FR2807175A1 - METHOD AND DEVICE FOR ESTABLISHING A COMMUNICATION AND LOADING THE DATA OF PARTICIPANTS IN A BUS SYSTEM - Google Patents

Abstract

Method and device for establishing communication between two participants of a bus system which loads into a memory of a first participant the data transmitted from a second participant, at a predetermined operating transmission speed, valid for all participants, each participant in the bus being able to transmit a frame each having a characteristic with the same rights, and determines and receives by the characteristic the frame which is intended for it. The first participant receives at least one frame sent by the second participant at a transmission speed different from the predetermined speed. Sync, One, and Zero frames are defined to fulfill a launch condition in a data loading program.

Description

STATE OF THE ART

  The invention relates to a method and a device for establishing communication between two participants of a bus system and for loading data by the bus system, according to which: - the data is loaded into a memory of a first participant and data is transmitted from a second participant, - the bus system having a predetermined transmission speed, valid for all participants, to which all participants in operation communicate, - data transmission is made in the form of frame and such a frame contains a characteristic according to which each participant in the bus can transmit frames with the same rights and each participant calculates and receives the frame which is intended for him by means of the characteristic. Such a known transmission speed or baud speed, agreed between all the participants in a bus system, and which remains invariable in normal operation, is presented in the case of a CAN bus system;

  it is important for the operation of the CAN assembly.

  This corresponds to the CAN specification of Robert Bosch GmbH from 1991, versions 1.2 and 2.0. The CAN bus has been confirmed as a means of transmitting data at high transmission speed and very high transmission security. The above document describes a serial communication bus, whereby data is transmitted in packets or called frames

  CAN frames which consist mainly of a character

  or identification (ID) and a number

data bytes including 8.

  The ID identification is used here for the

  priority of data packets for bus arbitration.

  Bus arbitration or more simply arbitration means that each time the bus system (or the bus) is free, each participant can transmit information, in particular data. When two or more participants start data transmission at the same time, the use of the characteristic resolves the access conflict to the bus by comparing the transmitted level of information in binary code, i.e. the bit level transmitted by each participant at the bit displayed on the bus. If the levels are identical, the participant can continue

  to issue. One level is recessive and the other is dominant.

  When a recessive level is issued and the bus displays a dominant level, the arbitration participant has lost and must immediately stop its transmission. This is true for the basic CAN system. In the case of the complete CAN system, a differentiation mechanism is applied according to which there is a level or bit comparison concerning the identifier. In addition, there is no longer a distinction between the basic CAN system and the complete CAN system, since the following explanations can be applied or easily transposed. To load data, in particular program codes, the mechanism of a "Bootstrap-Loader" or boot program is known. This boot program is a special program which is put in a memory at the start of the computer system and which then ensures that the parts of the operating system necessary for the implementation of the installation, arrive in the working memory and provide control. A computer system whose operating program is not fixedly wired or contained in a read-only memory (ROM) is only operated by such a mechanism. Such a seed program mechanism for participants in a

  bus system is described in document EP 0 364 127 Ai.

  According to this document, a distinction is made between a loading path for a defined and undefined boot program. The defined path is executed if the current system configuration corresponds to the system configuration planned for the defined loading path. Otherwise, the undefined boot load path is selected, according to which a central service module searches for possible boot load paths to thus start the system. So the whole system is put in

  works through the bootstrap program.

  If in a system combination, different participants, in particular vehicle control devices, must be restarted by another participant, in particular a control and / or programming system for a priming mechanism, in particular in bus systems with of the participants having the same rights, one encounters the problem that an unwanted intervention in the program in particular in the program code of other participants could be made then generating errors. In a CAN bus system or a CAN combination, this must be done individually and thus in a very specific way by adaptation to each bus system in the form of high-level programming. Such high level programming could only be used for the CAN system concerned but not in general. The state of the art also shows that there is no authorization check for such a boot program, so that there may be faults in

  particularly programming faults.

  Serial interfaces (ISO-K) which can be connected in general, between a control device and a control and / or programming system, are known and use a transmission medium such as a boot program. The program to be executed by this transmission medium is thus transmitted and is predefined from the outside without any authorization check. The use of a fast interface, in particular a CAN interface, without using circuit launching conditions

  is not presented in this document.

