JPH0548618A - Multiplex transmission equipment - Google Patents

Abstract

PURPOSE:To obtain a multiplex transmission equipment by which the maximum value of a message latent time is decided designingly in a nondestructive arbitration type line contention system multiplex transmission system. CONSTITUTION:The transmission equipment is provided with a storage circuit 16 storing the priority corresponding part of a message whose priority in storing in a current multiplex transmission line is higher when a specific transmission node is failed in the line contention and the priority of its own message is dynamically revised to be higher priority by referencing to the stored priority. Moreover, the priority part and the destination designation part of the message are stored to separate locations of the message. Since the transmission time of the message is confirmed in such a manner, the application of the transmitter to a coordinate controller for automobiles is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-destructive arbitration type contention system multiplex transmission device, and more particularly to a multiplex transmission device suitable for data communication between vehicle controllers.

[0002]

2. Description of the Related Art In recent years, various electronic control devices used in vehicles have been remarkably developed. Especially, in automobiles, microcomputers are used for various controls such as engines, transmissions, brakes, constant-speed traveling devices, and traction control devices. It can be said that the electronic control device using is used and the performance thereof has almost reached the saturated state.

Therefore, in order to further improve the function, the idea of total control is created, in which the respective control devices are not operated individually but are combined with each other to operate cooperatively, and in the future. Is in the moment that will surely be realized. For example, in an electronically controlled automatic transmission (called an electronic A / T), it is considered to operate cooperatively with an electronic engine control device. There is. That is, in synchronization with the process of changing the gear ratio of the automatic transmission, the engine control device appropriately controls the torque generated at that moment to reduce the shock at the time of change to improve the riding comfort and the transmission. By suppressing the upper limit of the stress applied to the vehicle, it is possible to reduce the weight of the vehicle transmission itself.

For this purpose, the predetermined data calculated by the main control device of the cooperative control must be accurately and accurately transmitted to the subordinate individual devices at the right time, and the expandability is high. In order to do so, this master-slave relationship is not fixed, and it is necessary to realize so-called bidirectional, masterless mutual data transfer, in which another device can take the position of master in some cases.

Therefore, for such a request, for example, in Japanese Patent Laid-Open No. 61-195453, prioritization is performed by adding an identifier according to the urgency or importance of the message to be transmitted. In order to prevent the degradation of the line efficiency, the CSMA / CD (Carrier Se
nse Multiple Access with Collision Detection) has been proposed as a so-called non-destructive arbitration type contention-based multiplex transmission method.

Incidentally, as a device related to this kind of device, there are JP-A-55-147853 and JP-A-57-8.
No. 7685, JP-A-60-24747, and JP-A-2-126742 can be mentioned.

[0007]

The above-mentioned prior art is characterized in that the transfer delay time of data from a certain transmitting node to a certain receiving node (this is latency time Latency T
ime, which is an important performance measure of the CSMA / CD method, is not given definitely, but the priority of the corresponding message and the priority of other messages already sent on the transmission line. No consideration has been given to the fact that it is given only statistically from the rank and the line occupancy rate, and when applied to the above-mentioned comprehensive control of vehicles such as automobiles, there is a problem that control timing is broken.

That is, the latency is not limited to a definite upper and lower limit value, but is given only by a probabilistic guideline. Therefore, in a situation where a certain control device should perform cooperative control, If the command was sent to another control device, but accidentally another control device was sending a high-priority message, the command would be kept waiting for a long time, and the control timing would be broken. Will cause

On the other hand, in order to definitely obtain this latency,
After repeating the experiment many times, it was almost impossible to reproduce the same line condition, and the latency could not be determined. In addition, such uncertainties of control and poor reproducibility can be a great bottleneck in design and experiment in the comprehensive control of automobiles in which real-time property is important and strict delay time is a problem.

An object of the present invention is to solve the above problems and provide a non-destructive arbitration-type contention-type multiplex transmission device capable of arbitrarily setting the maximum value of the transfer delay time.

[0011]

In order to achieve the above object, according to the present invention, when a certain transmitting / receiving node fails to contend for a line, the priority code in the transmission message of another node already occupying the line is set. A means for storing and holding, and a means for transmitting a message having a higher priority than the message currently monopolizing the line from its own node,
It is provided to at least one station of the transmitting / receiving node.

According to another aspect of the present invention, an accommodating portion of the priority code in a transmission message sent from a transmitting / receiving node and an accommodating portion of an address used for designating a destination of a receiving node that should receive the message. Occupy different places in the message.

