / receiving device 12, it is alternatively possible to provide the receiving module 122 in a separate device external to the transmitting module 121. The transmitting module 121 and the receiving module 122 can be constructed as in a conventional transmitting / receiving device 22. The transmitting module 121 can, in particular, have at least one operational amplifier and / or one transistor. The receiving module 122 can, in particular, have at least one operational amplifier and / or one transistor.

[0100] The transceiver device 12 is connected to the bus 40, more precisely to its first bus wire 41 for CAN_H and its second bus wire 42 for CAN_L. The voltage supply for the power supply device 17 for supplying the first and second bus wires 41, 42 with electrical energy, in particular the CAN supply voltage, is provided via at least one terminal 43. The connection to ground or CAN_GND is realized via a terminal 44. The first and second bus wires 41, 42 are terminated with a terminating resistor 49.

[0101] The first and second bus wires 41, 42 are connected in the transmitting / receiving device 12 not only to the transmitting module 121, which is also referred to as transmitter, but also to the receiving module 122, which is also referred to as receiver, even if the connection is not shown in Fig. 4 for simplification.

[0102] During operation of the bus system 1, the transmitting module 121 of Fig. 4 can serially convert a transmitting signal TxD of the communication control device 11 into corresponding signals CAN_H, CAN_L for CAN or CAN FD for the bus wires 41, 42 and transmit these signals to the terminals for CAN_H and CAN_L on the bus 40. The communication control device 11 transmits the transmitting signal TxD of Fig. 5 over time t (serially) via terminals TXD to the transmitting module 121, as shown in Fig. 4. As shown as an example in Fig. 5, the transmit signal TxD has the voltage states H (High) and L (Low) with a corresponding voltage U. According to the example of Fig. 6, the signals CAN_H and CAN_L in the arbitration phase 451 have the dominant and recessive bus levels 401, 402, as known from CAN. On the bus 40, a difference signal VDIFF = CAN_H - CAN_L is formed, which is shown in Fig. 7 for the arbitration phase 451.The individual bits of the VDIFF signal with the bit time t_bt1 can be detected in the arbitration phase 451 and the data phase 452 with a reception threshold T_a of, for example, 0.7 V. In the data phase 452 of a frame 450, the bits of the CAN_H and CAN_L signals can be transmitted faster, i.e., with a shorter bit time t_bt2, than in the arbitration phase 451, as previously mentioned. Thus, in CAN FD for the frame 450, the CAN_H and CAN_L signals differ from the conventional CAN_H and CAN_L signals in the data phase 452 at least in their faster bit rate.

[0103] The sequence of states H, L of the transmit signal TxD in Fig. 5 and the resulting states 401, 402 for the signals CAN_H, CAN_L in Fig. 6, as well as the resulting waveform of the voltage VDIFF in Fig. 7, serve only to illustrate the function of the subscriber station 100. The sequence of data states for the bus states 401, 402 can be selected as required.

[0104] The receiving module 122 forms a received signal RxD from the signals CAN_H and CAN_L received from the bus 40, which are shown in Fig. 6, or the differential voltage VDIFF of Fig. 7. To generate the digital received signal RxD of Fig. 8, the receiving module 122 samples the signal VDIFF received from the bus 40 or at least one of the signals CAN_H, CAN_L at sampling points AP according to Fig. 6 or Fig. 7, as known. The received signal RxD is shown in Fig. 8 without any propagation delay. The receiving module 122 forwards this received signal RxD to the associated communication control device 11, as shown in Fig. 4.

[0105] For a message 46 based on a frame 460, the signals from Fig. 5 to Fig. 8 apply accordingly.

[0106] During operation of bus system 1, subscriber station 100 (commander), more precisely, communication control device 11, performs bus monitoring. According to ISO 11898-1:2015, subscriber station 100, in particular communication control device 11, compares its own transmitted bits at the sample point AP according to a frame 450, 460 and a transmitted signal TxD (Fig. 5) with the bits observed on bus 40 according to the received signal RxD (Fig. 8). A difference is considered an error, except for arbitration and the ACK bit.

[0107] However, according to document CiA604-3, the subscriber station 100 (commander), or more precisely the communication control device 11, switches off bus monitoring for short bit times t_bt1, t_bt2. In particular, the bit times t_bt1, t_bt2 are the same, as previously described. Such shorter bit times occur at higher bit rates above 2 Mbit / s, at which the so-called loop delay of the subscriber station 100 (CAN node) is in the range of a bit time t_bt1, t_bt2 or more. The so-called loop delay indicates the time that elapses until the subscriber station 100 can internally recognize the bit of the transmit signal TxD sent via the TXD port as a bit of the receive signal RxD sent via the RXD port.

