Abstract:
Transmission and/or reception circuit arrangement for the physical implementation of a motor vehicle data bus system and use thereof, wherein the circuit has a plurality of configurable modes of operation which are a different physical implementation of one or more logic states and also comprises electronic bit generation and/or bit reception circuit elements which are used in each mode of operation, wherein changeover and/or structure elements are present which can be used to change over the circuit arrangement between the modes of operation and/or to operate said circuit arrangement in different modes of operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2008/050379, filed Jan. 15, 2008, which claims priority to German Patent Application No. DE 102007003326.7, filed Jan. 17, 2007 and German Patent Application No. DE 102008004551.9, filed Jan. 15, 2008,the contents of such applications being incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a transmission and/or reception circuit arrangement for the physical implementation of a motor vehicle data bus system and the use thereof in a motor vehicle controller. 
         [0004]    2. Description of the Related Art 
         [0005]    FlexRay(R) is a bus standard for electronic controllers in motor vehicles which is intended to allow particularly rapid, realtime-compatible and error-tolerant transmission of the data. FlexRay(R) is regarded by many leading motor vehicle manufacturers and their suppliers as the future standard which, at least in subdomains, is meant to replace the CanBus(R) data transmission technology used in practically all motor vehicles. 
         [0006]    The CanBus(R) technology, or the network formed thereby, is used for the data interchange between the electronic controllers, sensors and actuators which are increasingly present in the vehicle. FlexRay(R) allows improved and faster data transmission in comparison with CAN essentially through the use of fixed time windows and error-tolerant and redundant transmission on two channels. 
         [0007]    An electronic FlexRay(R) driver circuit (physical layer) based on the prior art essentially comprises two high-side and two low-side driver stages which can produce two different dominant, that is to say actively driven, states (inverted difference voltage) on the bus. Depending on the state “0” or “1”, a high-side driver and a low-side driver are respectively connected in series; the electrical connection between the drivers is formed by the connections on the bus lines BP and BM. 
         [0008]    By contrast, a CAN driver is known to comprise just a high-side driver stage and a low-side driver stage, since only a dominant (actively driven) state needs to be produced. The output of the high-side driver is connected to the CAN-H bus line, and the output of the low-side driver is connected to the CAN-L bus line. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the present invention is now to specify a transmission and/or reception circuit for the physical implementation of a motor vehicle data bus which is flexibly configurable and of simple design. 
         [0010]    In at least one aspect, the invention addresses the following problem: in order to be universally usable, controllers must frequently provide both a CAN bus connection and a FlexRay(R) connection. An inherently known FlexRay transceiver is usually larger and therefore more expensive than a CAN transceiver. The invention contains the idea that partially combining circuit elements from the two conventional CAN transceivers provides the opportunity to use the transceiver formed for a plurality of bus types, that is to say particularly CAN and FlexRay. Furthermore, one exemplary embodiment makes it possible to change between a FlexRay connection and two CAN connections. 
         [0011]    In at least one aspect, the invention relates to a transmission circuit arrangement and/or a reception circuit arrangement for the physical implementation of a motor vehicle data bus system. Said circuit arrangement comprises terminals for the connection of a bus line which can be used to transmit bus data. The terminals are preferably connected to a CanBus or to a FlexRay bus. Furthermore, the circuit arrangement comprises output terminals to which, by way of example, a digital processing unit is connected which, by way of example, may be a microcontroller for processing the bus data. Logic levels are applied to the output terminals on the basis of the bus data which are to be sent or received. The circuit arrangement has, in particular, one or more control lines which can be used to configure the behavior of the circuit arrangement. 
         [0012]    In addition, the circuit has a plurality of modes of operation with different physical implementations of one or more logic states (for example “0” or “1”). In this case, physical implementation is understood to mean the conversion of the binary states into electrical signals. 
         [0013]    In addition, the circuit contains electronic bit generation and/or bit reception circuit elements which are used in each mode of operation. These common circuit elements, which are drivers and/or comparators, for example, can be used either in a first mode of operation or for a further, particularly second mode of operation. 