  It has been found that the state of the art cannot give optimum results in each case. Under these conditions, the purpose of the present invention is to develop a method and a device making it possible to define a bootstrapping program mechanism of universal application, in particular with authorization control for a fast interface, in particular CAN, which can be started without conditions

  launching of specific circuits.

ADVANTAGES OF THE INVENTION

  To this end, the present invention relates to a method of the type defined above, characterized in that the first participant receives a frame from the second participant if the latter sends at least one frame with a transmission speed different from the predetermined operating transmission speed. through the system

of bus.

  According to other advantageous characteristics of the method: the information transmitted by the bus system is in binary code, one level being dominant and the other level being recessive, and the at least single frame having a different transmission speed begins with a predetermined number of dominant levels, including five; - At least two frames are transmitted with a transmission speed different from the predetermined operating transmission speed from the second participant, a first transmission speed of a first frame being distinguished from a second transmission speed of one second frame and the characteristics of the two frames starting with the same number of dominant levels, the first frame, transmitted at the first transmission speed, globally transmits with the dominant levels the binary coded information of a dominant level, and the second frame transmitted at the second transmission speed transmits globally with the dominant levels the binary coded information of a recessive level, the first or the second frame being transmitted one after the other depending on the information to transmit; - the first participant uses a boot program mechanism to load the data, the second participant transmitting to the first as a launch condition in the boot program mechanism, the at least single frame having the transmission speed different from that expected for the bus system; - a third frame is transmitted at a third transmission speed by the second participant to the first participant, the first and the second participant being synchronized on the dominant levels in the third frame, - a fourth frame is transmitted at a fourth speed of transmission, the characteristic of the fourth frame being transmitted with the first and second frames before the transmission of the fourth frame by the second participant to the first participant, the second participant transmitting the data to the first participant after the fourth frame; the fourth frame contains, in addition to the characteristic of the second participant, also a characteristic for the first participant, and a starting address relating to the data to then be loaded into the memory of the first participant; - the first, second, third, and fourth transmission speeds are different and differ from a predetermined transmission speed of the bus system in operation, the fourth speed at which in addition to the fourth frame, the data of the second to the first participant being greater than the first, second and third transmission speed. The different transmission speed is advantageously used as a launch condition in data transmission, in particular in a boot program mechanism for the first participant. Advantageously, it is possible to establish a boot program mechanism of universal application for bus systems each having a predetermined, clean baud rate (baud rate), in particular with authorization control for a CAN bus system. . After acknowledgment of receipt by the first participant, for example a motor vehicle control unit with acknowledgment of receipt, there is transmission of data, in particular of a program code to be executed, in a memory of the first participant. After verification, in particular verification by checksum, the loaded data is executed, for example when it corresponds to a program. This makes it possible to advantageously load any data or program codes into a memory of the first participant and to ensure execution thereof, so that the method and the device are suitable not only for example for low-level programming (for example Flash memory), but also to the analysis and verification of the first participants, also

  regardless of their actual function.

  If advantageously, as a launch condition, only transmitted frames are used, in particular CAN frames, it is possible advantageously to waive any particular HW launch condition while

  retaining all the advantages of a fast bus interface.

  The programming time is thus advantageously shortened The invention also relates to: - a device comprising a first and a second participant and a bus system which connects them, with means for establishing communication between the participants and loading data by the bus system, the data being loaded into a memory of the first participant and the data being sent by the second participant, the bus system having a predetermined transmission speed and valid for all participants, and to which all the participants communicate by operation, the transmission of the data being made in the form of frames and such a frame containing a characteristic, each participant of the bus being able to transmit frames of the same right and each participant determining by the characteristic, the frame which is intended for it and receiving it, characterized in that other means are contained in the second participa nt and the first participant receives frames from the second participant when the second participant transmits by other means, at least one frame at a transmission speed different from the transmission speed predetermined by the bus system; a control device as the first participant of a bus system, the bus system transmitting data to the control device and the latter transmitting data by the bus system, the bus system having a transmission speed predetermined valid for all participants, to which all participants communicate in operation, the data transmission being in the form of frames and such a frame containing a characteristic, each participant being able to send frames with the same rights, and each participant determining and receiving the frames which are intended for it using the characteristic, characterized in that the control apparatus comprises a priming program and means which can determine at least one frame at a transmission speed different from the speed of predetermined transmission and which then activate the boot program; - a verification and / or programming system as second participant of a bus system, the bus system transmitting data to a first participant by the second participant, the bus system having a predetermined transmission speed and valid for all the participants, to which all the participants communicate in operation, the transmission of the data being done in the form of frames and such a frame containing a characteristic, each participant sending frames of the same right and each participant determining and receiving the frames which are intended for the aid of the characteristic, characterized in that the second participant contains means which form and transmit to the first participant at least one data frame at a transmission speed different from the predetermined transmission speed, and the data are then transmitted to the first participant; - a bus system for transmitting data to a first participant from a second participant, the