[0108] In addition, the subscriber station 100 (commander), more precisely the communication control device 11, performs a synchronization function for all frames 450, 460 that have bits with a bit time t_bt1, t_bt2 for bit rates up to 2 Mbil / s during operation of the bus system 1 with the synchronization block 151.

[0109] The synchronization block 151 observes the edges from recessive to dominant or vice versa, i.e. a change between the states 401, 402 or 402, 401 in Fig. 6 or Fig. 7. The synchronization block 151 uses the observed edges to synchronize the position of the sampling point AP (sample point) within a bit time t_bt1, t_bt2. A receiver thus synchronizes itself to the transmitter of a frame 450, 460. If an edge ideally occurs at the beginning of a bit time t_bt1, t_bt2, no synchronization is necessary. If an edge occurs between the beginning of a bit time t_bt1, t_bt2 and the sampling point, a so-called late edge (“late edge”) occurs. This causes a synchronization in which the current bit time t_bt1, t_bt2 is extended. If an edge occurs between the sampling point AP (sample point) and the end of a bit time t_bt1, t_bt2, a so-called early edge occurs.This causes a synchronization in which the current bit time t_bt1 , t_bt2 is shortened.

[0110] According to ISO 11898-1:2015 and the FDL specification according to CiA 604-3, which refers to ISO, the transmitters of a frame 450, 460 also synchronize. However, the restriction applies that a subscriber station 100 that transmits a dominant bit does not synchronize to late edges. The reason for this is that the sender sees all of the bits it transmits late due to the loop delay. Therefore, synchronization to these late edges would lengthen these bits and corrupt the bit rate. The permitted synchronization to early edges stabilizes CAN arbitration at the beginning of frame 450, 460. Synchronization to the ACK edge, at which the sender transmits a recessive bit, synchronizes all subscriber stations in bus system 1 to the same edge.

[0111] The synchronization function is described in more detail in ISO 11898-1:2015 and the FDL specification according to the CiA document CiA604-3.

[0112] However, with the synchronization module 15, the synchronization function of the synchronization block 151 can be switched as required, as described below.

[0113] Evaluation block 153 is configured to evaluate synchronization configuration bit 1521 in configuration block 152. Synchronization configuration bit 1521 is set when subscriber station 100 (commander), more precisely, communication control device 11, is to transmit frame 450 or 460 with a bit time t_bt1 of the first communication phase 451 that corresponds to a bit rate greater than a predetermined bit rate. The predetermined bit rate is, in particular, greater than 2 Mbps.

[0114] If the evaluation of evaluation block 153 shows that synchronization configuration bit 1521 is set, evaluation block 153 checks whether subscriber station 100 (commander), more precisely, communication control device 11, should (currently) act as a transmitter, i.e., send a frame 460 to a responder on bus 40. Synchronization configuration bit 1521 is set, for example, together with the bit rate configuration, either via software or hard-wired. During operation of bus system 1, the bit is then constant.

[0115] If the evaluation of evaluation block 153 indicates that subscriber station 100 (commander), more precisely, communication control device 11, should act as a transmitter and send a frame 460 to a responder on bus 40, evaluation block 151 instructs switching block 154 to deactivate synchronization block 151. Switching block 154 thus deactivates or disables synchronization block 151 and thus its previously described synchronization function for all bits of frame 460 to be sent by subscriber station 100 as commander on bus 40, up to the last bit of the end of frame (EOF).

[0116] Disabling synchronization block 151 prevents the transmitter from synchronizing itself to its own transmitted edges, which it sees not within the transmitted bit but in one of the subsequent bit times. As a result, synchronization cannot cause reception errors in the other subscriber stations 101 ... 10N of the bus system.

[0117] After the last bit of the end of field (EOF) of the transmitted frame, the switching block 154 of Fig. 4 switches the synchronization block 151 and thus its previously described synchronization function back on.

[0118] According to Fig. 9, in addition to the communication control device 21 and the transceiver device 22, the responder subscriber station 101 has a simple control unit (FSM) or optionally a microcontroller 23, to which the communication control device 21 is assigned, and a system ASIC 26 (ASIC = Application Specific Integrated Circuit), which can alternatively be a system base chip (SBC) on which several functions necessary for an electronic module of the subscriber station 101 are combined. The system ASIC 26 has, in particular, an application 261, which can be designed as a computer program (app). Such an application is a technical application 261. The application 261 is, for example, a control for a sensor or a transmitter or an actuator or the like, which is controlled by the application 161 (Fig. 4) of the commander subscriber station 100 or is intended to provide data for the application 161.

[0119] In addition to the transmitting / receiving device 22, a power supply device 27 is installed in the system ASIC 26, which supplies the transmitting / receiving device 22 with electrical energy. The power supply device 27 typically supplies a CAN_Supply voltage of 5 V. However, depending on requirements, the power supply device 27 can supply a different voltage with a different value. Additionally or alternatively, the power supply device 27 can be configured as a current source.