[0013]

The means of the present invention is a nondestructive arbitration type CS.
In a MA / CD multiplex transmission system, when a node fails to contend for a line at the time of transmission, it stores and retains the priority code of the message of another node that has contended on the line and has acquired the transmission right. , Has a higher priority than the message of its own node), and works to forcibly eliminate the situation if the contention for the line continues to fail.

Here, the situation where the contention for the line continues to fail is generally measured by a certain time timer,
The maximum value of the timer is
A design value that does not break the real-time controllability is selected (so-called timeout method).

When such a situation occurs in a particular node, a message having a higher priority than that is temporarily sent out, thereby exerting an effect of preventing the hang-up of the multiplex transmission line.

The message whose priority has been temporarily increased may be a normal message which has continued to fail in contention at the node, or a system for all node devices connected to the multiplex transmission path. It may be control information such as a so-called warning signal that has a meaningful meaning.

Next, the other means according to the present invention solves the increase in the bit width of the priority code (that is, the decrease in the message efficiency in the whole message frame) when the priority of the message is variable. Work like.

That is, when a plurality of priority codes are allowed to be used for one message as in the present invention, the information amount of the priority code itself is lowered. For example, in the prior art of Japanese Patent Laid-Open No. 61-195453, the priority code is also used as the address information of the message (destination, content, or identification information such as an event command). However, when the present invention is applied to such a system, a plurality of priority codes are associated with the same address information, so that the bit width of the priority code is inevitably increased. Moreover, since the code itself is used for bit-synchronized line arbitration (called bit-wise arbitration), strict bit-synchronization is required, thus increasing such duration on the message frame. As a result, there is a drawback that the responsiveness and reliability of the entire system are lowered.

However, according to the present invention, the priority portion in which the bit arbitration is performed and the address information are separated, the width of the line arbitration period of the bit synchronization is reduced equivalently, and these are based on the increase of the arbitration width. The drawbacks of can be eliminated.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A multiplex transmission device according to the present invention
This will be described in detail with reference to the illustrated embodiment. FIG. 1 shows an embodiment of the present invention, showing one of the transmitting and receiving nodes of a plurality of stations when the present invention is applied to a vehicle multiplex transmission apparatus. In the figure, 1 is a CSMA / CD. System communication control circuit, which is a discrete element or dedicated LS
At least one is provided in the control unit mounted on each part of the vehicle, and is connected to the control MPU 3 of the control unit via the bus 2 for data exchange, On the other hand, it is connected via a physical layer interface 4 to a multiplex transmission line 5 which connects each control unit transversely.

The physical layer interface 4 is shown in FIG.
Which has an internal circuit configuration as shown in FIG. 2 and has a function with respect to the multiplex transmission line 5 is a transmission data transmission function having an overwrite capability by the dominant bit of the inferior bit,
It is a data receiving function having a waveform shaping capability by the comparator 18.

In this embodiment, the multiplex transmission line 5 is shown as an unbalanced single line, but a balanced two-wire transmission line (twisted pair) or optical transmission line (optical Fiber) or the like may be used. Then, in this case, this physical layer interface 4
Also, you have to change to a circuit that suits it,
The basic function is as described above.

In the multiplex transmission line 5 shown in FIG. 2, 4a representing physical layer interfaces of two transmitting / receiving nodes of different stations.
And 4b are connected. Then, when the combination of the signal values given to the transmission signal terminals Tx1 and Tx2 of these nodes at the same time is changed, what values the reception signal terminals Rx1 and Rx2 of each node take will be described with reference to FIG. Is specified in.

Here, the logic "1" is the dominant signal and corresponds to the positive voltage in FIG. 2 (voltage on the V + side shown in FIG. 2), while the logic "0" is the dominant signal and is shown in FIG. It corresponds to the ground voltage at.

As is apparent from FIG. 3, a logical "0"
The transmission signal of 1 is overwritten by the transmission signal of logic "1", and the reception signal at this time becomes logic "1". This is the reason for distinguishing signals from inferiority and superiority, and is a basic principle for realizing nondestructive arbitration of bit synchronization.

Next, in this CSMA / CD multiplex transmission system, it is shown in FIG. 1 how the data exchanged by the MPU 3 is exchanged with the multiplex transmission line 5.
Will be explained.