  bus system with a predetermined transmission speed

  completed valid for all participants, to which all participants communicate in operation, the transmission of data being in the form of frames and such a frame containing a characteristic, each participant being able to send frames with the same rights and each participant determining and receiving the frames intended for it using the characteristic, characterized in that frames are defined in the bus system to be transmitted by the bus system at at least one transmission speed

  different from the predetermined transmission speed.

  Advantageously, it is thus possible to use the boot program mechanism in each bus environment, in particular a CAN environment, that is to say either in a separate control device with CAN interfaces or a CAN combination, but also in a vehicle or machine tool, and adaptation can be envisaged for application to different networks, from the point of view of

  Baud rate and / or ID identifications used.

  In particular, it is possible to envisage the use of several alternating baud transmission speeds, in particular low, to use complete frames as information carriers which cannot be parasitized, which offers important advantages for

solve the problem.

DRAWINGS

  The present invention will be described below in more detail with the aid of the appended drawings in which: - the figure shows a circuit comprising a control device and a PPS control and / or programming system, which can be connected by a bus system or a corresponding interface, in particular a CAN system, - Figure lb shows a combination of system in a vehicle, to which a PPS control and / or programming system is coupled by a bus system, in particular a CAN system , - Figure 2 shows the execution of the method according to the invention for a BSL boot program in particular by a CAN bus in the form of a flowchart, - Figure 3 shows the ESB launch conditions or the frames corresponding to these with variable speeds, - Figure 4 shows by way of example the definition of different frames for a CAN boot program, and - Figure 5 shows the progress of a programming

  control device in the form of a flow chart.

  The present invention will be described below in

  using an exemplary embodiment. In this description,

  to explain, a CAN bus system is used. However, the invention can be applied to any bus system presenting a comparable situation such as a combined CAN system, from the point of view of the boot mechanism or

launch conditions.

  DESCRIPTION OF THE EXAMPLE OF IMPLEMENTATION

  FIG. 1a shows a control device 100 connected by a CAN bus system 107 or an interface corresponding to a CAN bus system with a PPS 108 programming and / or control system. The PPS 108 system has an interface 106 to be connected to the CAN bus. Such an interface 105 for the connection with the CAN bus 107 is also provided in the control device 100. The reference 102 designates the working memory RAM of the device

  control. This can be provided in the micro-

  computer pC 101 of the control unit or be outside of it. The same remark applies to memory 103 which is also a non-volatile memory. This

  non-volatile memory 103 can be rewritable, i.e.

  say erasable or non-erasable. According to the realization of the memory 103, as an option, there is another memory 104 also

  nonvolatile. Reference 101 corresponds to a micropro-

  stopper. Depending on the extent of the functionalities and the embodiment, this is also a pC microcomputer, a microcontroller or the like. The memories 102, 103 and optional 104 as well as the interface 105 and at least one calculation unit 101 of the control device 100 are connected by an internal bus system 115. Any other elements contained in the device such as computing units, memory, interface, power supply, etc.

  are not shown for the sake of simplification.

  FIG. 1b shows the control device 100 integrated in a vehicle 110 and connected by a CAN bus system 111 with optional other control devices, actuator sensors, interfaces, etc., by a CAN bus system 111. An element 109 diagrams the other elements connected to the CAN bus 111. A connection interface on the CAN bus 111 has the reference 112. On this interface 112, it is possible, for example, to connect a PPS 114 control and / or programming system, in particular without its own interface , through

  a link 113, bidirectional with the CAN bus.

  The connection interface can be integrated into the CAN bus by

  the PPS 108 system or be external like the PPS 114.

