Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/407—Bus networks with decentralised control
  • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
  • H04L12/4135—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD] using bit-wise arbitration
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L43/00—Arrangements for monitoring or testing data switching networks
  • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
  • H04L43/0852—Delays
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L7/00—Arrangements for synchronising receiver with transmitter
  • H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
  • H04L7/0033—Correction by delay
  • H04L7/0041—Delay of data signal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L2012/40208—Bus networks characterized by the use of a particular bus standard
  • H04L2012/40215—Controller Area Network CAN

Definitions

• the present invention relates to a device and a measuring method for determining the internal delay time of a CAN bus connection unit or a CAN transceiver.
• CAN Controller Area Network
• the media access control method used in the CAN is based on bitwise arbitration. In CAN, the bitwise arbitration is performed on the basis of a leading identifier within the message to be transmitted over the bus.
• Subscriber stations may transmit a bit over the bus
• the transmission signal transmitted on the transmission channel is repeatedly compared with the reception signal. If at a certain point in time, the sample point, there is no match, the bus user terminates the transmission activity because it has to do so
• Bus subscribers who try to access the bus during arbitration. Because of the propagation times of the signals on the bus lines and because of intrinsic delay times in the bus connection units (transceivers), the result of the superimposition of these signals is late in the bit period, so that the sample point must be relatively far behind in the bit period. Among other things, this fact limits the permissible bit lengths at CAN down. Shortening is not possible without further ado.
• Delay time of a CAN bus connection unit or a CAN transceiver DELTA_T be measured by a specific method, which is described in DE 10 2012 200 997.
• a device and a measuring method for determining the internal delay time of a CAN bus connection unit which solve the aforementioned problems of the prior art.
• Determining the internal delay time of a CAN transceiver or a CAN bus connection unit are provided which generate no measurement errors in determining the internal delay time of a CAN transceiver or a CAN bus connection unit.
• a correct function of a serial data transmission in a bus system can be checked with at least two subscriber stations.
• each subscriber station is connected to the bus via a bus connection unit and can exchange messages via the bus, wherein the transmission access to the bus for each message by the
• the device comprises a unit for determining the internal
• the present invention describes a device incorporating a
• Delay time of a CAN transceiver or a CAN bus connection unit Delay time of a CAN transceiver or a CAN bus connection unit.
• a new configuration parameter is introduced, which determines in which time window faults on the CAN bus are hidden. This has the advantage that the value of the new parameter is set to an appropriate value based on an analysis of the CAN bus or network. This increases the robustness of the system.
• the minimum delay time may be a value dependent on the configuration value.
• the position of a SSP can be predetermined, in which a comparison of a transmission signal sent to the bus connection unit is carried out with a reception signal received from the bus connection unit.
• the device may include a delay unit for
• the apparatus may include a switching unit for switching between the instantaneous transmission signal and the transmission signal delayed by a predetermined time delay, so that the
• Comparison unit for checking the correct function of the data transmission either the instantaneous transmission signal or by the predetermined
• Time delay can use delayed transmission signal.
• the above object is also achieved by a measuring method for determining the internal delay time of a CAN bus connection unit with the
• a correct function of a serial data transmission in a bus system can be checked with at least two subscriber stations.
• each subscriber station is connected to the bus via a bus connection unit and can via the bus
• Delay counter for determining the delay time between a transmission signal and a reception signal, which delay counter is stopped when both the reception signal has a dominant level and the count of the delay counter is greater than / equal to a predetermined Configuration value, or determines the internal delay time based on the maximum and minimum delay time of the
• Bus interface unit The measuring method is carried out by the device described above and therefore offers the same advantages as the device.
• the minimum delay time may be a value dependent on the configuration value.
• the position of an SSP may possibly be specified, in which a comparison of a transmission signal transmitted by the bus connection unit with a received signal received from the bus connection unit is carried out.
• the measurement method can also generate a non-delayed
• Transmit signal and / or comparing a transmission signal sent to the bus terminal unit with a reception signal received from the bus terminal unit to check the correct function of the data transmission during the transmission, executed.