[0120] The communication control device 21 creates a frame 460 in which no bit rate switching or bit rate change occurs, and / or evaluates such a frame 460 based on the frame 460 received from the commander subscriber station 100. The communication control device 21 can also be referred to as an FDL responder. The devices 21, 22 can only transmit such a frame 460 to the bus 40 upon request from the commander subscriber station 100 (polling).

[0121] The transmit module 222 of Fig. 9 is otherwise constructed in the same manner as previously described for the transmit module 122 of Fig. 4.

[0122] The synchronization module 25 of Fig. 9 has a synchronization block 251, a configuration block 252, an evaluation block 253 and a switching block 253. At least one configuration bit 2521, 2522 is stored in the configuration block 252.

[0123] The synchronization module 25 can also deactivate the synchronization for frames 460 or messages 46 sent by the subscriber station 101, as previously described with reference to Fig. 4 for the synchronization module 15 for frames 450, 460. Accordingly, the synchronization module 25 always deactivates the synchronization for frames 460 or messages 46 sent by the subscriber station 101 at high bit rates. The high bit rates are, for example, greater than 2 Mbit / s. In contrast to the synchronization module 15 of Fig. 4, the synchronization module 25 of Fig. 9 is optionally configured to deactivate the synchronization for frames 460 or messages 46 sent by the subscriber station 101 in the associated responder even at low bit rates, if desired. For this purpose, an additional configuration bit 2522 can be set, for example. For example, low bit rates are less than or equal to 2 Mbps.This shutdown does not have a major impact on the communication between Commander subscriber station 100 and the respective Responder subscriber station 101 ... 10N.

[0124] This makes it possible to select that the synchronization module 25 of Fig. 9 is optionally configured to deactivate its synchronization function for frames 460 or messages 46 transmitted by the subscriber station 101 at both a low and a high bit rate, i.e., regardless of the bit rate. In other words, this makes it possible to select that the synchronization module 25 of Fig. 9 is configured to deactivate its synchronization function for frames 460 or messages 46 transmitted by the subscriber station 101, regardless of the bit rate.

[0125] The subscriber stations 101 ... 10N can do without this synchronization because no arbitration takes place with FDL and no ACK bit is sent at higher bit rates.

[0126] The synchronization module 25 is otherwise constructed in the same way as previously described for the synchronization module 15.

[0127] The synchronization modules 15, 25 thus ensure that communication with CAN FD Light or FDL is possible even at bit rates greater than or equal to 2 Mbit / s.

[0128] All previously described embodiments of the subscriber stations 100, 101 ... 10N, of the bus system 1, and of the method implemented therein can be used individually or in all possible combinations. In particular, all features of the previously described embodiments and / or modifications thereof can be combined as desired. Additionally or alternatively, the following modifications are conceivable.

[0129] Even though 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 generated for the different communication phases can differ.

[0130] In particular, bus system 1 according to the exemplary embodiments can be a communications network in which data can be transmitted serially at two different bit rates. It is advantageous, but not a mandatory requirement, that exclusive, collision-free access of a subscriber station 100, 101 ... 10N to a common channel is guaranteed in bus system 1, at least for certain time periods.

[0131] The number and arrangement of the subscriber stations 100, 101 ... 10N in the bus system 1 of the exemplary embodiments is arbitrary. It is possible for one or more of the subscriber stations 100 to be present in the bus system 1. It is possible for more than one subscriber station 100 to be present in the bus system 1, to which at least one subscriber station 101 ... 10N is assigned, as previously described. In order not to disrupt the arbitration between the subscriber stations 100 on the bus 40, messages 46 from subscriber stations 101 ... 10N (responders) therefore have an identifier (ID) with a higher priority than the identifier(s) (ID) of the subscriber station 100 or of another CAN FD subscriber station.

[0132] In particular, only one subscriber station 100 (commander) and at least one subscriber station 101 ...10N (responder) are present, as shown in Fig. 1.

[0133] It is conceivable that in the subscriber station 100, the module 15 is arranged separately from the communication control device 11. It is conceivable that in at least one of the subscriber stations 100, 101 ... 10N, the module 25 is arranged separately from the communication control device 21.