  The definition according to the invention of a universal CAN boot program (CAN-BSL), in particular with authorization control, must be carried out for example by low level programming even by the CAN-BSL system, to shorten by example the programming times of a control apparatus 100. In addition, it is also possible, for example, to carry out a control of the control apparatus (analysis) by this procedure, independently of the function proper of the control apparatus. The mechanism discussed below can thus be used in a separate control device but also in a vehicle control device. Unlike programming or high-level transmission, with low-level programming, there is a simple transmission to the plane of the components without requiring complicated program structures in the control unit. This means that specific and complicated program protocols for the communication plan with a complex environment such as a main part and a priority part are thus avoided. In particular, low-level programming or communication is oriented according to the possibilities of the machine and not directly according to the

user-defined program.

  The boot program is stored either in a non-volatile memory 103, 104 as a program code to be loaded from there into the active memory 102 of the control unit 100. It can also be a program wired into a state machine, like automaton contained directly in the microprocessor pC 101. The boot program can be housed in a simple read only memory (ROM) 104 to be loaded with a view to its execution in an active memory. Likewise, provision may be made in a reserved and protected area of a non-volatile memory 103, for example in the form of a PROM, EPROM, EEPROM, Flash-EPROM memory etc; But

  for this, we will not use memory 104 of ROM type.

  The BSL universal CAN boot program in a control unit is activated by the transmission of a start condition, in particular a CAN start condition, ESB. The information contained in the CAN launch condition, ESB is used to configure the rest of the CAN communication. We can thus adapt the process to its application to different CAN networks according to the baud rate and the ID identifier. After confirmation of receipt by the receiving device using the acknowledgment of receipt, the program code to be executed is transmitted to the working memory of the control device, i.e. the RAM memory 102. After authorization check, for example by a checksum calculation, the loaded program is executed. Figure 2 shows a flow chart for this purpose. The programmed system PPS 108 or 114 works as a master and the control unit SG 100 as a slave. Block 101 supplies power to the control device; block 200 starts programming or implementing the boot program. The master, that is to say the PPS system sends in block 202, the ESB start condition to the slave, that is to say the SG 100 control unit.

  is represented by the passage PPSl.

  Interrogation 203 checks whether the start condition of the master has been recognized or whether it exists. If not, go to block 204 and normal operation of the control unit. On the contrary, if the launch condition is recognized, we go to block 205 which acknowledges the control unit by an acknowledgment of receipt. The transmission of the receipt is represented by SG1. Then in interrogation 206, it is checked whether the master has thus

  received acknowledgment of receipt of the control device by PPS.

  If not, we go back to block 202 and we issue the launch condition again. In case of

  reception of the acknowledgment, we go to block 207.

  After sending the acknowledgment from the control unit in block 205, the control unit triggered by the ESB launch condition triggers the boot program in the active memory (RAM) 102 of the control unit 100. As already indicated in this block 208, the boot program can be activated even if it exists in the form of a state machine in the microcomputer 101. The boot program then ensures the transmission of CAN data, that is to say the transmission in particular of the programming routines in the active memories (RAM) 102 of the control apparatus 100. This

  transfer is represented by PPS2.

  In block 209, the active memory is checked, for example by forming a checksum. Using a CAN bus, the CAN protocol checksum mechanism can be used. If, upon verification of the checksum of the active memory, a fault is encountered, the error can be treated using the CAN bus according to the CAN procedure and this is why this procedure will not be detailed. In case of error, we simply repeat the routines by loading them into the active memories to replace the

  defective elements by a return designating the defects.

  If the checksum check is in order, we go to the program loaded in the active memory in block 210. From the cut-off point Al to the cut-off point A2 in block 210, we go to execution from the non-volatile memory of the control device, in particular from the ROM memory or from the reserved flash range (see above). From the point of intersection A2, the rest of the process is executed from the working memory (RAM) 102 of the control apparatus. After the start of the working memory routine in block 210 and the execution or the start of execution or a first routine run, in block 210, a confirmation of the control unit is again sent as acknowledgment of receipt. The transfer to the master represented by SG2 again requires verification in the interrogation 212 to know whether the acknowledgment of receipt of the control apparatus has been received. If not, return to block 207 and transmit the programming routines again to the active memory. We avoid going through a final loop

  by limiting loading attempts.

  If the confirmation from the control unit is received, go to block 213 for the start of CAN transmission. If the programming is a flash programming, the flash data is then transmitted in block 213. The non-fleeting memory 103 can also be produced as flash memory. The flash data is received by the control unit to undergo a

  verification such as a checksum verification.

  If the verification is in order, we program the data

  flash in the flash memory. This is done in block 214.

