TRANSMIT / RECEIVE DEVICE FOR A BUS SYSTEM AND OPERATING PROCEDURES FOR IT

Description

State of the art

[0001] The invention relates to a transmitter / receiver device for a bus system, wherein the transmitter / receiver device has a first bus connection for connection to a first signal line of the bus system, a second bus connection for connection to a second signal line of the bus system and a receiver unit for receiving a bus reception signal from the first and second bus connections.

[0002] The invention further relates to a method for operating such a transmitting / receiving device.

[0003] German patent DE 102015222334A1 discloses a device and a method for selectively suppressing bus oscillations during data reception via a bus system. The known device includes a masking element for masking oscillations of the bus signal. The masking element is comparatively complex. US patent 2011 / 285424 A1 describes a differential communication device. Disclosure of the invention

[0004] It is therefore an object of the present invention to improve a transmitting / receiving device of the type mentioned above and an operating method for it in such a way as to reduce or avoid the aforementioned disadvantages of the prior art.

[0005] A transmit / receive device for a bus system according to claim 1 is proposed. This advantageously enables a reduction of unwanted bus oscillations without the need for a comparatively complex masking unit, as known from the prior art. By connecting the bus terminals using a predefinable electrical resistance for a predefinable initial period, any bus oscillations that may occur can be advantageously reduced because greater damping results from the added resistance during this initial period. Furthermore, it is advantageous that the initial period can be flexibly defined, allowing the resistance to be activated for an optimal duration, for example, until sufficient damping of unwanted bus oscillations has occurred, but no longer.

[0006] The receiving unit includes a receiving comparator configured to generate a bus differential signal as a function of the bus received signal, wherein at least one operating parameter of the receiving unit is the bus differential signal or a signal derived therefrom. This allows the predefined first time duration to be determined with particular precision.

[0007] The receiving comparator has several receiving thresholds, especially for the bus differential signal, which makes it particularly efficient to determine how long the resistance should be connected to the bus lines (predefinable first time duration).

[0008] A first reception threshold is at approximately 0.7 volts, a second reception threshold is at a value less than approximately 0 volts, and, in particular, a third reception threshold lies between approximately 0 volts and the first reception threshold. According to investigations by the applicant, this makes it particularly easy and precise to determine the first time duration.

[0009] The transmit / receive device is configured to connect the first and second bus terminals via the predefinable electrical resistance for the predefinable first duration when at least one of the following conditions is met: a) a rising edge of a transmit input signal for a transmit unit of the transmit / receive device, b) a state transition of the transmit unit from an operating state that drives the first and second bus terminals to an operating state that does not drive the first and second bus terminals, c) a falling edge of a differential signal derived from the bus receive signal by means of the receiving unit.

[0010] In further embodiments, the predefinable electrical resistance has a value between about 40 ohms and about 200 ohms, preferably between about 80 ohms and about 160 ohms, more preferably between 100 ohms and about 140 ohms, and most preferably about 120 ohms.

[0011] Further aspects of the embodiments are specified by a subscriber station for a bus system with at least one transmitting / receiving device according to the embodiments.

[0012] Further aspects of the embodiments are specified by a bus system with a bus line having at least one first signal line and at least one second signal line, and with at least two subscriber stations, wherein at least one of the at least two subscriber stations has at least one transmitting / receiving device according to the embodiments.

[0013] Further aspects of the embodiments are specified by a method for operating a transmitting / receiving device for a bus system according to claim 7. Advantageous further developments are the subject of the dependent claims.

[0014] Further features, applications, and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are illustrated in the figures. All described or illustrated features, individually or in any combination, constitute the subject matter of the invention, irrespective of their inclusion in the claims or their cross-reference, and irrespective of their formulation or representation in the description or in the drawing.

