JP2004172979A - Method of driving can driver and drive control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of a noise current in a CAN (control area network) communication system having a plurality of CAN buses. <P>SOLUTION: In the CAN communication system 20, communication is done via two CAN drivers 23, 24 connected to two CAN buses 25, 26, respectively. A signal TX1 applied to the first CAN driver 23 is detected, and the CAN drivers 23, 24 are driven on the basis of the detected output of the signal so as to shift a timing when the signal TX1 applied to the first CAN driver 23 varies from a passive state to a dominant state, and from the dominant to the passive from a timing when a signal TX2 applied to the second CAN driver 24 varies from a passive sate to a dominant state and from the dominant to the passive. Consequently, a coincidence in the drive timing between the drivers 23 and 24 can be avoided and thus the influence of a noise current can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drive method and a drive control device of a CAN driver in a CAN communication system that performs communication between intelligent terminals via a plurality of CAN drivers respectively connected to a plurality of CAN buses.
[0002]
[Prior art]
A controller area network (abbreviated as CAN) is a serial bus system suitable for networking and connecting intelligent terminals. In communication between the intelligent terminals in CAN (hereinafter referred to as CAN communication), prioritized messages are transmitted even though there is no address designation of a subscriber or a setting station. By assigning priorities to the messages and transmitting them, it is easy to solve the problem of collision of transmitting a plurality of messages on the CAN bus. Therefore, as described above, the CAN is used to network and connect the intelligent terminals. It is preferably used.
[0003]
FIG. 7 is a system diagram showing a simplified configuration of a conventional CAN communication system 1. In FIG. 7, a CAN is configured between an electronic control unit (abbreviated ECU) 2 mounted on a vehicle such as an automobile and used for controlling the output of an engine, for example, and another control ECU or sensor. An example will be described below.
[0004]
Two first and second CAN buses 3, 4 are connected to the ECU 2 via two first and second CAN drivers 5, 6, respectively. The ECU 2 is a central processing unit 7 (abbreviated CPU) which is an oscillation source of a communication signal and executes a control operation in response to a signal from another ECU or a sensor received through the CAN bus, and a power supply such as a storage battery. It includes a power supply line VCC8 that supplies power to the output, and first to fourth MOSFETs 9, 10, 11, 12 (Metal Oxide Semiconductor Field Effect Transistors) whose gates are connected to the CPU 7.
[0005]
Of the four MOSFETs 9, 10, 11, 12, the first and third MOSFETs 9, 11 have drains connected to the power supply line VCC8 and sources connected to the first and second CAN buses 3, 4, respectively. On the other hand, the drains of the second and fourth MOSFETs 10 and 12 are connected to the first and second CAN buses 3 and 4, respectively, and the sources are grounded.
[0006]
The first to fourth MOSFETs 9, 10, 11, and 12 function as switching transistors in which a current flows between the drain and the source only when a voltage is applied from the CPU 7 to the gate. That is, when a voltage is applied to the gates, current flows from VCC 8 to the first and second CAN buses 3 and 4 in the first and third MOSFETs 9 and 11, respectively, and the first and third MOSFETs 10 and 12 A current flows from the second CAN buses 3 and 4 to the ground to form a circuit. When no voltage is applied to the gate, the current is cut off by the first to fourth MOSFETs 9, 10, 11, and 12.
[0007]
As described above, the power supply from the VCC 8 is turned on / off by the MOSFETs 9, 10, 11, and 12 by controlling the voltage application to the gates of the MOSFETs 9, 10, 11, and 12 by the CPU 7. The ON / OFF signal is input to the CAN drivers 5 and 6 and transmitted to the CAN buses 3 and 4 via the CAN drivers 5 and 6 as a communication signal.
