JP3161156B2 - Multiplex communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex communication system, and more particularly to a multiplex communication system in which a plurality of communication nodes are connected by a common transmission line and two-way multiplex communication is performed between the plurality of communication nodes according to a preset protocol. .

[0002]

2. Description of the Related Art Conventionally, CSMA / C has been used as a method of performing multiplex communication by connecting a plurality of communication nodes via a common transmission line.
D (Carrier Sense Multiple Access / Collision Dete
ction) method is known.

In the CSMA / CD system, in multiplex communication in which a plurality of communication nodes transmit and receive data via a common transmission line, each communication node assigns a priority after waiting for the common transmission line to become free. Data is transmitted, and when data is transmitted from multiple communication nodes at the same time, transmission of high-priority data is prioritized, and other communication is performed after waiting for the common transmission path to become available again. is there.

[0004] According to this method, high-priority data, that is, data important for executing predetermined processing in each communication node, is preferentially output on the common transmission path, and data collision is a problem. In a region where the traffic does not occur, that is, in a region where the traffic is relatively low, high control accuracy can be realized in the multiplex communication system.

However, in a system adopting the CSMA / CD system, when a large amount of data is output to a common transmission path, the frequency of collision with data output from another communication node increases. In this case, data having a low set priority cannot be easily transmitted due to data collision, and a situation occurs in which the data is transmitted with a long delay from the original transmission timing.

In this sense, the CSMA / CD system is suitable for a system with a low communication frequency.
It is mainly used as a multiplex communication method in a region where the communication amount is relatively small compared to the related art.

On the other hand, a token bus system is known as a communication system suitable for a system in which data communication frequency is relatively high. The token bus method is a method in which a communication order is set in advance for each communication node, and each communication node sequentially transmits data on a common transmission path.

According to this method, even if important data is calculated in any one of the communication nodes, the data cannot be transmitted until the order of the communication node comes. Is high, it is possible to reliably transmit all data without a large time delay.

As described above, the lengths of the CSMA / CD system and the token bus system are reversed, and it is examined which system is suitable in accordance with the communication frequency required for the multiplex communication system, and the system is appropriately determined. It was common to be selectively employed.

In a multiplex communication system,
The communication frequency may not be constant. In such a device, if any of the above-mentioned CSMA / CD system or token bus system is adopted as the communication system, the efficiency will be reduced in an area where each system is weak.

In this case, if these communication systems can be appropriately switched according to the amount of data transmitted on the common transmission line, the advantages of both can be enjoyed together, and the control accuracy in the multiplex communication system can be improved. It is possible to plan.

Japanese Patent Laid-Open Publication No. Sho 60-189342 discloses a multiplex communication system focusing on this point. In this multiplex communication system, each of the communication nodes uses a CSMA / CD-based data communication device, a token bus-based data communication device, or any of these communication devices in accordance with the communication frequency of data output to a common transmission path. And a device for switching the operation.

According to this configuration, when the communication frequency of data output to the common transmission line is relatively low, CSMA /
When important data is communicated with priority by the CD method, and when the frequency of data communication is high, data is transmitted from all nodes sequentially and reliably, and appropriate data communication is always performed. become.

[0014]

However, in the above-mentioned conventional multiplex communication system, each communication node is connected by a set of common transmission lines, and the CSMA / CD is appropriately placed on the common transmission line.
This is a configuration in which data based on a transmission frame according to the scheme and data based on a transmission frame according to the token bus scheme are output.

Therefore, each communication node has a CSM
If the common transmission path is disconnected despite having a data processing mechanism according to the A / CD method and a data processing mechanism according to the token bus method, data communication is performed by either communication method. It was impossible to continue.

Further, the above-mentioned conventional multiplex communication system requires a communication system switching mechanism for each communication node, and it is necessary to synchronize the communication system switching timing by these mechanisms with extremely high accuracy. The configuration was not always easily realizable.