[0015] The drawing shows: Figure 1 schematically shows a simplified block diagram of a bus system according to one embodiment, Figure 2 schematically shows a simplified block diagram of a bus system according to another embodiment, Figure 3 schematically shows a block diagram of a transmit / receive device according to one embodiment, Figure 4 schematically shows a block diagram of a resistor device according to one embodiment, Figure 5 schematically shows a block diagram of a transmit / receive device according to another embodiment, Figure 6 a simplified flow diagram of a method according to one embodiment, and Figure 7 schematically shows a time course of an operating parameter according to one embodiment.

[0016] Figure 1 Figure 1 schematically shows a simplified block diagram of a bus system 1 according to an embodiment, which can be used in a vehicle, in particular a motor vehicle, an aircraft, etc., or in an industrial robot, etc. Fig. 1The bus system 1 has a first participant station 110, a second participant station 120, a third participant station 130, a fourth participant station 140, a fifth participant station 150, a bus line 160, and a terminating resistor 170, wherein the participant stations 110 to 150 are arranged in a star topology. The bus system 1 can be, for example, a CAN bus system or a CAN FD bus system, etc. In general, in the present embodiment, the bus system 1 is configured for communication in which at least temporarily exclusive, collision-free access of one of the participant stations 110 to 150 to the bus line 160 is guaranteed. The first participant station 110 can, for example, be a control unit of a motor vehicle. The second, fourth, and fifth participant stations 120, 140, and 150 can, for example, each be a sensor of the motor vehicle.The third participant station 130 could, for example, be a display device of a motor vehicle.

[0017] Figure 2 Figure 1 shows a bus system 2 according to a further embodiment. In contrast to bus system 1 according to the first embodiment, bus system 2 according to the second embodiment has a linear bus topology with two terminating resistors 170a, 170b at respective ends of the bus line 160. The subscriber stations 110 to 150 can be connected to bus system 2 according to the second embodiment. Fig. 2 be structured in the same way as with Fig. 1 .

[0018] Figure 3 Figure 1 shows a schematic block diagram of a transmit / receive device 10 for a bus system according to one embodiment. For example, the following can be illustrated with reference to Figure 3 described transmitting / receiving equipment 10 in at least one subscriber station 110, .., 150 of the above with reference to the Figure 1, 2The described bus systems 1 and 2 are used.

[0019] The transmit / receive device 10 has a first bus connection 12a for connection to a first signal line 1a of the in Fig. 3 a schematically indicated bus system 1, and a second bus connection 12b for connection to a second signal line 1b of bus system 1. For example, bus line 160 ( Fig. 1 ) so the two signal lines 1a, 1b.

[0020] The transmit / receive device 10 also includes a receiver unit 18 for receiving a bus receive signal BE from the first and second bus terminals 12a, 12b. For this purpose, the receiver unit 18 is connected to the bus terminals 12a, 12b via its terminals 18a, 18b.

[0021] According to the invention, the transmitting / receiving device 10 is designed to connect the first and second bus connections 12a, 12b to each other for a predefinable first period of time via a predefinable electrical resistance.

[0022] This can be done, for example, via the in Fig. 3 The exemplary resistor device 17 shown is connected via its terminals 17a, 17b to the bus terminals 12a, 12b, and which, for example, connects the in Figure 4 The structure shown is as depicted.

[0023] The resistance device 17 can have an electrical resistance R with a value between about 40 ohms and about 200 ohms, preferably between about 80 ohms and about 160 ohms, more preferably between 100 ohms and about 140 ohms, and most preferably with about 120 ohms, as well as a switch 17c arranged in series with it, which is provided by a control signal a1, in this case for example by the receiving unit 18 ( Fig. 3), is controllable. In other embodiments, the resistance device 17 can, for example, also comprise a semiconductor component, in particular a field-effect transistor or the like, whose drain-source path can be controlled under the influence of the control signal a1, for example, between a high-impedance state ("no damping resistor switched on") and an operating state with a resistance of the drain-source path in the aforementioned range, for example of about 120 ohms.