Data to be transmitted by the MPU 3 is sent to the transmission buffer 6 of the communication control circuit 1 through the bus 2. When the control circuit 8 detects an empty state of the multiplex transmission path 5 (continuation of the inferiority signal for a predetermined period), the data is sent from the transmission buffer 6 to the transmission shift register 7, is parallel-serial converted, and is then transmitted. It

On the other hand, during this transmission period, the bit comparator 9 in the communication control circuit 1 detects the difference between the signal level transmitted by its own node and the signal level appearing on the multiplex transmission line 5. Then, if the signal level transmitted by the own node and the signal level of the multiplex transmission line 5 are different,
This is evidence that multiple transmission nodes started transmission at the same time, and that the self node lost the transmission right.

Therefore, at this time, the arbitration circuit 10 immediately interrupts the transmission, displays on the control register 11 that the contention for the line has been lost, and operates so as to immediately change the transmission / reception node to the operation as the reception node. To do.

When a plurality of transmission / reception nodes start transmission at the same time, these signals determine the signal value on the multiplex transmission line 5 according to the principle of superposition of the above-mentioned superior and inferior signals. Signal superposition is usually
It is done in the area of the priority code located at the beginning of the message, and the one with the more dominant bits towards the beginning of the message finally gets the right to send.

The state of the bitwise arbitration is shown in detail in FIG. 4, and here, the case is shown in which the transmission / reception nodes 1 to 3 start transmission at the same time. The message of the transmission / reception node 1 survives, and this message is nondestructively transmitted on the multiplex transmission line 5 without the interference of the transmission / reception nodes 2 and 3.

Returning to FIG. 1 again, the transmission / reception node that has lost the contention for a line immediately becomes the reception node, the bit synchronization is continued by the function of the synchronization circuit 12, and the remaining signals are taken into the reception shift register 13. Then, when the reception of the data for one frame is completed, the address information at the specific position of the received data is compared by the destination comparator 14, and if the message is for the own node, the control circuit 8 serializes the data. It is converted into parallel data and then stored in the reception buffer 15. Therefore, here, the MPU 3 can refer to the data addressed to the own node via the bus 2. On the other hand, at this time, data that is not the data for the own node is normally discarded.

In FIG. 1, reference numeral 16 is a memory circuit for storing and holding the priority code appearing on the multiplex transmission line when the own node fails in the contention for the line. If the contention of the other node fails, it retains the priority code part of the message of the last surviving other node. And this memory circuit 1
The operation of 6 is always executed when the transmission fails, regardless of whether the message is addressed to the own node.

The contents of this latch A17 are
Can be referred to by the MPU 3 via this, and thereby the MPU 3 dynamically executes a process of changing the priority of its own node message.

However, like another embodiment described later,
The communication control circuit 1 itself may refer to the contents of the latch A17 to dynamically change the priority code of the message, or may issue a control command different from the transmission data and having a higher priority. You may make it transmit. It should be noted that such a function is automatically performed by the sequence stored in the control circuit 8 without intervention of the MPU 3.

Next, the operation of this embodiment will be described with reference to the flow chart of FIG. In addition, in this embodiment, in FIG.
The MPU 3 shown in FIG. 5 executes a series of procedures according to the flow of FIG.

First, in step 20, the MPU 3 reads data from the control register 11 in the communication control circuit 1 to determine whether or not the contention for the line has failed. If the contention fails, the process proceeds to step 21 to determine whether the message has not been transmitted for a certain period or longer. Here, whether or not it is within a certain period is normally determined by using the timer function of the MPU 3, and a predetermined design value is selected for the length of this period so as not to impair the real-time property of the comprehensive control. Then, if the transmission is not performed for the predetermined period, the process proceeds to step 22 and step 23.

First, in step 22, the priority code of the message currently occupying the line is acquired from the latch A17 in the memory circuit 16. Then, in step 23, the message is retransmitted using the priority order as a reference and a temporary priority order higher than that and assigned to the own node in advance. And step 2
In step 4, by the same means as in step 20, it is confirmed whether or not the transmission has actually succeeded with the temporarily increased priority, and if the transmission has failed again, the operations of step 22 and step 23 are performed. repeat. Then, if the transmission is successful here, the priority of the message is returned to the normal priority in step 25, and the process is terminated.

In the above description, the MPU 3 executes the algorithm shown in FIG. 5, but as another possible embodiment, the communication control circuit 1 itself can execute this algorithm without the instruction of the MPU 3. It may be configured to execute. In the case of this embodiment, the above algorithm will be stored in the control circuit 8.