Therefore, a system for solving such inconveniences
As shown in FIG. 1, the token bus method
While sending data in the set order,
Token bus communication that receives and exchanges data
Transmission is performed by the communication means T _{1 to} T _n and the CSMA / CD method.
Prioritize data that conflicts with higher-priority data.
In the event of a collision, the transmission of the data is stopped and data collision occurs
Data transmission while receiving necessary data
A CSMA / CD communication means C ₁ -C _n for performing the talk
Nbasu communication means T ₁ through T _n and the CSMA / CD communication hand
Perform a predetermined process based on the data stage C ₁ -C _n is received
And the token bus communication means T _{1 to} T _n and the C
The same data to SMA / CD communication means C ₁ -C _n
Each having data processing means D _{1 to} D _{n for} supplying
Communication nodes N _{1 to} N _n and the plurality of communication nodes N
DOO connecting between the token bus communication unit T ₁ through T _n of ₁ to N _n
A common transmission path L _T for Kunbasu, the communication node N ₁ of said plurality of
Connecting between the CSMA / CD communication means C ₁ -C _n of to N _n
Multiplexing communication with CSMA / CD common transmission line L _C
A system is conceivable. In such a configuration, the talk
Common transmission line L _T or CSMA / CD for the common heat transfer for Nbasu
Even if one of the transmission lines L _C is disconnected, the other common transmission line is connected.
Communication can be continued via the data processing means D
_{1 to} D _n are token bus communication means T _{1 to} T _n and CSMA /
Based on data received by both CD communication means C ₁ -C _n
Token bus method and CS
A mechanism for switching between the MA / CD system is not required.
Therefore, according to the above configuration, the common transmission between the communication nodes is performed.
To realize fail-safe when the line is disconnected
In both cases, the need for communication system switching is eliminated,
The described inconvenience can be solved. by the way,
In the above multiplex communication system, the token bus system
Timing of data transmission by CSMA / CD and data transmission by CSMA / CD system
Communication node malfunctions due to delay in data transmission
May move. Therefore, the token bus method
Transmitted data and transmitted by CSMA / CD system
Only when the data is the same,
The communication node executes predetermined processing based on the
For example, it is possible to prevent a malfunction of the communication node.
However, in such a hand method, the token bus system
Data transmitted by the CSMA / CD system
Data must be the same as the
The responsiveness of the processing in the node will deteriorate. The present invention
Are made in view of the above points, and each communication node
To prevent malfunctions and improve process responsiveness
To provide a multiplex communication system capable of achieving
Aim.

[0018]

The object of the present invention is to provide a token
The bus method transfers data in a preset order.
While sending, receiving necessary data and sending and receiving data
Token bus communication means T _{1 to} T _n and CSMA / CD
Prioritize outgoing data by method, giving higher priority
When collision with high-level data occurs, the transmission of the data is stopped.
To avoid data collisions while receiving required data.
CSMA / CD communication means C ₁ for transmitting and receiving data
To C _n , the token bus communication means T _{1 to} T _n and the
Based on the data received by the CSMA / CD communication means C _{1 to} C _n
And performs a predetermined process on the token bus communication operator.
The stage T ₁ through T _n and the CSMA / CD communication means C ₁ -C _n
Data processing means D _{1 to} D _n for supplying the same data to
When a plurality of communication nodes N ₁ to N _n included in each,
The token bus communicators of the plurality of communication nodes N _{1 to} N _n
A token bus common transmission line L _T connecting the stages T _{1 to} T _n ;
The CSMA / CD communication of the plurality of communication nodes N _{1 to} N _n
CSMA / CD common transmission line L _C connecting means C _{1 to} C _n
In the multiplex communication system comprising:
The management unit D ₁ to D _n is the data to execute the predetermined processing
After taking in, the token bus communication means T _{1 to} T _n and the
The data received by the CSMA / CD communication means C _{1 to} C _n
Because became identical, the token bus communication unit T ₁ ~
T _n receiving the same data continuously, and
CSMA / CD communication means C ₁ -C _n is the same data is continuously
To detect the earliest event that has occurred
An event detection unit, wherein the data processing units D _{1 to} D _n include:
The data constituting the event detected by the event detection means
This is achieved by a multiplex communication system that executes the predetermined processing based on data.

[0019]

[0020]

[0021]

[Action] In the multiplex communication system according to the present invention, the communication node N ₁ to N _n are connected to one another via a common transmission path L _C for common transmission path L _T and the CSMA / CD for the token bus. Then, each of the communication nodes N _{1 to} N _n
Between them, the token bus communication means T _{1 to} T _n and the CSMA / CD communication means C _{1 to} C _n exchange data separately and independently.