[0024] According to the invention, the first predefinable time period for which the resistor R can be activated with respect to the bus connections 12a, 12b is selectable depending on at least one operating parameter of the receiving unit 18. This ensures that the resistor R can be activated for as long as is useful for the operation of the receiving unit 18 or the device 10, but, for example, not longer. For instance, the receiving unit 18 specifies the first predefinable time period for which the resistor R is activated with respect to the bus connections 12a, 12b, which is done, for example, via the control signal a1.

[0025] Optionally, the transmit / receive device 10 can also have a transmitter unit 14 for outputting a bus termination signal to the first and second bus terminals 12a, 12b, for example, to send information via bus line 160 to other subscriber stations or their respective transmit / receive devices (not shown). Preferably, the transmitter unit 14 is connected to the bus terminals 12a, 12b via its terminals 14a, 14b.

[0026] Figure 5 Figure 1 schematically shows a block diagram of a transmit / receive device 10a according to a further embodiment, which in this case is configured, for example, for operation on a bus system 1 designed as a CAN FD bus system. Below, only the differences to configuration 10 according to Figure 1 are described. Fig. 3As described. The transmitter / receiver 10a is connected via terminal 11a to a first reference potential CAN_GND, which is, for example, a ground potential. The transmitter / receiver 10a is connected via terminal 11b to a second reference potential CAN_SUPPLY, which is, for example, a reference potential corresponding to an operating voltage of, for example, +5 volts.

[0027] The transmitter unit 14 has a transmit signal driver 141 which, depending on a transmit input signal TxD supplied to it, generates an output signal for controlling the two semiconductor switches 142a, 142b. As can be seen from Figure 5As can be seen, when the first semiconductor switch 142a is appropriately controlled by the transmit input signal TxD (or the amplified transmit input signal TxD'), the first terminal 14a of the transmitter unit 14, via which the transmitter unit 14 is connected to the first bus terminal 12a, can be set to an electrical potential dependent on the second reference potential CAN_SUPPLY. Similarly, when the first semiconductor switch 142b is appropriately controlled by the transmit input signal TxD, the second terminal 14b of the transmitter unit 14, via which the transmitter unit 14 is connected to the second bus terminal 12b, can be set to an electrical potential dependent on the first reference potential CAN_GND. This operating state of the transmitter unit 14 is therefore also referred to as the driving operating state of the transmitter unit 14. A non-driving operating state of the transmitter unit 14 results accordingly when the relevant connections 14a, 14b or 14b are closed.12a, 12b are not connected to the aforementioned potentials by the semiconductor switches 142a, 142b. This state can also be described as the high-impedance state of the transmitter unit 14. Undesired bus oscillations can occur, for example, when the transmitter unit 14 switches from the driving operating state to the non-driving operating state. In such cases, the bus oscillations can advantageously be damped by means of the resistor device 17, applying the principle described above.

[0028] Even at the in Figure 5 According to the exemplary configuration described, the procedure can therefore be carried out according to the embodiments, cf. the resistance device 17 and the control signal a1. Figure 6 Figure 1 shows a simplified flowchart of a method according to one embodiment. In step 200, the transmit / receive device 10a selects ( Fig. 5) the predefinable first time duration depending on at least one operating parameter of the receiving unit 18, and in step 210 the transmitting / receiving device 10a connects the bus connections 12a, 12b via the resistor R ( Fig. 4 ) the resistance device 17 for this previously selected first time period together.

[0029] In other embodiments, an at least partially overlapping execution of steps 200 and 210 is also conceivable. For example, a start time for the activation of the resistance device 17 can first be selected and the device activated accordingly, and then, depending on at least one operating parameter of the receiving unit 18, the predefinable time duration for the activation of the resistance device 17 can be determined, and the activation can be terminated after this time has elapsed.