[0008]
Since the first and second CAN buses 3 and 4 have the same configuration, the configuration will be described below with the first CAN bus 3 as a representative. The first CAN bus 3 includes a bus H13, a bus L14, and two terminating resistors 15 connecting the buses H13 and L14. The first CAN bus 3 transmits a communication signal to the terminal on the receiving side by changing the voltage levels of the buses H13 and L14. A state where the voltage levels of the buses H13 and L14 are equal is called passive, and a state where the voltage level of the bus H13 is higher than the voltage level of the bus L14 is called dominant. As described above, the dominant and the passive are formed on the CAN bus 3 by controlling the voltage applied from the CPU 7 to the gates of the MOSFETs 9 and 10.
[0009]
When a voltage is applied from the CPU 7 to the gates of the MOSFETs 9 and 10 and a circuit from the VCC 8 to the first CAN bus 3 and the second MOSFET 10 via the first MOSFET 9 and the first CAN driver 5 is formed, for example, a voltage of 3 to 5 V is applied to the bus H13. A voltage is applied and a current flows through the circuit. When a current flows through the terminating resistor 15 of the first CAN bus 3 having a resistance value of, for example, about 60Ω, a voltage drop occurs, and a dominant in which the bus H13 has a higher voltage than the bus L14 is formed. . In this dominant state, a current of about 80 mA flows through the circuit, but this current acts as noise on the ECU 2 including the power supply line VCC8. As described above, the second CAN bus 4 has the same configuration as the first CAN bus 3, and the communication by forming the passive and dominant is executed in the same manner.
[0010]
FIG. 8 is a timing chart related to passive and dominant formation in the first and second CAN buses 3 and 4. When two CAN buses 3 and 4 are provided as in the CAN communication system 1, the dominant and passive timings formed in each CAN bus sometimes overlap as shown in FIG.
[0011]
As described above, when the potential of the CAN bus changes from passive to dominant and from the dominant to passive, the current flowing in the circuit acts as noise on the ECU 2, so that the timing of the potential change in the two CAN buses 3 and 4 is superimposed. Then, the currents flowing through the respective CAN buses 3 and 4 both act as noise. Therefore, the noise current for the ECU 2 doubles to 160 mA, assuming that the noise current in one CAN bus is 80 mA as described above, for example. If more CAN buses, for example, an ECU has n CAN buses and the timing of potential change in the n CAN buses is superimposed, a noise current of 80 mA × n adversely affects the CAN communication of the ECU. become.
[0012]
Conventionally, a plurality of DC power supply circuits are connected to a DC power supply. For example, in a DC power supply such as a constant voltage generator, the switching operation of switching transistors provided in each DC power supply circuit is shifted from each other, so that the input ripple of the DC power supply is The current is reduced to reduce the noise (for example, see Patent Document 1).
[0013]
[Patent Document 1]
JP-A-5-103465
[0014]
[Problems to be solved by the invention]
However, in the CAN communication system, there is no mention of an adverse effect of a noise current caused by a change in a voltage level forming a communication signal being superimposed on a plurality of CAN buses, and a technique for suppressing the above-described noise current. Has not yet been disclosed.
[0015]
An object of the present invention is to provide a driving method and a driving control device for a CAN driver that can reduce the influence of noise current in a CAN communication system including a plurality of CAN buses.
[0016]
[Means for Solving the Problems]
The present invention relates to a method for driving a CAN driver in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses,
A signal input to one CAN driver selected from the plurality of CAN drivers is detected, and a signal input to the one CAN driver changes from passive to dominant and from dominant to passive based on a detection output. The CAN driver is configured to drive the CAN driver so as to shift the timing at which the signal input to the CAN driver other than the one CAN driver changes from passive to dominant and from dominant to passive. Is the driving method.