Therefore, the token bus common transmission line L
If one of _T or the CSMA / CD for common transmission path L _C is broken, the communication through the other common transmission line can be continued.

The data processing means D₁~ D_nIs
The token bus communication means T₁~ T _nAnd the CSMA
/ CD communication means C₁~ C_nBased on the data received by both
Token bus method
No mechanism is required to switch between CSMA / CD format.
No.

[0024]

[0025]

The event detecting means may determine whether the data received by the token bus communication means T _{1 to} T _n and the data received by the CSMA / CD communication means C _{1 to} C _n are the same. T _{1 to} T _n or the above CSMA / C
It is detected that the same data is continuously received by the D communication means C _{1 to} C _n .

[0027] Here, the token of the communication node N ₁ to N _n bus communication unit T ₁ through T _n and the CSMA / CD
When the communication means C _{1 to} C _n receive the same data, the data is guaranteed to be accurate as described above, and the data processing means D _{1 to} D _n process the data. Should be the basis.

On the other hand, CSMA / CD communication means C ₁ -C _n
Receive the same data successively when the data has a high priority and is transmitted a plurality of times in the CSMA / CD system during the waiting by the token bus system.

The reason why the token bus communication means T _{1 to} T _n continuously receive the same data is that the CSMA / CD
This is a case where data to be transmitted by the method is greatly delayed due to data collision on the common transmission path, and a case where the disadvantage of the CSMA / CD method becomes apparent.

That is, when any one of the events is detected by the event detecting means, the data constituting the event is important for controlling the multiplex communication system, and the data is stored in each of the communication nodes N _{1 to} N _n . The data is to be received by the processing means D _{1 to} D _n and subjected to predetermined processing.

If such data is processed in the data processing means D _{1 to} D _n , the token bus communication means T _{1 to} T _n and the token bus communication means T _{1 to} T _n may be processed due to the difference in each communication system. CSMA / CD communication means C ₁
-C _n is, in the case of receiving with a time difference of the same data is also in the data processing unit D ₁ to D _n in the appropriate precision, and will be treated with the appropriate response speed is executed.

[0032]

FIG. 2 is a block diagram showing the configuration of a communication node 10 constituting a multiplex communication system according to an embodiment of the present invention.

As shown in FIG. 1, a communication node 10 includes a random access memory (RAM) 13 and a read-only memory (ROM) connected to each other via a common bus 12 around a central processing unit (CPU) 11. 14, an input / output port 15, a token bus communication circuit 16 connected to the input / output port 15, and a CSMA / CD communication circuit 17.

The token bus communication circuit 16 is connected to a common transmission line 18 for token bus, and the CSMA / CD communication circuit 17 is connected to a common transmission line 19 for CSMA / CD.

In the apparatus of this embodiment, the token bus communication circuit 16 is provided with
The SMA / CD communication circuit 17 is connected to the above-mentioned CSMA / CD communication means, and is connected to the CPU 11, the common bus 12, the RAM 1
3. The ROM 14 corresponds to the data processing means described above.

Here, the multiplex communication system of this embodiment is
The communication node 10 includes a plurality of other communication nodes having substantially the same hardware configuration, the token bus common transmission line 18, and the CSMA / CD common transmission line 19. The token bus common transmission line 18 connects between the token bus communication circuits of each communication node, and the CSMA / CD common transmission line 19 connects between the CSMA / CD communication circuits of each communication node.

Hereinafter, referring to FIG. 3, a token bus system and a CSMA system adopted as a communication system of the apparatus of this embodiment will be described.
Token bus communication circuit 1 for exchanging data between communication node 10 and another communication node by the / CD method
6 and the operation of the CSMA / CD communication circuit 17 will be described.

Here, the token bus system is a system in which each communication node sequentially transmits data on a common transmission line according to a predetermined communication order. The data frame shown in FIG. 3A is an example of a data frame transmitted and received by the token bus communication circuit 16 for realizing communication in accordance with such rules.

That is, when transmitting data by the token bus method, a communication node that transmits data transmits its transmission order together with the transmission destination address of the data prior to the data.

The other communication node determines whether or not to take in data depending on whether or not the destination address output on the token bus common transmission line 18 specifies itself, and determines whether or not to take in the data. It is to judge whether or not the own transmission order has been turned based on the transmission order output on 18.