[0030] In further preferred embodiments, the receiving unit 18 ( Fig. 5A receiver comparator 181 is configured to generate a bus differential signal VDIFF as a function of the bus received signal, wherein at least one operating parameter of the receiver unit 18 is the bus differential signal VDIFF or a signal derived therefrom. This allows the predefined first time duration to be determined with particular precision. For example, the bus differential signal VDIFF can be generated from the bus signals CAN_H and CAN_L using a differential amplifier 182. The bus differential signal VDIFF can also be viewed as an analog differential voltage between the CAN bus lines CAN_H and CAN_L. Here, VDIFF = CAN_H - CAN_L. The differential voltage VDIFF is, for example, 0V for a recessive bit and typically 2V for a dominant bit.

[0031] In further embodiments, the receiving comparator 181 has several receiving thresholds TH1, TH2, ... , in particular for the bus differential signal VDIFF, which makes it particularly efficient to determine for how long the resistance R ( Fig. 4 ) to be connected to bus lines 12a and 12b. Control is achieved via the control signal a1, which is used during the configuration of the Figure 5 can be formed by the receiving comparator 181 and output to the resistor device 17.

[0032] In further embodiments, a first reception threshold TH1 is at approximately 0.7 volts, wherein in particular a second reception threshold TH2 is at a value less than approximately 0 volts, and wherein in particular a third reception threshold TH3 is between approximately 0 volts and the first reception threshold. According to investigations by the applicant, this makes it particularly easy and precise to determine the first time duration.

[0033] Figure 7Figure 1 schematically shows a time course of the bus differential signal VDIFF according to one embodiment. At time t1, i.e., in this case at the falling edge of the bus differential signal VDIFF, undesired oscillations begin, which are suppressed by switching on the resistor R ( Fig. 4 ) can be dampened for the predefinable first time period T1, i.e. until time t2.

[0034] In other embodiments, the transmitting / receiving device 10a ( Fig. 5) designed to connect the first and second bus terminals 12a, 12b to each other via the predefinable electrical resistance R for the predefinable first time period when at least one of the following conditions is met: a) a rising edge of a transmit input signal TxD for the transmit unit 14 of the transmit / receive device 10a, b) a state transition of the transmit unit 14 from an operating state driving the first and second bus terminals to an operating state not driving the first and second bus terminals, c) a falling edge of a differential signal VDIFF derived from the bus receive signal BE by means of the receive unit 18 ( Fig. 7 ). The start time t1 for the activation of the resistor R can therefore be selected depending on at least one of these criteria.

[0035] In contrast, the predefinable first time duration T1 is advantageous depending on at least one operating parameter of the receiving unit 18 ( Fig. 5) selectable, in this case for example depending on the time course VDIFF, e.g. in relation to falling below and / or exceeding at least one of the mentioned reception thresholds TH1, TH2, TH3.

[0036] In some embodiments, it may be provided that the differential signal VDIFF ( Fig. 7) is monitored for falling below the negative receive threshold TH2, and then whether the first receive threshold TH1 is exceeded or not exceeded after a detected (one or more) falling below the negative receive threshold TH2 within a predefinable waiting time, which is preferably less than one bit time of the data transmission on the bus system (in particular significantly less, e.g. less than about 20 percent of the bit time of the data transmission on the bus system). For example, ifThe negative reception threshold TH2 has been undercut by the differential signal VDIFF, and provided that, within the specified waiting period after this undercutting of the negative reception threshold TH2, the first reception threshold TH1 has not been exceeded by the differential signal VDIFF, it can be concluded that although an undesirable oscillation of the differential signal VDIFF was present (due to the undercutting of the negative reception threshold TH2), this undesirable oscillation has since (within the waiting period) sufficiently subsided (due to the first reception threshold TH1 not being exceeded within the waiting period). This state is in . Fig. 7approximately at time t2. Between times t1 and t2, in the present example, the negative reception threshold TH2 is undercut a total of three times, and the first reception threshold TH1 is exceeded after the first and second instances of undercutting the negative reception threshold TH2. However, after the third instance of undercutting the negative reception threshold TH2, the first reception threshold TH1 is only just reached, if at all, but is no longer exceeded (see time t2). Therefore, in some embodiments, the connection of the resistor R ( Fig. 4 ) be deactivated. In further embodiments, it may also be provided that the resistance R is deactivated from time t2 plus a predefinable protection time of, for example, approximately 5 nanoseconds to approximately 10 nanoseconds, whereby the unwanted oscillation is then particularly reliably reduced to a tolerable level.