[0017]
According to the present invention, in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses, a signal input to one CAN driver selected from the plurality of CAN drivers is provided. The CAN driver shifts the timing at which the signal input to the remaining CAN driver except one CAN driver changes from passive to dominant and from dominant to passive, and the timing at which the signal changes to the remaining CAN driver except one CAN driver from passive to dominant and passive. Driven. Thus, it is possible to prevent the timing of the potential change formed on the CAN bus connected to each of the plurality of CAN drivers from overlapping. Therefore, it is possible to prevent the noise current generated at the time of the potential change in each CAN bus from being added to affect the CAN communication system, and to limit the influence of the noise current generated at the time of the potential change in each CAN bus. Therefore, it is possible to reduce the adverse effect of the noise current.
[0018]
Further, the present invention oscillates a pulse signal based on a detection output of a signal input to the one CAN driver,
With respect to the timing when the signal input to the one CAN driver changes from passive to dominant and from dominant to passive, the signal input to the remaining CAN driver except for the one CAN driver is changed from passive to dominant and from dominant to passive. Is shifted by delaying by a time corresponding to the pulse width of the pulse signal.
[0019]
According to the present invention, the timing at which a signal input to one CAN driver selected from a plurality of CAN drivers changes from passive to dominant and from dominant to passive is applied to the remaining CAN drivers excluding one CAN driver. The difference between the timing at which the input signal changes from passive to dominant and the timing from dominant to passive changes by a time corresponding to the pulse width of the pulse signal oscillated based on the detection output of the signal input to one CAN driver. This is realized by delaying signals input to the remaining CAN drivers except one CAN driver. As described above, the timing of the potential change formed on the CAN bus connected to each of the plurality of CAN drivers by a simple method of using the pulse signal oscillated based on the detection output of the signal input to the CAN driver. Can be prevented and the adverse effect of the noise current can be reduced.
[0020]
In addition, the present invention provides a method wherein at least three CAN drivers are provided.
The pulse width of the pulse signal is
On the basis of the pulse signal, an input signal is set to be different for each CAN driver in which the timing of changing from passive to dominant and from dominant to passive is determined.
[0021]
According to the present invention, when at least three or more CAN drivers are provided, the pulse width of the pulse signal is determined based on the pulse signal. The CAN driver determines the timing at which the input signal changes from passive to dominant and from dominant to passive. It is set to be different every time. In this way, the timing of the potential change of the CAN bus connected to the remaining two or more CAN drivers does not overlap with the timing of the potential change of the CAN bus connected to the one CAN driver. In addition, by a simple method of setting the pulse width of the pulse signal to be different for each CAN driver, it is possible to easily prevent the timing of the potential change in a plurality of CAN buses from being superimposed.
[0022]
Further, the present invention is a drive control device for a CAN driver in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses,
Pulse oscillating means for detecting a signal input to one CAN driver selected from the plurality of CAN drivers and oscillating a pulse signal based on the detected output;
The timing at which the signal input to the one CAN driver changes from passive to dominant and from dominant to passive changes the timing at which the signal input to the own device changes from passive to dominant and from dominant to passive. And control means for controlling so as to delay by a time corresponding to the pulse width of the CAN driver.
[0023]
According to the present invention, in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses, a CAN bus connected to one CAN driver selected from the plurality of CAN drivers. Controlling the driving of the CAN driver so that the timing of the potential change formed on the CAN bus is shifted from the timing of the potential change formed on the CAN bus connected to the remaining CAN drivers except for one CAN driver. A possible CAN driver drive control device is realized. In a CAN communication system including such a CAN driver drive control device, overlapping of timings of potential changes formed on the CAN bus connected to each of the plurality of CAN drivers is prevented, and adverse effects of noise current are reduced.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a simplified system diagram showing a configuration of a CAN communication system 20 including a CAN driver drive control device 21 according to an embodiment of the present invention. The CAN communication system 20 according to the present embodiment exemplifies a system that performs CAN communication between an ECU 22 mounted on a vehicle and another ECU or sensor mounted on the same vehicle, for example.