According to this method, data is not transmitted from a plurality of communication nodes at the same time, and the data is reliably transmitted between the plurality of communication nodes constituting the multiplex communication system via the common transmission path 18 for the token bus. Will be given and received.

On the other hand, the CSMA / CD system means that when a data transmission request is generated at each communication node, data is transmitted as appropriate while waiting for a common transmission path to become free. This is a communication method that prioritizes transmission of high-frequency data.

FIG. 3B shows an example of a data frame exchanged by the CSMA / CD communication circuit 17 of the communication node 10 in order to realize communication in accordance with such rules. That is, when transmitting data, the CSMA / CD communication circuit 17 in the apparatus of the present embodiment transmits a priority and a destination address set based on the importance of data before transmitting the data.

That is, the communication node that has issued the transmission request is
It is checked whether or not the CSMA / CD common transmission line 19 is occupied by data generated by another communication node. If the common transmission line 19 is vacant, the priority is output prior to the data and the self transmission is performed. It monitors whether another priority signal is superimposed on the priority signal. Then, data transmission is performed only when the own priority signal survives, and when a higher priority signal is superimposed,
In this configuration, transmission is immediately stopped.

Whether or not the priority has survived is determined, for example, by forming a priority signal of a predetermined bit by “1” and “0”, and the signal generated by itself is present on the common transmission line as it is. It is possible to easily judge by seeing whether or not it is performed.

According to such a system, when a transmission request for important data having high priority occurs in a plurality of communication nodes constituting a multiplex communication system, the transmission can be immediately executed.

Here, comparing the above token bus system and this CSMA / CD system, the token bus system ensures that data is transmitted from all communication nodes, but has a different priority from the CSMA / CD system. However, there is a disadvantage that even if the data has high data, the data is not transmitted until the transmission order of the communication node comes.

On the other hand, the CSMA / CD system has an advantage that data having a high priority can be transmitted immediately as described above, but when the frequency of data communication on the common transmission line 19 is high, the priority is low. There is a disadvantage that it is difficult to transmit low data.

The apparatus of the present embodiment appropriately takes in the excellent characteristics of these two communication systems to complement each other for the disadvantages of the two communication systems, and has a simple configuration and fail-safe. Is characterized in that it is also considered. Hereinafter, a data processing procedure in the communication node 10 which is a characteristic part of the apparatus of the present embodiment will be described in detail.

FIG. 4 shows the token bus communication circuit 1 described above.
6 shows a flowchart of a data fetching routine executed in the CSMA / CD communication circuit 17.

In the apparatus of this embodiment, whether the data is necessary for its own communication node based on the destination address attached to the data output to the common transmission lines 18 and 19 in any of the above-described systems. No, and the procedure for taking in the data is the same. For this reason, the processing itself is executed separately and independently, but the description thereof will be made with reference to the same flowchart (FIG. 4) for convenience.

As shown in FIG. 4, when the data fetching routine is started, first, data transmitted on the data line, that is, the common transmission line 18 for the token bus or the common transmission line 19 for the CSMA / CD is read (step S1). 100).

When the data reading is completed,
As shown in (1), it is determined whether or not the data is necessary data depending on whether the destination address assigned to the data specifies the communication node 10 (step 102).

If the data is unnecessary, the current processing is terminated. If necessary, the data is stored in a communication buffer connected to the input / output port 15 and the current processing is terminated (step 104). .

As described above, in the multiplex communication apparatus of this embodiment, the token bus system and the CSMA system are always used, regardless of the frequency of data communication performed between the communication nodes.
/ CD communication is performed, and the token bus communication circuit 16 and the CSMA / CD communication circuit 1
The communication buffer 7 is always supplied with data.

For this reason, when compared with a conventional device in which each communication node is connected by a set of common transmission lines and the token bus system and the CSMA / CD system are switched according to the data communication frequency, any one of the common transmission lines is used. Even if the wires 18 and 19 are disconnected, the communication can be continued via the other common transmission path, which is excellent in fail-safe property and simplifies the configuration because a switching mechanism of the communication means is not required. It has the feature that it can achieve.

Incidentally, the data stored in the communication buffers of the token bus communication circuit 16 and the CSMA / CD communication circuit 17 are stored in the RAM 13 via the input / output port 15 in accordance with the later-described processing executed by the CPU 11.