  In the event of an error in checking the data or verifying the checksum, the respective data can be transmitted again. By programming or when the programming of the flash data is completed, a confirmation is sent again by the control unit. This is

done in block 215.

  The transfers from the PPS master to the control unit, i.e. here the transmitted flash data, are represented by the PPSK passages. The transmission of the confirmation from the control unit is represented by transfer SG4. For security reasons and by limiting the maximum content of the data in a CAN frame, portions of flash data are formed, that is to say parts of the data are transmitted. The execution of the process from the cutoff point A3 to the cutoff point A4 is thus repeated for each transmitted part of the flash data. For reasons of clarity, the new verification of the acknowledgment of receipt of the control device is not presented in detail. The master checks with the acknowledgment of receipt whether the last transmitted flash data is programmed or not and it sends for example the following data only after an acknowledgment of receipt. If there is no acknowledgment from the control unit for the last flash data packet, unscheduled flash data, i.e. data not confirmed by acknowledgment of receipt, is transmitted again. When the CAN transmission of the flash data in block 213 is finished, we pass to block 216, that is to say the end of the operations. By loading the routines, in particular the programming routines in the memory (RAM), the execution is carried out from the cut-off point A2 to the cut-off point A4 from the active memory of the control device. Thus, the flash programming routines are loaded by the CAN boot program into the RAM memory internal to the control unit; a checksum check is also performed in this way and executed. The programming verification system will only have to supply the control unit and generate the CAN launch condition (CAN-ESB), then transmit the data (flash programming routines and flash data) by the

CAN system.

  Using the method as presented, it is possible in principle to load any code into the active memory of the control device and execute it. The method can thus be used not only for low-level flash programming, but also for analysis and

  checking the control unit.

  The decisive element for the application of the method to a CAN system or comparable to a CAN system is the condition for launching ESB in the boot program mechanism. On the one hand, the advantages of the fast interface (for example in Mbaud) are used without any conditions for launching a circuit. As an ESB condition, only the CAN frames transmitted are used. However, this launch condition or the CAN frames used must not occur in normal operation, because otherwise the risk of a disturbance is great since by setting the transmission speed or baud rate in the CAN system and giving the same rights to participants in programming a vehicle program system,

  would intervene in the driving program.

  Since CAN IDs are system specific, that is, assigned unique to each CAN system, they cannot be used in general CAN boot loader mechanisms with

  corresponding launch conditions.

  The solution according to the invention lies in the use of variable baud rates, in particular low baud as CAN launch conditions. A conventional CAN system does not respond to variable baud rates, particularly low. In addition, to increase the data transmission speed in the future, another increase in the CAN baud rates used is expected. As in a CAN system, the dominant state of the bus is imposed (dominant state of the bus, i.e. for example the low level), the CAN frame with more priority zeros in the identifier ID will have the highest priority. For synchronization reasons, inside a CAN frame, after a determined number of bits of the same level, in particular after a maximum of 5 bits, a change of edge is always inserted, which is called bit stuffing in the CAN system. Normally this bit stuffing is cleared again when the information is used. To establish a master / slave type communication via the CAN bus, with the participants having in fact the same rights, three frames are defined for this, namely a Sync frame, a One frame and a Zero frame. Figure 3 shows this situation. The start of CAN-ESB frames is also called Info phase and thus represents a signal which cannot be disturbed or exchanged.

  thanks in particular to the five dominant bits.

  FIG. 3 shows for the AtO cutoff until the At2 cutoff, a first frame, that is to say the Sync frame transmitted by the master with a baud rate of transmission 1. The Info phase is defined from the time segment AtO up to the Atl time segment and with IPSync. In IPSync, we transmit

  thus five bits with a dominant rate at baud rate 1.