• either the undelayed one can be used to check the correct function of the data transmission
• Transmission signal can be used.
• FIG. 1 is a simplified block diagram of a bus system according to a first embodiment
• FIG. 2 is a timing diagram for illustrating the difference between the transmission signal and the reception signal on a CAN
• Fig. 3 is a schematic block diagram of a device according to the first embodiment.
• Fig. 1 shows a bus system 4, which may be, for example, a CAN bus system that can be used in a vehicle, in particular a motor vehicle, an aircraft, etc. or in the hospital.
• the bus system 4 has a device 5 and a multiplicity of subscriber stations 10, 20, 30 which are each connected to a bus 40 by means of a transceiver or a bus connection unit 11, 21, 31. Via the bus 40, data,
• the individual subscriber stations 10, 20, 30 are transmitted in accordance with the CAN specification in IS011898.
• the subscriber stations 10, 20, 30, which are also called nodes, can, for example, control devices or
• Fig. 2 shows the result of a laboratory examination
• a signal TXD denoted by 1 is the digital input signal or Transmission signal (CAN_TX) of a transceiver of one of the subscriber stations 10, 20, 30.
• a signal RXD denoted by 2 in FIG. 2 is the digital output signal or reception signal (CAN_RX) of a transceiver of one of the transceivers
• CAN_TX is the output of the protocol controller and the input of one of the bus connection units 11, 21, 31
• CAN_RX is the output of one of the bus connection units 11, 21, 31 and the input of the protocol controller.
• the transceiver also returns the TX signal on the RX signal, but with a delay. This delay is measured in the protocol controller according to the method described in more detail below
• the transmitter or transmitter of a single recessive bit which transmitter or transmitter is, for example, one of the subscriber stations 10, 20, 30, sees a short dip 3 dominant due to reflections within that bit.
• a single recessive bit with a break-in 3 is also referred to below as a faulty bit.
• the EDL bit at the end of which according to DE 10 2012 200 997 the delay time DELTA_T of a CAN transceiver is measured, is such a single recessive bit.
• Fig. 2 shows such disturbed bits.
• the low level or low level is dominant, the high level or high level is recessive.
• the signal RXD shows in FIG. 2 dips 3 after the rising edges. You can clearly see the delay time DELTA_T from the input signal or
• Transmission signal CAN_TX Since in DE 10 2012 200 997 the measurement is made from the falling edge of the transmission signal CAN_TX to the falling edge of the reception signal CAN_RX, in this case the measurement result would be zero.
• FIG. 3 shows a device 5 which can carry out a method according to the present exemplary embodiment.
• the device 5 may be of the respective
• Bus connection unit 11, 21, 31 includes or be provided in addition.
• the device 5 comprises a transmission shift register 300, a
• Delay counter 305 Delay counter 305, a delay unit 310, a comparison unit 320, a switching unit 330, an evaluation unit 340, as well as a
• Components can be combined or integrated.
• one bit of the serial data stream to be transmitted is output as a transmission signal CAN_TX via the corresponding connection line to the bus connection unit with each bit clock ,
• the received signal CAN_RX which via a
• Connection line is received by the bus connection unit or the transceiver is applied to the comparison unit 320 and the standard comparator 350.
• a start signal for the delay counter 305 is generated in the device 5.
• another configuration value is specified, a value T_MIN.
• the delay counter 305 is only stopped when both CAN_RX is dominant and the counter reading is greater than or equal to T_MIN.
• the delay counter 305 may then determine a time delay or delay time DELTA_T, for example, by counting oscillator cycles of an existing oscillator.
• T_MIN is, after measurements in the system development, chosen so that the collapse of the CAN_RX signal is safely completed when the count reaches T_MIN.
• the delay counter 305 generates a comparison point T_CMP as a function of the measured delay time DELTA_T.
• this comparison point T_CMP can be generated as the sum of the determined delay time DELTA_T and a predefined or specifiable percentage of the bit length, in particular of half the bit length.