In the RAM 13, as shown in FIG. 5, the RAM 1 area of the internal area serves as a storage area for token bus data, and the RAM 2 area serves as a CSMA /
The storage area for CD data and the RAM 3 area are allocated as areas for storing processing data used as a basis when the communication node 10 executes a predetermined process.
The RAM 3 area stores data appropriately transferred from the RAM 1 and RAM 2 areas.

FIG. 6 shows a flow chart of an example of a data transfer routine executed by the CPU 11 for taking the data stored in each of the communication circuits 16 and 17 into the RAM 13 and storing the data.

FIG. 6A shows a transfer routine from the token bus communication circuit 16 to the RAM 13.
(B) shows the case where the CSMA / CD communication circuit
This is the transfer routine to. These routines also
This is a routine that is started without delay after each of the communication circuits 16 and 17 receives data from the common transmission lines 18 and 19.

That is, when the token bus communication circuit 16 takes in data in accordance with the routine shown in FIG. 4, the routine shown in FIG. 6A is started. Then, in step 200, the data is transferred from the communication buffer of the token bus communication circuit 16 to the RAM1 area.

Next, step 202 is executed, and the RAM 1
Is compared with the data stored during the previous processing to see if the data has been changed. If the data has not been changed, there is no need to update the data, and there is no need to continue the processing.

Then, in step 202, RAM1
If it is determined that there is a change in the data transferred to step (2), the process proceeds to step 204 to update the data, and the data is transferred to the RAM 3, that is, the storage area for processing data.

On the other hand, when the CSMA / CD communication circuit 17 takes in the data, the routine shown in FIG. That is, similarly to the case where the token bus communication circuit fetches data, the case where the data fetched into the RAM 2 from the communication buffer of the CSMA / CD communication circuit 17 has been changed from the data fetched during the previous processing (step 300). (Step 302), the data is transferred from the RAM2 to the RAM3.

That is, when the CPU 11 executes the routine processing shown in FIG. 6, the token bus communication circuit 16 and the CSMA / CD communication circuit 17
Whenever receives data different from the data stored in the RAM1 or RAM2 area, that data is transferred to the RAM3 area.

Therefore, when data is exchanged between the communication nodes by the two communication methods within a small time difference, that is, in a region where data collision by the CSMA / CD method is not a serious problem, The data stored in the RAM 3 area is updated in accordance with the communication method that has detected the change of the data, and it is possible to secure better responsiveness as compared with a device that employs either one of the communication methods alone. Becomes

That is, as shown in the time chart of FIG. 7, the phenomenon that the communication node 10 needs to detect changes from “a” to “b” at time t ₁ ((A) in FIG. 7). Immediately thereafter, the CSMA / CD common transmission path 19
If that condition is transmitted as data via a (FIG. (B)), the RAM2 data is rewritten at time t ₂ (FIG. (C)) simultaneously RAM3 the data is updated.

Therefore, after that, the data "b" is transmitted via the token bus common transmission line 18 (FIG. 2D), and the time t _{3 at which} the data in the RAM 1 is rewritten.
In this case, the data in the RAM 3 area has already been updated, and in this case, the transmission of data by the token bus has substantially no meaning.

On the other hand, when the phenomenon changes from “b” to “c” at time t ₄ , if the transmission by the token bus method is performed faster than the CSMA / CD method due to data collision or the like, , As shown in FIG.
RA at time t ₅ to be rewritten data of AM1 is
The data in the M3 area is also updated at the same time. In this case, when the RAM 2 is rewritten at the time t ₆ , the update of the RAM 3 has already been completed, and the CSMA /
Communication by the CD method has no meaning.

When the state of "c" is maintained thereafter, as shown in FIG.
The data in the AM2 area is not rewritten, and therefore, the data in the RAM3 area is not updated.

As described above, according to the present embodiment,
It is possible to realize duplex communication with a relatively simple structure, to realize a device that is inexpensive and excellent in fail-safeness as compared with a conventional multiplex communication device, and to provide a token bus system. And the advantage of the CSMA / CD system, and high responsiveness can be realized.

The data transfer routine according to the simple update method shown in FIG. 6 is effective when the data communication frequency is relatively low, but the frequency increases.
A problem arises in situations where data transmitted by the SMA / CD scheme has a large delay.