  In the next part called RestSync, between the segment Atl up to the time segment At2, there will only be the condition of not having successively five bits of the same level positions, in particular of dominant positions which follow one another; this will be detailed with the aid of FIG. 4. The frame Un, which transmits for the establishment of the communication either the state "1", or the high level information, corresponds to the time segment comprised between At3 and At5. This transmission takes place at baud speed 2. The Info phase has a duration ranging from the At3 cutoff to the At4 cutoff time and bears the designation IPUn. In this case, five identical bits are also transmitted in particular of dominant level at baud rate (2) by the master. The other bits of frame One are grouped in Restun between the instant At4 until the instant At5; the same considerations for successive bits of the same level as for the Sync frame apply here. Finally in FIG. 3, the zero frame is shown, the bits of which are transmitted at baud rate 3 and which transmits the zero information (low) for the establishment of the communication. Between the time cuts At6 to At7, we also transmit here in the IPZero Info phase, of the Zero frame, five bits of dominant level, namely at baud rate 3 by the master. The other bits of the Zero frame are grouped in RestZero between At7 and At8; the same considerations as for RestSync and RestUn apply here. Depending on the definition of the frames used for Sync, One and Zero, you can modify the respective importance of Restbits, RestSync, RestUn and RestZero. The decisive elements in this case are the info, IPSync, IPUn or IPZero phases with the dominant level bits, successive notably five bits. These phases are used in the rest of the communication with different baud rates 1, 2, 3 as information carriers. The use of these baud rates, which are notably different, gives different durations with which the information for the other CAN communication is transmitted at the same time as CAN-ESB, that is to say with a higher baud rate. . For security reasons, we can fix that the Rest of the respective CAN frames RestSync, RestUn, RestZéro corresponds to a maximum of three successive bits of dominant level if due to bit stuffing after five bits, we will have formed the Info phase with five dominant bits. This means that the sequence of bits

  dominant longest in the Rest of CAN frames, that is

  ie RestSync, RestUn or RestZéro, that is to say at the lower baud rate, must in no case lead to confusion with in particular the five dominant bits of an Info phase. This is ensured in the example of the table in the

figure 4.

  In FIG. 4, four different CAN frames have been defined. These are frames called Sync, One, Zero and then the trigger frame. As from the most different ESB-CAN frames in particular we consider the lowest baud rate Sync, One and Zero, only the Info phase as reliable information of a CAN message, because the following bits can be disturbed, we use this part as support. Using this medium, n information bits are transmitted which are defined in the following trigger frame. This will be presented later using the

figure 5.

  The process can thus be adapted to different CAN networks for baud rate and for the identifier. As an example, in table T400 of FIG. 4, CAN-ESB has been defined as a cyclic sequence of CAN frame transmitted by PPS as master. The conditions for the derivation to the CAN boot program are almost included in the identifier, indirectly in the data content, the baud rate and the sequence of CAN messages. Table T401 contains, for example, the CAN frames of the master with the frame names Sync, Un, Zero and triggering. For Sync, One and Zero frames, it suffices to fulfill three conditions. On the one hand with a number of dominant bits, in particular five, the identifier is introduced. Secondly, that is to say in the Rest of the identifier and in the content of the data, care is taken to ensure that this constellation of the five particularly dominant bits does not occur any more. Third, the three frames are transmitted at different transmission speeds, in particular at baud rates 1, 2, 3 as shown. For example, the baud rates are in particular low baud rates compared to a usual transmission speed such as Mbaud. These are for example between 38 and 47 kilobaud. In an example, one could provide for speed 1, 38.27 kilobaud, for speed 2, 42.10 kilobaud and for speed 3, 46.78 kilobaud. The trigger frame is specified by alternating frame One and Zero as shown in the figure, bearing as identifier, the CAN launch program master identifier (CAN-BSL-master-ID) which can be used for code block data and data

flash.

  The data content in this example has a reserved byte at the beginning and at the end each time and in addition the CANBSL slave ID identifier for the control device, for example two bytes for the RAM start address as well as two bytes for the RAM end address (replacing the start address plus the offset address) and the baud rate R is transmitted with the transmission rate. The baud rate R is also distinguished from the predetermined transmission speed usually in

each CAN system.

  For example, for a transmission speed in normal operation of 1 megabaud, the trigger could transmit at a speed of 500 kilobaud. It is avoided that for example in a device of

  ordering a vehicle, you request the walking program.

  If the CAN-ESB is recognized by the control unit, it

  this responds with an acknowledgment frame presented in Table T402. This acknowledgment frame contains as identifier, the identifier ID-slave-CAN-BSL and in the data content, one byte of error code and four bytes corresponding to the mask version for basic CAN. In addition, three bytes are reserved for example. The acknowledgment frame from the slave, that is to say from the control unit, is also transmitted at speed R to the master. The 11-bit identifier can in particular be stored in bits ID 28 to ID 18 of a CAN frame in standard format. This can simply be transposed to the format

extended.