• the comparison point T_CMP defines the point in time at which the XOR connection between the delayed transmission signal CAN_TX_DEL and the reception signal CAN_RX in the comparison unit 320 is evaluated.
• the delay unit 310 generates or generates from the transmission signal CAN_TX and its transmitted from the delay counter 305
• the comparison unit 320 receives the received signal CAN_RX and the delayed transmission signal CAN_TX_DEL. Furthermore, the comparison unit 320 receives from the delay counter 305 information T_CMP about a suitable comparison point to which the comparison result between the received signal CAN_RX and the delayed transmission signal CAN_TX_DEL is to be sampled. The comparison unit 320 thus generates an output signal which reproduces the result of the comparison and is forwarded to the switching unit 330, for example a multiplexer.
• the standard comparator 350 which may be designed, for example, as an XOR gate, generates a second output signal, which reproduces the result of the comparison between CAN_TX and CAN_RX and is also forwarded to the switching unit 330.
• the switching unit 330 switches over between the two signals, for example by means of a suitable signal SWT and / or based on stipulated specifications, which may include, for example, reaching or evaluating a predetermined or specifiable bit, so that either the output signal of the Norm conveyers 350 or the comparison unit 320 is applied to the evaluation unit 340.
• the switching unit 330 switches over to the BRS bit of a CAN signal, provided there is a switch to shorter bit lengths.
• the evaluation unit 340 is then at the configured sample point T_SMP each by the
• Switching unit 330 through-sampled signal and optionally generates a bit error signal BERR, if no match was detected.
• a measuring method and a check of the correct function of a serial data transmission in a bus system 4 with at least two bus users for example the
• the bus users or the subscriber stations 10, 20, 30 are connected to the bus 40 via a transceiver or a bus connection unit 11, 21, 31 and can exchange messages 41 via the bus 40, wherein the transmission access to the bus 40 for each message 41 by the Arbitration method according to CAN standard ISO 11898-1 to a bus subscriber, the subscriber stations 10, 20, 30, is awarded, which is for this message 41 to the transmitter.
• the messages 41 have a logical structure in accordance with the CAN standard, ie are composed of start-of-frame bits, arbitration fields, control fields, data fields, CRC fields, acknowledge fields and end-of-frame fields. In this case, a comparison of a transmission signal transmitted to the bus connection unit 11, 21, 31 with the CAN_TX received by the bus connection unit 11, 21, 31
• Received signal CAN_RX the correct function of the data transmission during transmission checked, wherein in the transmitter with respect to the transmission signal CAN_TX delayed by a delay DELTA_T transmission signal
• CAN_TX_DEL is maintained, and depending on a switch for the check of the correct function of the data transmission, the undelayed transmission signal CAN_TX or delayed by the time delay T_DELAY transmission signal CAN_TX_D EL is used.
• a configuration value T_M IN is specified, so that a value dependent on the configuration value T_M IN is used as the minimum value of the delay time DELTA_T.
• Delay time DELTA_T completely omitted. Instead, the position of the second Sample Point (Secondary Sample Point) SSPs is fixed. To specify a fixed position, one must know both the maximum and the minimum internal delay time DELTA_T of a CAN transceiver, and these two values must not be too far apart. So far, there is only an indication of the maximum in the data sheets of the transceiver. Therefore, in this case, the minimum is specified in the data sheet.
• the measurement can be dispensed with and then a delay time DELTA_T
• Bus connection unit 11, 21, 31 known minimum and maximum
• Subscriber station 10, 20, 30 can be used in particular for CAN FD (CAN with Fl data rate) and for TTCAN FD (TTCAN with Flexible Data rate) networks.
• CAN FD CAN with Fl data rate
• TTCAN FD TTCAN with Flexible Data rate
• Bus system 4 of the embodiments is arbitrary.
• Measurement method can also be applied to a modified data protocol, which on 02.05.2011 on the Internet site

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• 2013
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