         [0014]    Finally, the inventive circuit arrangement also contains changeover and/or structure means. By way of example, the changeover means can be used for mode changeover and/or configuration on the basis of the signals on the control line(s). To this end, the control lines are preferably connected to at least one appropriate control module. As explained further above, mode changeover and/or configuration can also be effected using structure means. Structure means refer to different external interconnections for the inputs and/or outputs of the circuit or else to wire bridges or the like, which can be subsequently soldered to the circuit by the user of the circuit, for example. Another example of a structure means is a control input or a bus input (for example SPI bus) of the circuit, which input can be used to change over the circuit to different modes of operation. To this end, particularly a memory (for example FlipFlop, EEPROM) is present on the circuit and stores the last programmed operating state. 
         [0015]    The invention preferably defines a universal transceiver which, depending on the mode of operation, allows FlexRay(R) and/or CanBus(R) data communication. 
         [0016]    In a controller which already has two or more CAN connections (and appropriate electronic transceiver elements therefore), it may be advantageous to provide a FlexRay connection instead of a CAN connection (or else both CAN connections). Since the transceiver electronics which belong to this FlexRay connection can also be operated as a CanBus, as shown above, this uses up less chip area, particularly when implemented on an integrated chip. This results in significant cost advantages for production in large quantities. The inventive driver or reception circuit is therefore particularly suitable for use as part of a user-specific circuit (ASIC), which is preferred, since normally these are produced in large quantities, which means that component savings are advantageous for economic reasons. An additional effect advantageously achieved is that pin compatibility between CAN mode and FlexRay(R) mode exists for the bus connections and the logic inputs and outputs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Further advantages and features of the invention will be apparent from the following description of an exemplary embodiment with reference to figures, in which 
           [0018]      FIG. 1  shows a block diagram with a driver node for operation in a FlexRay(R) network, 
           [0019]      FIG. 2  shows a plurality of connection examples for terminals of a function block on a CAN or FlexRay(R) bus, 
           [0020]      FIG. 3  shows a driver module with a function block as shown in  FIG. 2 , 
           [0021]      FIG. 4  shows a receiver module with two modes of operation (CAN and FlexRay(R)), 
           [0022]      FIG. 5  shows a further example of a receiver module which, like the receiver module in  FIG. 4 , can be used both for FlexRay(R) and for CAN and 
           [0023]      FIG. 6  shows a conventional, commercially available FlexRay(R) standard chip (FlexRay(R) transceiver) which, by means of special actuation/interconnection, is used as a CAN chip. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    In  FIG. 1 , the drivers  1  . . .  4  (HS 1 , HS 2 , LS 1 , LS 2 ) form a network node which is connected by means of terminals  5  and  6  to data bus  7 . Bus  7  comprises the bus lines  8  (BP) and  9  (BM) of a FlexRay(R) network. Bus  7  has further bus subscribers, e.g. receiver nodes—not shown—or a bus termination  10 , connected to it. Control lines  11  can be used by control electronics—not shown—to actuate the drivers  1  . . .  4 . Suitable actuation of the drivers  1  . . .  4  allows a defined flow of current from node  5  to node  6  (or in the opposite direction) to be set. On the basis of the FlexRay(R) specification, the current direction determines the binary state “1” or “0” for a data bit which is to be transmitted via the bus. In the “1” state, a current flows from high-side driver  1  via line  8  to termination  10  (or to the receiver). From there, the current flows back via line  9  to low-side driver  4 . When the “0” state is transmitted, the current flows from high-side driver  2  via line  9  to termination  9  and from there back via line  8  to low-side driver  3 . Besides these two binary states, the FlexRay(R) specification is also known to comprise what is known as an “IDLE” state, which is obtained when the signal edges change between the binary states. 
         [0025]      FIG. 2   a  shows the driver node as function block  12  (chip or module) generally with four bus connection terminals  13  . . .  16 . Image section b) shows the interconnection of the terminals  13  . . .  16  of the function block  12  when used as a FlexRay(R) driver. Image section c) shows the interconnection of the terminals  13  . . .  16  of the function block  12  when used as a CAN driver, with two CAN drivers advantageously being able to be implemented for bus “CAN1” and “CAN2”. 