[0037] In other words, in some embodiments, the transmit / receive device 10, 10a can be configured to monitor the differential signal VDIFF for falling below the negative receive threshold TH2, and to check whether the first receive threshold TH1 is exceeded after a detected (in particular, one or more instances) falling below the negative receive threshold TH2 within a predefinable waiting period, which is preferably shorter (in particular, significantly shorter) than a bit time of the data transmission on the bus system. The time at which these conditions are met can be used as the end of the predefinable first time period T1, i.e., as a signal to deactivate the resistor R.

[0038] In preferred embodiments, the predefinable first time duration T1 ( Fig. 7 ) for the activation of the resistor R ( Fig. 4The duration is typically selectable between approximately 40 ns (nanoseconds) and approximately 150 ns. Other values ​​are also conceivable in further embodiments.

[0039] The principle according to the embodiments is not limited to application in CAN or CAN-FD bus systems, but can also be used, for example, in LVDS or LIN bus systems or generally in all bus systems with dominant and recessive bus states.

Claims

1. Transmission / reception device (10; 10a) for a bus system (1; 2), wherein the transmission / reception device (10; 10a) has a first bus connection (12a) for connecting to a first signal line (1a; CAN_H) of the bus system (1; 2), a second bus connection (12b) for connecting to a second signal line (1b; CAN_L) of the bus system (1; 2), and a reception unit (18) for receiving a bus reception signal (BE) from the first and second bus connections (12a, 12b), wherein the transmission / reception device (10; 10a) is designed to connect (210) the first and second bus connections (12a, 12b) to each other via a predefinable electrical resistance (R) for a predefinable first period of time (T1), wherein the predefinable first period of time (T1) is able to be selected in dependence on at least one operating variable of the reception unit (18), wherein the reception unit (18) has a reception comparator (181) which is designed to form a bus differential signal (VDIFF) in dependence on the bus reception signal (BE), wherein the at least one operating variable of the reception unit (18) is the bus differential signal (VDIFF) or a signal derived therefrom, wherein the transmission / reception device (10; 10a) is designed to connect the first and second bus connections (12a, 12b) to each other via the predefinable electrical resistance (R) for the predefinable first period of time if at least one of the present conditions is present: a) a rising edge of a transmission input signal (TxD) which is able to be supplied to a transmission unit (14) of the transmission / reception device (10; 10a), b) a state transition of the transmission unit (14) from an operating state driving the first and second bus connections (12a, 12b) to an operating state not driving the first and second bus connections (12a, 12b), c) a falling edge of a differential signal (VDIFF) derived from the bus reception signal (BE) by means of the reception unit (18), wherein the reception comparator (181) has a plurality of reception thresholds (TH1, TH2, TH3), in particular for the bus differential signal (VDIFF), wherein a first reception threshold (TH1) is at about 0.7 volts, wherein a second reception threshold (TH2) is at a value of less than about 0 volts, wherein the transmission / reception device (10; 10a) is designed to monitor whether the differential signal (VDIFF) falls below the second reception threshold (TH2), and then, after said differential signal has been detected to fall below the second reception threshold (TH2), for example one or more times, within a predefinable wait time, which is less than a bit time of a data transmission on the bus system (1; 2), whether or not the first reception threshold (TH1) is exceeded, wherein the transmission / reception device (10; 10a) is designed to use a time (t2), at which the first reception threshold (TH1) is no longer exceeded after said differential signal has been detected to fall below the second reception threshold (TH2), as the end of the predefinable first period of time (T1).