[0025]
Two first and second CAN buses 25 and 26 are connected to the ECU 22 via two first and second CAN drivers 23 and 24, respectively. Thus, the CAN communication system 20 has two communication channels. The ECU 22 is an oscillation source of a communication signal and includes, for example, a microcomputer including a CPU 27 that executes a control operation in response to signals from other ECUs and sensors received through the first and second CAN buses 25 and 26, And two CAN driver drive control devices 21 for controlling the driving of the first and second CAN drivers 23 and 24 in response to the output of the first and second CAN drivers 23 and 24. Since two CAN driver drive control devices 21 are provided to control the drive of each of the first and second CAN drivers 23 and 24, a device for controlling the drive of the first CAN driver 23 is provided by a first CAN driver drive control device 21a (FIG. The CAN controller 1 is referred to as a CAN controller 1 in the drawings, and the device that drives and controls the second CAN driver 24 is referred to as a second CAN driver drive controller 21b (referred to as a CAN controller 2 in the drawing).
[0026]
Since the first CAN driver control unit 21a and the second CAN driver control unit 21b have the same configuration, the second CAN driver control unit 21b will be described here as a representative. The second CAN driver drive control device 21b detects a signal TX1 output from the first CAN driver drive control device 21a and input to the first CAN driver 23, and oscillates a pulse signal based on the detected output signal TX1. The signal TX2 input to the second CAN driver is changed from passive to dominant at the timing when the signal TX1 input to the first CAN driver 24 changes potential from passive to dominant and from dominant to passive. And a delay circuit 29 which is a control means for controlling the timing at which the potential changes from dominant to passive to be delayed by a time corresponding to the pulse width of the pulse signal oscillated from the one-shot pulse oscillator 28. When the one-shot pulse oscillator 28 and the delay circuit 29 provided in each of the first and second CAN driver control devices 21a and 21b are individually represented, the first is assigned a suffix a and the second is assigned a suffix b.
[0027]
In the first CAN driver drive control device 21a, the one-shot pulse oscillator 28a detects the signal TX2 output from the second CAN driver drive control device 21b and input to the second CAN driver 24, and based on the signal TX2 which is a detection output. Except for oscillating a pulse signal, the configuration is the same as that of the second CAN driver drive control device 21b. Note that the signal RX1 input from the first CAN driver 23 to the first CAN driver drive control device 21a and the signal RX2 input from the second CAN driver 24 to the second CAN driver drive control device 21b are based on the first and second CAN buses 23, 24. Respectively represent the signals received through.
[0028]
FIG. 2 is a timing chart of signals of various parts in the ECU 22 and signals output from the CAN driver drive control device 21. In this specification, similarly to the case where the high potential state in the CAN buses 25 and 26 is referred to as dominant and the low potential state is referred to as passive, the signals of the various parts in the ECU 22 and the output from the CAN driver drive control device 21 are referred to. Regarding the signal generated, a state where the potential of the signal waveform is high is called dominant, and a state where the potential is low is called passive. Reference numerals designating the units A to C shown in FIG. 2 and in the drawings described later are also used as codes representing signals in the designating units.
[0029]
In response to a rising signal from the dominant of the part A to the passive state input from the CPU 27 to the first CAN driver drive control device 21a, a rising signal from the dominant to the passive part of the part B input to the second CAN driver drive control device 21b from the CPU 27. Is oscillated with a delay for a very short operation time t3 in the CPU 27. Therefore, when the rising signal is input from the CPU 27 to the first CAN driver control device 21a, since the passive signal is input to the second CAN driver control device 21b, the one-shot pulse oscillator 28a , Only passive signals are detected. In a state where the one-shot pulse oscillator 28a detects a passive signal, the one-shot pulse oscillator 28a does not oscillate a pulse and the delay circuit 29b is set not to execute a delay operation. The signal TX1 output from the device 21a to the first CAN driver 23 is the same as the signal in the section A above.