         [0026]    The aforementioned drivers are respectively compiled from two individual high-side driver stages  1 ,  2  and two low-side driver stages  3 ,  4 , for which the connections  13  . . .  16  of all four stages are routed out individually. External interconnection now makes it possible to present either a FlexRay driver by shorting pins  13  and  16  and pins  14  and  15 , with the bus termination being situated between lines  8  and  9 , or two CAN drivers by interconnecting the termination for bus “CAN1” between pins  14  and  15  and a termination for bus “CAN2” between pins  13  and  16 . As an alternative to the option of stipulating the mode of operation by means of external interconnection, there is likewise preferably the option of automatically associating the external connections  13  to  16  using a coupling module, in which case the coupling module is particularly part of the circuit arrangement according to the invention. 
         [0027]    The driver module  12  in  FIG. 3  comprises not only the driver stages shown in  FIG. 2  but additionally a driver control block  20  which can be used to produce control signals  11  for the driver stages  1  . . .  4 . On the side which faces the microcontroller—not shown—(the receiver is considered separately further below), module  12  has two input connections  17  and  18  which can be configured differently using control line  19 . The lines  17  to  19  are connected to control block  20 . Line  19  can be used to select two modes of operation for the control block  20 . In “CAN” mode, line  17  has the functionality of the connection “TX” of a conventional CAN driver for the first CanBus “CAN1” (see  FIG. 2 ). In this mode, line  18  is associated with the connection “TX” for the second CanBus “CAN2” (see  FIG. 2 ). In the “FlexRay” mode of operation, line  17  is connected to the functionality of the standardized FlexRay(R) connection “FR”. Line  18  is then connected to the likewise standardized connection “FR-TXEN”. Control signal  19  for setting the modes can be provided by means of an SPI bus, for example, with a memory bit being set in the controlled block according to the mode of operation. 
         [0028]      FIG. 4  shows a universally usable receiver module  21  which can be programmed in a similar manner to the driver (transmitter) in  FIG. 3  by a receiver control block  20 ′ such that two modes of operation are available. Receiver  21  comprises a plurality of comparators  22 ,  25  and  25 ′ which form respective logic signals from difference voltages (e.g. voltage U on terminals  13  and  14 ). In the “FlexRay(R)” mode of operation shown, terminals  13  and  16  and also  14  and  15  are shorted (bridges  35  and  36 ). The difference voltages are then obtained from the levels which are on the bus lines  8  (BP) and  9  (BM). In the region of the comparators  22 ,  25  and  25 ′, the difference signal can also be compared with a reference voltage. If the difference voltage is above an upper switching threshold for the comparator  22 , receiver  21  outputs a “dominant 1” signal, with simultaneous RxEN=0. If the difference voltage is below a lower switching threshold, the receiver outputs a “dominant 0” signal, with simultaneous RxEN=0.The outputs are made via lines  23  and  24 . 
         [0029]    Viewed in simple terms, a CAN receiver module essentially comprises a comparator (see also comparator  25 ) which is supplied with the difference voltage applied to terminals  14  (CAN 1 H) and  15  (CAN 1 L). If the difference voltage is above the upper switching threshold, the receiver outputs a signal “0” (dominant). If the difference voltage is below the lower switching threshold, the receiver outputs a “1” signal (recessive). The output is made via line  23  for the first CanBus and via line  24  for the second CanBus. 
         [0030]    For each CAN input, the receiver  21  in  FIG. 4  comprises a comparator  25  (“CAN1”) and  25 ′ (“CAN2”). These are connected to the input terminals “BP/CAN1H”, “BM/CAN1L” and “CAN2H, CAN2L”. As already mentioned, external interconnection (shorting) now makes it possible to implement either a FlexRay receiver in the first mode of operation or two CAN receivers in the second mode of operation. 