Since the data transmission by the CSMA / CD system may be greatly delayed, the data in the RAM 3 appropriately updated based on the data transmitted by the token bus system may not be transmitted to the CSMA / CD system. This is because data transmitted at a more inappropriate time may cause an improper update.

FIG. 8 is a flowchart showing an example of a data transfer routine executed by the CPU 11 in consideration of preventing such an illegal update of data. This routine is executed by the token bus communication means 16 or the CSMA / C
This is a routine that is started each time one of the D communication units 17 receives data from the common transmission lines 18 and 19.

That is, when the token bus communication circuit 16 or the CSMA / CD communication circuit 17 receives data,
First, the data stored in the communication buffer of the token bus communication circuit 16 is transferred to the RAM 1 (step 40).
0) Then, the data stored in the communication buffer of the CSMA / CD communication circuit 17 is transferred to the RAM 2 (step 402).

In the simple updating method shown in FIG. 6, the reason that the data in the RAM 3 area is updated improperly is that each communication means independently transmits data regardless of data transmission by other communication means. This is because a configuration for updating data is adopted. Further, in such a simple updating method, any one of the communication circuits 1
RAM is also used when the data change is erroneously detected by the
No. 3 data is incorrectly updated.

Therefore, in this routine, after the data has been transferred in steps 400 and 402, it is then determined whether the data transferred to the RAM 1 and the data transferred to the RAM 2 are the same data (step 400). 404), data transfer to the RAM 3 is performed only when the data is the same (step 406).

In this case, the data in the RAM 3 is updated only after it is confirmed that the data transmitted by the token bus method and the data transmitted by the CSMA / CD method are the same. Unauthorized updating of the RAM 3 due to the difference between the data transmission timing and the data transmission timing by the token bus method, or the influence of noise or the like is effectively prevented.

For example, if the transmission of data by the CSMA / CD system is greatly delayed and the contents of the RAM 1 are already rewritten when the data is transmitted, the transmission is delayed by the CSMA / CD system. The contents of the RAM 3 are not updated by the data thus obtained, and malfunction of the communication node 10 is prevented.

In the present embodiment, step 404 shown in FIG. 8 constitutes the same data detecting means.

By the way, when the CPU 11 executes the routine shown in FIG. 8, illegal updating of the data in the RAM 3 can be effectively prevented, but there is a disadvantage that the responsiveness of the data updating is deteriorated.

That is, the data having the higher priority is CSMA /
Even if it is repeatedly transmitted by the CD method,
Unless the data is transmitted by the token bus method, the RAM 3 is not updated. Further, even if data is transmitted at an appropriate time by the token bus method, if the transmission of the data by the CSMA / CD method is delayed, the RAM 3 is updated until the data is transmitted by the CSMA / CD method. There is a situation that it is not performed.

FIG. 9 shows a flowchart of an example of a data transfer routine in consideration of correction of the deterioration of the response. Hereinafter, the operation when the apparatus of the present embodiment executes the processing shown in FIG.

This routine is a routine started after any of the communication circuits 16 and 17 receives data, similarly to the processing shown in FIG.
Step 2 corresponds to steps 400 and 402 in FIG.

That is, when either the token bus communication circuit 16 or the CSMA / CD communication circuit 17 receives data, the data stored in those communication buffers is transferred to the RAM1 and RAM2 (step 50).
0, 502).

Steps 504 to 514 are steps for realizing the above-described event detecting means. After the data in the RAM 3 is updated, the data in the RAM 1 and the data in the RAM 2 become the same or the same data is stored in the RAM 1. Is transferred continuously, or when the same data is continuously transferred to the RAM 2, a process of transferring data constituting the event to the RAM 3 is executed.

That is, in step 504, in steps 500 and 502, RAM1 and RAM2
It is determined whether or not the data transferred to is the same. As described in FIG. 8, when these data are the same, the data can be handled as highly credible data, and the RAM 3 should be immediately updated to this data.

Therefore, in step 504, RAM1
= If it is determined that RAM2 holds, step 5
In step 06, the data that satisfies RAM1 = RAM2 is transferred to RAM3, and the current process ends.

On the other hand, if RAM1 = RAM2 does not hold, the routine proceeds to step 508, where it is determined whether the same data is continuously transferred to RAM1. Where R
The same data is successively transferred to AM1, that is, the reason why the token bus communication circuit 16 continuously receives the same data before RAM1 = RAM2 is satisfied is as follows.
This is a case where data transmission by the CSMA / CD method is significantly delayed.