[0030]
On the other hand, in the second CAN driver drive control device 21b, the rising signal is already input to the first CAN driver drive control device 21a before the rising signal is input from the CPU 27 of the section B to the second CAN driver drive control device 21b. Therefore, the one-shot pulse oscillator 28b detects the rising and falling signals of the dominant / passive change in the signal of the portion A input to the first CAN driver drive control device 21a, and oscillates the pulse signal according to the detection result. The delay circuit 29b outputs to the second CAN driver 24 a signal TX2 obtained by delaying the signal input to the portion B by a time corresponding to a preset pulse width of the pulse signal oscillated from the one-shot pulse oscillator 28b. , The second CAN driver 24 is driven.
[0031]
FIG. 3 is a simplified circuit diagram showing the delay circuit 29, and FIG. 4 is a timing chart of signals in various parts of the delay circuit 29. With reference to FIG. 3 and FIG. 4, a driving method of the CAN driver according to the embodiment of the present invention will be described. The delay circuit 29 serving as a control means includes a clock 31, a flip-flop 32, an inverting circuit 33, a first AND circuit 34 (denoted by AND1 in FIG. 3), and a second AND circuit 35 (denoted by AND2 in FIG. 3). ) And an OR circuit 36. Reference numerals designating the units S1 to S5 in the circuit shown in FIG. 3 are also used as codes representing signals at the designated parts.
[0032]
Strictly speaking, the signal B shown in FIG. 4 has a delay time t3 with respect to the signal A shown in FIG. 2, but since the delay time t3 is short, the delay time t3 is ignored on the timing chart. At the same timing as the signal A.
[0033]
In the signal B, the time when the signal rises from the passive state to the dominant is represented by ta, and the time when the signal B falls from the dominant to the passive state is represented by tc. As described above, the one-shot pulse oscillator 28b oscillates the pulse signal C by detecting the rise time ta and the fall time tc of the signal A having the same timing as the signal B. The time t1 corresponding to the pulse width of the pulse signal C is set to a desired value in advance.
[0034]
The flip-flop 32 of the delay circuit 29 responds to the falling times tb (= ta + t1) and td (= tc + t1) of the pulse signal C detected by the clock 31, and the flip-flop 32 operates at times tb and td when the falling is detected. The memory is configured to store the data of the signal B input to the terminal D of the flip-flop 32 and to output the stored data as the signal S1 from the other terminal Q of the flip-flop 32 when the falling is detected. Element.
[0035]
The first AND circuit 34 compares the signal S1 with the pulse signal C, and when both signals coincide with each other in the dominant mode and the passive mode, the two signals become the same signal. If they do not match, the signal S2 is output so as to be passive. The inverting circuit 33 inputs the signal S3 obtained by inverting the dominant and the passive of the pulse signal C to the second AND circuit 35. The operation of the second AND circuit 35 is the same as that of the first AND circuit 34. The second AND circuit 35 compares the signal B with the inverted signal S3. If both signals match, the two signals become the same signal. In this case, the signal S4 is output so as to be passive.
[0036]
The OR circuit 35 compares the signal S2 and the signal S4, and when at least one of the signals is dominant, the signal becomes dominant, and when both signals are both passive, the signal becomes passive. Output S5. Here, the signal S5 is a signal TX2 output from the second CAN driver drive control device 21b to the second CAN driver 24.
[0037]
As described above, the second CAN driver drive control device 21b compares the signal B input from the CPU 27 with the timing of the signal TX1 (= signal A) output from the first CAN driver drive control device 21a to the first CAN driver 23. Thus, the signal TX2 delayed by the time t1 corresponding to the pulse width of the pulse signal oscillated by the one-shot pulse oscillator 28b can be output to the second CAN driver 24.
[0038]
FIG. 5 is a timing chart of potential change formation in the first and second CAN buses 25 and 26 of the CAN communication system 20. FIG. 5 shows that the driving of the first and second CAN drivers 23 and 24 is controlled in response to signals TX1 and TX2 output from the first and second CAN driver driving control devices 21a and 21b, and the first and second CAN buses are controlled. A timing chart of a potential change from passive to dominant and from dominant to passive formed at 25 and 26 is shown.