  Figure 5 again shows a flowchart in a program system for the master with specification of trigger frames. Starting from segment A50 to segment A51, a Sync 500 frame block is transmitted at the start of the process. This Sync frame wakes up the slave, that is to say the control unit. From segment A51 to segment A52, there will then be n alternating frames, One frames or Zero frames to transmit n bits of information for the rest of the communication specifications. In block 501, a number nb of frames is transmitted for bit stuffing, in particular the information concerning the baud transmission speed of the following trigger frames or acknowledgment frames. In the particular example, for example nb may be 15. This thus makes it possible to transmit 15 state frames One or zero-state at 15 bits with the information for the baud rate used later. In block 502, the CAN-BSL master ID identifier is then transmitted with neither frames. In the present example, an 11-bit identifier was used; the identifier ID with for example 11 bits, that is to say ni = 11 frames would thus be transmitted. In block 503, there are then still nc frames for verification in particular to form a checksum. Using a Nibbel-XOR checksum, for example, we would have nc = 4. Here we transmit four bits in four One or Zero frames in block 503. A nibbel is half a byte; a nibbel is coded in hexadecimal. This corresponds to a preferential writing for the content of the memories. We have thus transmitted in blocks 501, 502, 503, in a concrete example 15 + 11 + 4 = 30 bits with n = 30 frames. Each zero frame thus represents "zero" information (0) and each one frame represents a "one" state.

(1).

  From cut A52 to cut A53, the transmission of the trigger frame is ensured by a new Sync frame in block 54. Blocks 500 to 504 or the frames sent in these blocks have a special feature since the master does not wait for circuit acknowledgment bits. Due to the absence of circuit acknowledgment bits, a consecutive reset of the CAN system (Reset) or of these blocks 500-504 is required. CAN-ESB is thus defined as a cyclic CAN frame sequence transmitted by the PPS master. From segment 53 to segment 55, the transmission and transmission of the trigger frame are then ensured. From segment 54 to segment 57, at the high speeds R transmitted in block 501, we pass to 500 kilobaud. In block 505, the trigger frame is then transmitted with the identifier ID-slave-CAN-BSL + the start address RAM + the final address RAM to the slave; this frame is characterized by its ID-slave transmission. The slave then transmits its acknowledgment frame to the master as shown in FIG. 4, after reception of the trigger frame. The master waits between segment 55 and segment 56 for the response from the control device, in particular with a time count, that is to say a waiting time TW. This is done in question 55. If the answer from

  the control unit with the identifier ID-slave-CAN-

  BSL arrived during the waiting time PW, we start in block 507 with CAN transmission at the agreed baud rate, for example R of information from the master to the slave. If the master does not receive an acknowledgment from the slave, we start again by sending a SYNC frame in block 500 and we thus repeat the ESB input condition. The waiting time for the TW countdown can thus correspond to 2 milliseconds. If CAN-ESB is then recognized by the control unit, it responds with an acknowledgment frame. The important thing here is that the transmitted speed and the CAN-ID do not overly code the control unit but inform the control unit with the launch conditions. The continuation of the CAN transmission in block 507 then occurs at a high baud rate R in particular for example 500 kilobaud and uses the two master identifiers-CAN-BSL for the transmission.

  between master and slave and ID-slave-identifier

  CAN-BSL for the transmission from the slave to the master. The method and the device according to the invention thus make it possible, in the same bus system, with participants having the same rights and for the transmission speed provided for

  operation, to carry out a master communication

  slave between two participants without having a fault or

  disturbances for the whole system.

  As an advantageous development, the entire transmission can be defined in the form of an NOP file as an extension for CAN; this allows for simple specification. The NO protocol communication folder (NOP folder) describes the data flow of a serial communication. In addition to the data itself, it also contains the

  description of the communication and the configuration of

  the interface. Using this folder, data can be transmitted for flash programming of a control device via the serial data line. It is thus possible to describe in a uniform manner different protocols. This file can be generated automatically by predefining the protocol to

  to describe. In this case, it is CAN.