         [0031]    The digital output signals  26  . . .  29  from the comparators  22 ,  25  and  25 ′ are forwarded via control block  20 ′ to the terminals  23 ,  24  for appropriate connection to the microcontroller. In the mode of operation as a FlexRay receiver, the signal RX 1  is interpreted as RX and the signal RX 2  is interpreted as RxEN. In the mode of operation as a CAN receiver, RX 1  is interpreted as RX for CAN 1  and RX 2  is interpreted as RX for CAN 2 . 
         [0032]      FIG. 5  shows a further circuit example for a universal receiver  21 ′ with two modes of operation. The bus signals are decoded by means of two comparators  22  and  22 ′, the inputs of which are electrically connected to bus terminals  13  . . .  16 . In this case too, external interconnection of the terminals  13  . . .  16  needs to be performed in the “FlexRay(R)” mode of operation. The first input  37  of the comparator  22  is supplied to a changeover switch  38 , so that this comparator input  37  can be connected to terminal  13  or to terminal  14  depending on the mode of operation. Control line  39 , which is routed from decoder  20 ″ to changeover switch  38 , takes the mode of operation as a basis for selecting the position of the switch  38 . In “CAN” mode, terminals  14  and  15  are connected to bus line “CAN1” and terminals  14  and  16  are connected to bus line “CAN2”, and switch  38  sets up a connection from line  37  to terminal  13 . In the mode of operation as a FlexRay(R) receiver, the terminals  13  and  16  are shorted, as are terminals  14  and  15  (dashed bridges  35  and  36 ). In this mode of operation, switch  38  sets up a connection from line  37  to terminal  14 . Decoder  20 ″ comprises an SPI input  19 ′ which can be used to program the mode of operation of the decoder. In line with the programmed mode of operation, the digital outputs  23  and  24  are used to output either FlexRay(R) data (mode 1: outputs “FR” and “FR-RXEN”) or CAN data (mode 2:outputs “CAN1” and “CAN2”), with two CAN connections being available in the “CAN” mode of operation. 
         [0033]    The conventional, commercially available FlexRay(R) transmission/reception chip  30  (FlexRay(R) transceiver) shown in  FIG. 6  is used as a CAN chip merely by virtue of the actuation/interconnection being adjusted. This is surprisingly possible without excessive losses in terms of signal quality, by virtue of the bus lines “CAN-H” and “CAN-L” of a CAN network being connected to the FlexRay(R) connections  31  and  32 . In addition, output “RXEN” of the FlexRay(R) transceiver  30  is electrically connected to input “RX” of the CAN controller  33 , and input TXEN of the FlexRay(R) transceiver  30  is electrically connected to output “RX” of the CAN controller  33 . The potential at input “TX” of the FlexRay transceiver  30  is connected to a positive voltage V + . The potential at input “RX” of the FlexRay(R) transceiver  30  is connected to a reference-ground potential. This interconnection of the FlexRay transceiver  30  allows the functionality of a CanBus to be reproduced in the simplest way. The multiple use of the circuit provided per se for FlexRay allows a significant savings effect to be achieved in a controller which needs to be provided for both bus standards. 
         [0034]    In at least one aspect, the invention therefore also relates to the use of a FlexRay(R) receiver as a CanBus receiver or of a FlexRay(R) transmitter as a CanBaus transmitter or of FlexRay(R) transceiver as a CanBus transceiver. The FlexRay(R) chip used for this is preferably used without alteration in comparison with FlexRay(R) chips used as standard, only the external interconnection of the connections having been changed in comparison with the interconnection provided in the FlexRay(R) standard. 
         [0035]    On the basis of an example—not shown—of a combined transmitter/receiver circuit (transceiver) that can be used on a modular basis, said circuit comprises a combination of the transmission circuit  12  shown in  FIG. 3  and the reception circuit shown in  FIG. 4 , which essentially comprises the comparators  22 ,  25  and  25 ′. The transmission and reception circuit elements are, in particular, combined to form a common module or electronic chip. An alternative implementation option for a combined transmission/reception circuit of this kind is achieved by combining the transmitter in  FIG. 3  with the reception circuit shown in  FIG. 5 . 
         [0036]    The control logic of blocks  20  and  20 ′ or  20 ″ is expediently combined to form a common block.