[0039]
As described above, the timing of the signal TX2 output from the second CAN driver drive control device 21b to the second CAN driver 24 is the timing of the signal TX1 output from the first CAN driver drive control device 21a to the first CAN driver 23. Is delayed by the time t1 corresponding to the pulse width of the pulse signal oscillated from the one-shot pulse oscillator 28b. With this, with respect to the potential change from passive to dominant and dominant to passive formed on the first CAN bus 25, the timing of the potential change from passive to dominant and dominant to passive formed on the second CAN bus 26 can be changed. The above-described time t1 can be shifted.
[0040]
FIG. 6 is a timing chart of signals in a CAN communication system including three CAN drivers and three CAN buses. With reference to FIG. 6, a driving method of a CAN driver according to another embodiment of the present invention will be described.
[0041]
In FIG. 6, in a CAN communication system including three CAN drivers and three CAN buses (not shown), signals input from the first to third CAN driver driving devices to the first to third CAN drivers, respectively, 7 shows a timing chart with pulse signals respectively oscillated from one-shot pulse oscillators (shown as pulse oscillators 2 and 3 in FIG. 6) provided in the third and third CAN driver driving devices.
[0042]
It should be noted here that the pulse width: time t2 of the pulse signal oscillated by the one-shot pulse oscillator provided in the third CAN driver drive controller is equal to the pulse width of the pulse signal oscillated by the one-shot pulse oscillator provided in the second CAN driver drive controller. Pulse width: is set to be longer than time t1 (t2> t1).
[0043]
As described above, the pulse width of the pulse signal oscillated by the one-shot pulse oscillator provided in the second and third CAN driver drive control devices is determined by the second CAN driver and the third CAN driver connected to the second and third CAN driver drive control devices, respectively. , The timing of the dominant / passive change of the signal input to the second CAN driver is shifted from the timing of the dominant / passive change of the signal input to the first CAN driver, and the third CAN The time when the timing of the dominant / passive change of the signal input to the driver is shifted can be made different. That is, the timing of the dominant / passive change of the signals input to the three first to third CAN drivers can be shifted from each other so as not to be superimposed.
[0044]
As described above, in the embodiment of the present invention, the device including the intelligent terminal constituting the CAN communication system is an electronic control unit (ECU), but is not limited thereto, and may be used in various other industrial devices. There may be.
[0045]
【The invention's effect】
According to the present invention, in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses, a signal input to one CAN driver selected from the plurality of CAN drivers is used. The CAN driver shifts the timing of the change from passive to dominant and from dominant to passive and the timing of the signal input to the remaining CAN drivers except one CAN driver changing from passive to dominant and dominant to passive. Driven. Thus, it is possible to prevent the timing of the potential change formed on the CAN bus connected to each of the plurality of CAN drivers from being superimposed. Therefore, it is possible to prevent the noise current generated at the time of the potential change in each CAN bus from being added to affect the CAN communication system, and to limit the influence of the noise current generated at the time of the potential change in each CAN bus. Therefore, it is possible to reduce the adverse effect of the noise current.
[0046]
Further, according to the present invention, the timing at which a signal input to one CAN driver selected from a plurality of CAN drivers changes from passive to dominant and from dominant to passive, and the remaining CAN drivers excluding one CAN driver The difference between the timing at which the signal input to the device changes from passive to dominant and from dominant to passive is the time corresponding to the pulse width of the pulse signal oscillated based on the detection output of the signal input to one CAN driver. This is realized by delaying the signals input to the remaining CAN drivers except one CAN driver. As described above, the timing of the potential change formed on the CAN bus connected to each of the plurality of CAN drivers by a simple method of using the pulse signal oscillated based on the detection output of the signal input to the CAN driver. Can be prevented and the adverse effect of the noise current can be reduced.