Claims

Claims 1) Commander subscriber station (100) for a serial bus system (1), with a communication control device (11) for controlling communication between the subscriber station (100) and a responder subscriber station (101; 102; ... 101 N) of the bus system (1) and for evaluating at least one signal (VDIFF; RxD) received from a bus (40) of the bus system (1) on the basis of a frame (450; 460), 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), and a synchronization module (15) for synchronizing the communication control device (11) with the signal (VDIFF;RxD), wherein the synchronization module (15) is designed to switch off its synchronization function when the bit time (t_bt1) of the first communication phase (451) of a predetermined frame (460) has a predetermined value corresponding to a bit rate that is greater than a predetermined bit rate, and when the communication control device (11) is to act as a transmitter of the predetermined frame (460), so that the commander subscriber station (100) is the transmitter of the signal (VDIFF; RxD) received from the bus (40); 2) Commander subscriber station (100) according to claim 1, wherein the synchronization module (15) comprises a synchronization block (151) which is designed to synchronize the communication control device (11) to the signal (VDIFF; RxD) received from the bus (40), and a configuration block (152) storing a value for at least one synchronization configuration bit (1521) indicating whether the bit rate is greater than the predetermined bit rate. 3) Commander subscriber station (100) according to claim 2, wherein the synchronization module (15) further comprises an evaluation block (153) for evaluating the value of the at least one configuration bit (1521), and a switching block (154) for switching on or off the synchronization of the synchronization block (151) on the basis of the evaluation of the evaluation block (153). 4) Commander subscriber station (100) according to one of the preceding claims, wherein the commander subscriber station (100) is a CAN FD subscriber station, wherein the predetermined frame (460) is a CAN FD frame in the FBFF format. 5) Commander subscriber station (100) according to one of the preceding claims, wherein the predetermined bit rate is 2 Mbil / s. 6) Responder subscriber station (101; 102; ... 101 N) for a serial bus system (1), with a communication control device (21) for controlling communication between the subscriber station (101; 102; ... 101 N) and a commander subscriber station (100) of the bus system (1) and for evaluating at least one signal (VDIFF; RxD) received from a bus (40) of the bus system (1) based on a predetermined frame (460), 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), and a synchronization module (25) for synchronizing the communication control device (21) with the signal (VDIFF; RxD) received from the bus (40), wherein the synchronization module (25) is designed to switch off its synchronization function when the communication control device (21) is to act as a transmitter of the frame (460), so that the responder subscriber station (101; 102; ... 101 N) is the transmitter of the signal (VDIFF; RxD) received from the bus (40). 7) Responder subscriber station (101; 102; ... 101 N) according to claim 6, wherein the synchronization module (25) is designed to switch off its synchronization function when the bit time (t_bt1) of the first communication phase (451) of the predetermined frame (460) has a predetermined value corresponding to a bit rate that is greater than a predetermined bit rate, and when the communication control device (21) is to act as a transmitter of the frame (460), so that the responder subscriber station (101; 102; ... 101 N) is the transmitter of the signal (VDIFF; RxD) received from the bus (40). 8) Responder subscriber station (101; 102; ... 101 N) according to claim 7, wherein the synchronization module (25) comprises a synchronization block (251) designed to synchronize the communication control device (21) to the signal (VDIFF; RxD) received from the bus (40), and a configuration block (252) in which a value for at least one synchronization configuration bit (2521) is stored, which indicates whether the bit rate is greater than the predetermined bit rate. 9) Responder subscriber station (101; 102; ... 101 N) according to claim 7 or 8, wherein the synchronization module (25) further comprises an evaluation block (253) for evaluating the value of the at least one configuration bit (2521), and a switching block (254) for switching on or off the synchronization of the synchronization block (251) on the basis of the evaluation of the evaluation block (253). 10) Responder subscriber station (101; 102; ... 101 N) according to one of claims 7 to 9, wherein the responder subscriber station (101; 102; ... 101 N) is a subscriber station designed for communication according to CAN FD, wherein the predetermined frame (460) is a CAN FD frame in the FBFF format. 11) Responder subscriber station (101; 102; ... 101N) according to one of claims 7 to 10, wherein the predetermined bit rate is 2 Mbit / s. 12) Bus system (1), with a bus (40), and at least two subscriber stations (100; 101 ... 10N), 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 one subscriber station is a commander subscriber station (100) according to one of claims 1 to 5 and at least one subscriber station is a responder subscriber station (101 ... 101 N) according to one of claims 6 to 11, wherein each of the at least two subscriber stations (100; 101 ... 10N) additionally has a transmitting / receiving device (12; 22) for transmitting a transmit signal (TxD) to the bus (40) of the bus system (1) and / or for receiving a signal (VDIFF) from the bus (40) of the bus system (1). 13) Bus system (1) according to claim 12, further comprising at least one third subscriber station (100) which is designed to transmit and / or receive signals based on a frame (450; 460), wherein the at least one third subscriber station (100) has a communication control device (11) which is designed to negotiate with the commander subscriber station (100) in a first communication phase (451) of the frame (450; 460) whether the third subscriber station (100) or the commander subscriber station (100) in a subsequent second communication phase (452) is granted at least temporarily exclusive, collision-free access to the bus (40). 14) Method for communication in a serial bus system (1), wherein the method is carried out with a commander subscriber station (100) according to one of claims 1 to 5 and a responder subscriber station (101 ... 101 N) according to one of claims 6 to 11.

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