2. Transmission / reception device (10; 10a) according to Claim 1, wherein the predefinable wait time is less than about 20 per cent of the bit time of the data transmission on the bus system (1; 2).

3. Transmission / reception device (10; 10a) according to at least one of the preceding claims, wherein a third reception threshold (TH3) is between about 0 volts and the first reception threshold (TH1).

4. Transmission / reception device (10; 10a) according to at least one of the preceding claims, wherein the predefinable electrical resistance (R) has a value of between about 40 ohms and about 200 ohms, preferably of between about 80 ohms and about 160 ohms, more preferably of between 100 ohms and about 140 ohms, most preferably of about 120 ohms.

5. Subscriber station (110, 120, 130, 140, 150) for a bus system (1; 2) having at least one transmission / reception device (10; 10a) according to at least one of the preceding claims.

6. Bus system (1; 2) having a bus line (160) which has at least a first signal line (1a; CAN_H) and at least a second signal line (1b; CAN_L), and having at least two subscriber stations (110, 120, 130, 140, 150), wherein at least one of the at least two subscriber stations (110, 120, 130, 140, 150) has at least one transmission / reception device (10; 10a) according to at least one of Claims 1 to 4.

7. Method for operating a transmission / reception device (10; 10a) for a bus system (1; 2), wherein the transmission / reception device (10; 10a) has a first bus connection (12a) for connecting to a first signal line (1a; CAN_H) of the bus system (1; 2), a second bus connection (12b) for connecting to a second signal line (1b; CAN_L) of the bus system (1; 2), and a reception unit (18) for receiving a bus reception signal (BE) from the first and second bus connections (12a, 12b), wherein the transmission / reception device (10; 10a) is designed to connect (210) the first and second bus connections (12a, 12b) to each other via a predefinable electrical resistance (R) for a predefinable first period of time, wherein the transmission / reception device (10; 10a) selects (200) the predefinable first period of time in dependence on at least one operating variable of the reception unit (18), wherein the reception unit (18) has a reception comparator (181) which is designed to form a bus differential signal (VDIFF) in dependence on the bus reception signal (BE), wherein the at least one operating variable of the reception unit (18) is the bus differential signal (VDIFF) or a signal derived therefrom, wherein the transmission / reception device (10; 10a) connects the first and second bus connections (12a, 12b) to each other via the predefinable electrical resistance (R) for the predefinable first period of time if at least one of the present conditions is present: a) a rising edge of a transmission input signal (TxD) which is able to be supplied to a transmission unit (14) of the transmission / reception device (10; 10a), b) a state transition of the transmission unit (14) from an operating state driving the first and second bus connections (12a, 12b) to an operating state not driving the first and second bus connections (12a, 12b), c) a falling edge of a differential signal (VDIFF) derived from the bus reception signal (BE) by means of the reception unit (18), wherein the reception comparator (181) has a plurality of reception thresholds (TH1, TH2, TH3), in particular for the bus differential signal (VDIFF), wherein a first reception threshold (TH1) is at about 0.7 volts, wherein a second reception threshold (TH2) is at a value of less than about 0 volts, wherein the transmission / reception device (10; 10a) monitors whether the differential signal (VDIFF) falls below the second reception threshold (TH2), and then, after said differential signal has been detected to fall below the second reception threshold (TH2), for example one or more times, within a predefinable wait time, which is less than a bit time of a data transmission on the bus system (1; 2), whether or not the first reception threshold (TH1) is exceeded, wherein the transmission / reception device (10; 10a) uses a time (t2), at which the first reception threshold (TH1) is no longer exceeded after said differential signal has been detected to fall below the second reception threshold (TH2), as the end of the predefinable first period of time (T1).

8. Method according to Claim 7, wherein the predefinable wait time is less than about 20 per cent of the bit time of the data transmission on the bus system (1; 2).