However, even in this case, the latch A1
7 must exist as an internal mechanism, and the MPU 3 may take a form that cannot be referred to, as in the above embodiment.

By the way, up to now, the method of how the node, which has continuously failed to contend for the line, acquires the transmission right has been described. However, in this embodiment, the following convenience can be given to the operation of the node that has continued to occupy the line.

As is apparent from the above description, in this embodiment, the node that has occupied the line fails to continuously acquire the transmission right at some point. Then, at this time,
The latch A17 (shown in FIG. 1) of that node should store the temporary high priority code assigned to another node.

Therefore, if the node occupying this line recognizes that this code is an interrupt signal corresponding to a hang-up warning of the line, then the node in question is a node for other nodes, It has been found that the utilization rate of the line must be reduced, and therefore, at this time, the relevant node can appropriately operate the traffic on the transmission line by delaying the transmission time interval.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 6 shows the structure of the message frame as shown in the figure. The part represented by the priority bit in the figure is used for the bit-wise arbitration described in the above embodiment. As mentioned above, it is a part that is changed according to the situation of the line.

Next, the portion following the priority bit, which is represented by the destination bit in the figure, represents the address information of the message, and this portion is used for bitwise arbitration. Absent.

Therefore, according to this embodiment, since the priority portion where the bit arbitration is performed and the address information are separated, the arbitration of the line can be decided early and the reliability of the system can be improved. .. Further, this destination bit is the identification information referred to by the destination comparator 14 in FIG. 1. In this embodiment, this destination bit can be determined independently of the priority assignment of the node, so that the system design is flexible. The sex can be increased.

[0047]

According to the present invention, from a certain transmitting node,
The maximum value of the message transfer delay time to a certain receiving node, so-called latency, can be given not only as a stochastic value as in the prior art but as a deterministic value set arbitrarily, As a result, it can be used with confidence in applications such as cooperative control of vehicle parts that require strict real-time performance.

Further, according to the present invention, since the line monitoring function can be strengthened for each of the transmitting and receiving nodes and mutual monitoring capability can be provided, there is an effect that the reliability of the entire system is improved.

Further, according to the present invention, since the priority part and the destination information part on the message frame are separated, the allocation of the priority among the nodes shows what kind of message variations each node has. Since it can be decided independently without depending on, there is also an effect of increasing flexibility in system design.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a multiplex transmission apparatus according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a physical layer interface according to the present invention.

FIG. 3 is an explanatory diagram showing a signal state of a transmission / reception terminal according to an embodiment of the present invention.

FIG. 4 is a timing chart for explaining nondestructive arbitration of bit synchronization in a multiplex transmission system to which the present invention is applied.

FIG. 5 is a flow chart for explaining the operation of the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a structure of a message frame in the embodiment of the present invention.

[Explanation of symbols]

 1 Communication Control Circuit 2 Bus 3 MPU 4 Physical Layer Interface 5 Multiplex Transmission Line 16 Storage Circuit 17 Priority Code Latch A

Claims (2)

[Claims] 1. A multi-transmission line in which a signal state on a transmission line takes two states, a dominant state and a poor state, and transmission / reception nodes of a plurality of stations commonly connected to this multi-transmission line. When communication is performed by the start-stop synchronization method, and the transmission / reception node transmitting the superior signal and the transmission / reception node transmitting the inferior signal exist at the same time, the superior signal becomes the signal state of the multiple transmission line. On the other hand, the priority of the message transmitted from each transmitting / receiving node is coded and given in the message with the combination of the superior pattern and the inferior pattern, and when contention of the multiple transmission line by the plural transmitting / receiving nodes occurs. ,
In a non-destructive arbitration-type contention-type multiplex transmission device in which only a transmitting / receiving node that can faithfully reproduce the priority code according to the superior and inferior patterns on a multiplex transmission line and continues transmission, Storage means for storing and holding the priority code appearing in the multiplex transmission line when the contention fails, and the priority of the message to be transmitted from the own node based on the priority code stored and held in this storage means. A multiplex transmission apparatus, characterized in that priority code control means for dynamically changing is provided in at least one of the transmitting and receiving nodes of the plurality of stations. 2. The invention according to claim 1, wherein an accommodation part of the priority code in a transmission message sent from the transmission / reception node and an address used for designating a destination of a reception node which should receive the message. A multiplex transmission device, characterized in that the part and the part occupy different places in the message.