In this case, it can be estimated that there is no problem regarding the authenticity of the data received by the RAM 1 because the token bus communication circuit 16 receives the same data twice consecutively. That is, in such a case, C
It is ensured that the data in the RAM 1 is correct without waiting for the same data to be transmitted by the SMA / CD method.
M3 should be updated to that data.

For this reason, in this routine, if it is determined in step 508 that the RAM 1 has continuously received the same data, even if the data has not been transmitted yet depending on the CSMA / CD method. Regardless, the process proceeds to step 510 to update the data in the RAM 3 with the data continuously transferred to the RAM 1.

If it is determined in step 508 that the RAM 1 does not continuously receive the same data, the process proceeds to step 512 to determine whether the RAM 2 has continuously received the same data. Ie RAM
1 = CSMA / CD communication circuit 1 before RAM2 is established
7 determines whether the same data has been received continuously.

Such a situation occurs when the same data is successively transmitted by the CSMA / CD system while the data transmission by the token bus system is slightly delayed due to waiting. In this case, the credibility of the data continuously transmitted by the CSMA / CD method can be estimated from the continuity of the same data as having no problem. Further, it is expected that data transmitted continuously by the CSMA / CD method has very high priority.

Therefore, also in this case, the data should be immediately reflected in the control. In this routine, when such a situation is detected in step 512,
Even though the data has not been transmitted yet depending on the token bus system, the process proceeds to step 514 to transfer the data continuously received by the RAM 2 to the RAM 3.

When it is determined in step 512 that the RAM 2 has not received the same data continuously,
Since there is no basis for updating the data in the RAM 3, the current process ends.

The operation and effect when the CPU 11 executes this routine will be described below with reference to a time chart shown in FIG.

That is, as shown in FIG. 10A, when the phenomenon changes from “a” to “b” at time t ₁ , as shown in FIG.
When the data representing the phenomenon is transmitted to the common transmission line 19 for MA / CD, at time t ₂ is rewritten to "b" from RAM2 is "a" (FIG. (C)).

In this case, according to the simple updating method described above, the RAM 3 is updated to "b" as shown in FIG. 9G, but when this routine is executed,
Since none of the conditions in steps 504, 508, and 512 are satisfied, the RAM 3 is not updated yet (FIG. 9F).

Then, the common transmission path for the token bus
Is transmitted at time t _ThreeRAM1 at
Is rewritten to "b", RAM1 = RAM
2 holds, the RAM 3 is updated to "b".
You.

Subsequently, when the phenomenon changes from “b” to “c” as shown in FIG.
Both the / CD common transmission path 19 and the token bus common transmission path 18 generate a data transmission request reflecting the change in the situation. Here, the case of a token bus method, it is not possible to send the request is blocked, the time t ₅ to slightly delayed from happening time t ₄ phenomena change, R
AM1 is surely rewritten to "c".

On the other hand, in the CSMA / CD system, when the common transmission line 19 is occupied by other data having a high priority, the transmission is stopped as described above, and the common transmission line becomes available again. This is the method in which the retransmission is performed after waiting for. Therefore, depending on the timing at which the transmission request occurs, a large waiting time may occur before the data is actually transmitted.

For example, FIG. 10 shows a case where data indicating that the data has changed to “c” at time t ₄ is retransmitted with a considerable delay. In this case, to change the RAM2 is "c" to be rewritten on the basis of the received data CSMA / CD communication circuit 17 as shown in FIG. (C), the timing greatly delayed from the time t _4.

Therefore, if a configuration is employed in which the RAM 3 is rewritten only when the condition of RAM 1 = RAM 2 is satisfied, the update time of the RAM 3 is greatly delayed, and during that time,
In view of the possibility that AM2 has changed, a situation may occur in which the update time of RAM3 is significantly delayed.

On the other hand, in this routine, R
When the AM1 or the RAM2 continuously receives the same data, the content of the RAM3 is updated by trusting the data.

Therefore, as shown in FIG.
/ Even "c" data in the common transmission path for CD is a case where the delay increases by collisions, then continued phenomenon "c" until the time t _7, 2 time the token bus for common transmission line 18 at time t ₆ If the "c" signal is issued, the signal the occurrence of the (time t ₆₎ RAM 3 is "c" data is transferred, so that the proper update of the data is performed.