[0047]
Further, according to the present invention, when at least three or more CAN drivers are provided, the pulse width of the pulse signal is determined based on the pulse signal so that the timing at which the input signal changes from passive to dominant and from dominant to passive is determined. It is set differently for each driver. In this way, the timing of the potential change of the CAN bus connected to the remaining two or more CAN drivers does not overlap with the timing of the potential change of the CAN bus connected to the one CAN driver. Further, by a simple method of setting the pulse width of the pulse signal to be different for each CAN driver, it is possible to easily prevent the timing of the potential change in the plurality of CAN buses from being superimposed.
[0048]
According to the present invention, in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses, a CAN connected to one CAN driver selected from the plurality of CAN drivers. Controlling the driving of the CAN driver so that the timing of the potential change formed on the bus and the timing of the potential change formed on the CAN bus connected to the remaining CAN drivers except one CAN driver are shifted. A CAN driver drive control device that can be realized. In a CAN communication system including such a CAN driver drive control device, overlapping of timings of potential changes formed on the CAN bus connected to each of the plurality of CAN drivers is prevented, and adverse effects of noise current are reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a simplified configuration of a CAN communication system 20 including a CAN driver drive control device 21 according to an embodiment of the present invention.
FIG. 2 is a timing chart of signals of various parts in an ECU 22 and signals output from a CAN driver drive control device 21.
FIG. 3 is a circuit diagram schematically showing a delay circuit 29;
FIG. 4 is a timing chart of signals in each section of the delay circuit 29.
FIG. 5 is a timing chart of potential change formation in first and second CAN buses 25 and 26 of the CAN communication system 20.
FIG. 6 is a timing chart of signals in a CAN communication system including three CAN drivers and three CAN buses.
FIG. 7 is a system diagram showing a simplified configuration of a conventional CAN communication system 1.
FIG. 8 is a timing chart relating to passive and dominant formation in first and second CAN buses 3 and 4;
[Explanation of symbols]
20 CAN communication system
21 CAN driver drive control device
22 ECU
23 1st CAN driver
24 Second CAN driver
25 1st CAN bus
26 Second CAN Bus
27 CPU
28 One-shot pulse oscillator
29 Delay circuit

Claims (4)

A method for driving a CAN driver in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses,
A signal input to one CAN driver selected from the plurality of CAN drivers is detected, and a signal input to the one CAN driver changes from passive to dominant and from dominant to passive based on a detection output. The CAN driver is configured to drive the CAN driver so as to shift the timing at which the signal input to the CAN driver other than the one CAN driver changes from passive to dominant and from dominant to passive. Drive method. Oscillating a pulse signal based on a detection output of a signal input to the one CAN driver,
With respect to the timing when the signal input to the one CAN driver changes from passive to dominant and from dominant to passive, the signal input to the remaining CAN driver except for the one CAN driver is changed from passive to dominant and from dominant to passive. 2. The method of driving a CAN driver according to claim 1, wherein the timing of changing to (1) is shifted by delaying by a time corresponding to the pulse width of the pulse signal. When at least three or more CAN drivers are provided,
The pulse width of the pulse signal is
3. The driving of the CAN driver according to claim 2, wherein the input signal is set to be different for each of the CAN drivers for which the timing at which the input signal changes from passive to dominant and from dominant to passive is determined based on the pulse signal. Method. A drive control device for a CAN driver in a CAN communication system that performs communication via a plurality of CAN drivers respectively connected to a plurality of CAN buses,
Pulse oscillating means for detecting a signal input to one CAN driver selected from the plurality of CAN drivers and oscillating a pulse signal based on the detected output;
The timing at which the signal input to the one CAN driver changes from passive to dominant and from dominant to passive changes the timing at which the signal input to the own device changes from passive to dominant and from dominant to passive. Control means for controlling so as to delay by a time corresponding to the pulse width of the CAN driver.

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