Claims (9)

R E V E N D I C A T IONS   1) Method for establishing communication between two participants of a bus system and for loading data by the bus systems, according to which: - the data is loaded into a memory of a first participant and the data is transmitted from of a second participant, - the bus system having a predetermined transmission speed, valid for all participants, to which all participants in operation communicate, - the data transmission is made in the form of a frame and such a frame contains a characteristic according to which each participant in the bus can transmit frames with the same rights and each participant calculates and receives the frame which is intended for him by means of the characteristic, characterized in that the first participant receives a frame from the second participant if the latter sends at least one frame with a transmission speed different from the predetermined operating transmission speed through the system of bus.   2) Method according to claim 1, characterized in that the information transmitted by the bus system is in binary code, one level being dominant and the other level being recessive, and the at least single frame having a speed   of different transmission begins with a predetermined number of dominant levels, including five.   3) Method according to claim 2, characterized in that at least two frames are transmitted with a transmission speed different from the predetermined operating transmission speed from the second participant, a first transmission speed of a first frame is distinguishing from a second transmission speed a second frame and the characteristics of the two frames starting with the same number of dominant levels, 5 the first frame, transmitted at the first transmission speed, globally transmits the information with binary coding of a dominant level, and the second frame transmitted at the second transmission speed globally transmits with the dominant levels the binary coded information of a recessive level, the first or the second frame being transmitted in succession l 'a   on the other according to the information to be transmitted.   4) Method according to claim 1, characterized in that the first participant uses a boot program mechanism to load the data, the second participant transmitting to the first as a launch condition in the boot program mechanism, the frame at less unique with different transmission speed than expected for the bus system.    ) Method according to claim 3, characterized by a third frame transmitted at a third transmission speed by the second participant to the first participant, the first and the second participant being synchronized on the dominant levels in the third frame. 6) Method according to claim 3, characterized in that a fourth frame transmitted at a fourth transmission speed is defined, the characteristic of the fourth frame being transmitted with the first and second frames before the transmission of the fourth frame by the second participant to the first participant, the second participant transmitting the data to the first participant after the fourth frame.   7) Method according to claim 6, characterized in that the fourth frame contains in addition to the characteristic of the second participant also a characteristic for the first participant, and a starting address concerning the data to be loaded then into the memory of the first participant.   8) Method according to any one of claims 3 to 5, 6,   characterized in that the first, second, third, and fourth transmission speeds are different and differ from a predetermined transmission speed of the bus system in operation, the fourth speed at which, in addition to the fourth frame, the data from the second to the first participant, being greater than the first, to the   second and third transmission speed.   9) Device comprising a first and a second participant and a bus system which connects them, with means for establishing communication between the participants and loading data by the bus system, the data being loaded into a memory of the first participant and the data being sent by the second participant, the bus system having a predetermined transmission speed valid for all the participants, and to which all the participants communicate in operation, the data transmission being made in the form of frames and such frame containing a characteristic, each participant of the bus being able to transmit frames of the same right and each participant determining by the characteristic, the frame which is intended for it and receiving it, characterized in that other means are contained in the second participant and the first participant receives frames from the second participant when the second participant tr ansmet by other means, at least one frame at a transmission speed different from the transmission speed   predetermined by the bus system.    ) Control device as the first participant in a bus system, the bus system transmitting data to the control device and the latter transmitting data via the bus system, the bus system having a predetermined transmission speed valid for all participants, to which all participants communicate in operation, the transmission of data being in the form of frames and such a frame containing a characteristic, each participant being able to transmit frames with the same rights, and each participant determining and receiving the frames which are intended for it using the characteristic, characterized in that the control apparatus comprises a priming program and means which can determine at least one frame at a transmission speed different from the transmission speed predetermined transmission and which then activate the boot program.   11) Verification and / or programming system as second participant of a bus system, the bus system transmitting data to a first participant by the second participant, the bus system having a predetermined transmission speed and valid for all the participants, to which all the participants communicate in operation, the transmission of the data being done in the form of frames and such a frame containing a characteristic, each participant sending frames of the same right and each participant determining and receiving the frames which are intended for the aid of the characteristic, characterized in that the second participant contains means which form and transmit to the first participant at least one data frame at a transmission speed different from the predetermined transmission speed, and the data are   then transmitted to the first participant.   12) Bus system for transmitting data to a first participant from a second participant, the   bus system with a predetermined transmission speed   completed valid for all participants, to which all participants communicate in operation, the transmission of data being in the form of frames and such a frame containing a characteristic, each participant being able to transmit frames with the same rights and each participant determining and receiving the frames intended for it using the characteristic, characterized in that frames are defined in the bus system to be transmitted by the bus system at at least one transmission speed different from the predetermined transmission speed .