[0106] Hereinafter, the phenomenon is changed to "b" at time t _7, when the "b" data to the common transmission line 18 for the token bus is transmitted, RAM 1 at time t ₈ is changed to "b" As a result, RAM1 = RAM2 is established, and RAM3 is immediately updated to "b".

Then, after a long delay, CSMA / C
Even if the RAM 2 is rewritten to “c” due to the “c” data transmitted to the D common transmission line 19,
Since 1 has changed to "b", unlike the case of the simple update method, the RAM 3 is not rewritten to "c".

As described above, when the CPU 11 executes this routine, even if the transmission time of the data by the CSMA / CD system and the transmission time of the data by the token bus system are greatly shifted, the difference is not changed. Due to RAM
No. 3 data is not updated to incorrect data. In addition, although a slight time delay occurs, it is possible to appropriately update data following the change in the phenomenon.

Therefore, when the communication node 10 executes the present routine processing, it is possible to execute control based on appropriate accuracy and responsiveness without malfunction in the communication node 10.

[0110]

As described above, according to the first aspect of the present invention, the data processing means transmits data based on the processing.
In addition to being able to increase possession, CSMA / C
Highly important data is repeatedly transmitted by D method
In that case, the data is immediately reflected in the processing, and C
For data whose transmission is greatly delayed in SMA / CD system
About the data transmitted by the token bus method.
The control can be reflected at a more appropriate time.

[0111]

[0112]

[0113] Therefore, according to the multiplex communication system according to the present invention has the advantage that it is possible to improve the processing of the response and accuracy.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a multiplex communication system according to the present invention.

FIG. 2 is a block diagram of a communication node which is a main part of the multiplex communication system according to one embodiment of the present invention.

FIG. 3 is an example of a data frame in a communication system used in the apparatus of the embodiment.

FIG. 4 is a flowchart illustrating an example of a data fetching routine executed by a communication circuit of the apparatus according to the embodiment.

FIG. 5 is a diagram showing allocation of a data storage area in a RAM of the device of the embodiment.

FIG. 6 is a flowchart illustrating an example of a data transfer routine executed by a CPU of the apparatus according to the embodiment.

FIG. 7 is a time chart (No. 1) illustrating a data transfer operation of the device of the present embodiment.

FIG. 8 is a flowchart of another example of the data transfer routine executed by the CPU of the apparatus of the embodiment.

FIG. 9 is a flowchart of another example of the data transfer routine executed by the CPU of the apparatus of the embodiment.

FIG. 10 is a time chart (No. 2) illustrating a data transfer operation of the device of the present embodiment.

[Explanation of symbols]

N ₁ ~N _n, 10 communication node T ₁ through T _n token bus communication means C ₁ ~C _n CSMA / CD communication unit D ₁ to D _n data processing means L _T, 18 token bus common transmission path L _C, 19 Common transmission line for CSMA / CD 11 Central processing unit (CPU) 12 Common bus 13 Random access memory (RAM) 14 Read only memory (ROM) 15 I / O port

Claims (1)

(57) [Claims] 1. Token bus communication means for transmitting data according to a preset order by the token bus system while receiving necessary data and transmitting / receiving data .
According to the C SMA / CD method, priority is given to data to be transmitted, and when collision occurs with higher priority data, transmission of the data is stopped to avoid data collision, while necessary data is received. CSMA / C to send and receive data
And D communication means, before Symbol token bus communication means and the CS
With MA / CD communication means to execute a predetermined process based on the received data, each having a data processing means for supplying the same data, the to the token bus communication unit and the CSMA / CD communication means CSMA connecting a plurality of communication nodes, and a common transmission path for the token bus connecting between the token bus communication unit of the plurality of communication nodes, between the CSMA / CD communication means of the plurality of communication nodes
Contact / common transmission path for CD, the multiplex communication system comprising a
And the data processing means executes the predetermined processing.
After the token bus communication means and the C
The data received by the SMA / CD communication means is the same
That the token bus communication means continuously has the same data.
Data, and said CSMA / CD communication means
Are the first to receive the same data consecutively.
Event detecting means for detecting a generated event, wherein the data processing means detects the event by the event detecting means.
The predetermined processing based on the data constituting the event
A multiplex communication system characterized by performing: