JPH09181754A - Communication control system and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the real time nature of data by placing a higher transmission priority onto a frame as required in the case of sending a frame with a lower priority to avoid interruption of frame transfer. SOLUTION: In the case that a transmission station 10 sends a frame to a reception station 20, the transmission station 20 tries 2nd frame transmission because no reply comes from the reception station 20 and further no reply is received from the reception station 20, a CPU of the transmission station 10 sets a higher priority than the priority for the preceding transmission to a priority revision area in an arbitration field in the transfer frame as a frame with higher transmission priority and sends the frame to the reception station 20. When the transfer of this frame is finished, the transmission station 10 restores the bit information stored in the priority revision area to the original priority and continues the transmission of the frame in this state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CSMA / NBA (Carrier Sense Mult) which transfers a transfer frame having the highest priority when a plurality of frames collide.
iple Access with Non-destructive Bitwise Arbitratio
n) A communication control system and a communication control method using a communication method.

[0002]

2. Description of the Related Art In recent years, C has been added to in-vehicle multiplex communication networks.
AN (Controll Area Network) is beginning to be used,
A CSMA / NBA communication system is adopted for this CAN.

In this CSMA / NBA communication system, the transmitting station itself constantly monitors the frames of its own station and the frames of other stations, and when a plurality of frames collide with each other on the bus, the frame of its own station is detected. And the transmission priority of the frames of other stations is compared, and as a result, the transmission station that has transferred the frame with the highest transmission priority is allowed to continue to transfer frames, and the transmission that transfers other frames is sent. This is a method in which the station suspends frame transfer.

The CSMA / NBA communication system will be described in more detail.

First, a frame used in this communication system will be described. For example, as shown in FIG.
The frame 60 is composed of a header field 61, a data field 62 in which data is stored, and a tail field 63 in which a CRC code for error check and the like are stored. The header field has a unique transmission priority. It has an arbitration field 611 for storing the transmission priority information shown, and the bits constituting this arbitration field 611 are assigned the properties as a dominant bit (for example, “0”) and a recessive bit (for example, “1”). Has been.

When a plurality of such frames collide, each transmitting station that has transferred the frame compares the transmission priorities of its own frame and the frames of other stations as follows. That is, each transmitting station sets the arbitration field 611 in the frame for the frame of its own station and the frame of the other station to the first bit (most significant bit).
The bit superiority is determined in the order from the lower bit to the highest priority frame, that is, the frame having the highest transmission priority is specified.

As a result, when each transmitting station determines that the frame transferred by itself is not the frame with the highest transmission priority, it suspends the transfer of that frame, while having the highest transmission priority. If it is determined that it is the one, the frame transfer is continued as it is, and the bus right is monopolized.

The above description will be described in detail with reference to FIG. 11. When the frames output from the transmitting station 1, the transmitting station 2 and the transmitting station 3 collide with each other, as shown in FIG. The first bit of the station 1 and the transmitting station 3 is “0” indicating the dominant bit, whereas that of the transmitting station 2 is “1” indicating the recessive bit, so the transmitting station 2 outputs itself. It recognizes that the frame has a lower transmission priority than the frames from the transmitting station 1 and the transmitting station 3, interrupts the transmission, and changes from the transmitting station to the receiving station.

Next, regarding the frames from the remaining transmitting stations 1 and 3, the second bit to the lower bit are sequentially
When the superiority is checked, the fourth bit of the transmitting station 1 is “0” indicating the dominant bit, while that of the transmitting station 3 is “1” indicating the inferior bit. Is
The frame output by itself is recognized as a frame having a lower transmission priority than the frame output by the transmitting station 1, the transmission is interrupted, and the transmitting station changes to the receiving station.

Therefore, the last remaining transmitting station 1 monopolizes the bus right and continues to transfer its own frame as it is.

As described above, the communication control system using the CSMA / NBA communication method, when transferring a frame having a high transmission priority, is, for example, a conventional CSMA / NBA communication system.
CD (Carrier Sense Multiple Access with Collision
Detection) When a frame collides like a communication control system using a communication method, there is no need to perform frame retransmission processing, and there is an advantage that the real-time property of data is good.

[0012]

However, in the communication control system using the conventional CSMA / NBA communication system as described above, the transmission priority is fixed.
When a frame with a low transmission priority is transmitted, when the frame transmission from another station occurs frequently, the transmitted frame collides with a frame with a high priority from another station on the bus. , A transmitting station that has transferred a frame with a lower transmission priority always determines that its own frame has a lower transmission priority than frames from other stations, even if the same frame is repeatedly transmitted, and Since there is no choice but to interrupt the transfer, there is a problem that it is difficult to transfer the data in real time.

Further, even if the transmission is finally made several times, since the receiving station (management station) is performing the error processing due to the time-out, the receiving station cannot receive this frame and must continue transmitting again. Therefore, there is a problem that it is difficult to transmit data in real time.

In view of the above-mentioned problems, the present invention makes the transmission priority variable so that the transmission priority of the frame can be increased as necessary even when transmitting a frame having a low transmission priority. CSMA that improves the real-time property of data by avoiding interruption of transfer
An object of the present invention is to provide a communication control system and a communication control method using the / NBA communication method.

[0015]

In order to achieve the above-mentioned object, the invention according to claim 1 has transmission priority information in a frame transferred between a transmitting station and a receiving station, When the above frames collide, the CSMA / NBA that transfers the transfer frame with the highest transmission priority
In the communication control system based on the communication method, the transmitting station has a transmission priority changing means for changing the transmission priority information.

According to a second aspect of the present invention, in the first aspect of the invention, when the transmitting station cannot transmit to another station for a certain period of time, or cannot transmit to another station continuously for a certain number of times. In either of the cases,
It is characterized by further comprising transmission priority changing means for changing the transmission priority information.

According to a third aspect of the present invention, in the case of the first aspect of the present invention, the transmission station has a management station that monitors a frame transfer status, and the transmission station cannot transmit to another station for a certain period of time. , And in the case where it is not possible to transmit to another station for a certain number of times continuously, send a transmission stop request to all other stations to the control station to the effect that frame transmission should be stopped. When the management station receives a transmission stop request from the transmitting station, the control station has a transmission stop request transfer means, and transmits a transmission stop command for stopping the frame transmission to all other stations. It is characterized by having an instruction transmitting means.

According to a fourth aspect of the present invention, in the case of the first aspect of the present invention, the transmission station has a management station for monitoring the frame transfer status, and the transmission station cannot transmit to another station for a certain period of time. , And in the case where it is not possible to transmit to another station continuously for a certain number of times, it has a priority change request transmitting means for transmitting a priority change request of the transfer frame to the management station. The management station has a priority setting notifying means for transmitting the priority setting notification to the transmitting station upon receiving a priority change request from the transmitting station.

According to a fifth aspect of the present invention, in the case of the first aspect of the present invention, the transmission station has a management station for monitoring the frame transfer status, and the transmission station cannot transmit to another station for a certain period of time. , And in the case where it is not possible to transmit to another station continuously for a certain number of times, it has a priority change request transmitting means for transmitting a priority change request of the transfer frame to the management station. When the management station receives a priority change request from the transmission station, the management station determines whether or not there is a transmission priority assigned to the transmission station, and the priority presence / absence determination means transmits the transmission. If it is determined that there is a transmission priority to be assigned to a station, this assignable transmission priority is transferred to the transmitting station, while if it is determined that there is no transmission priority to be assigned to the transmitting station, another station is assigned. Transfer of And a sending priority notifying means for transferring to said transmission station transmission priority of frames as a transmission priority can be allocated.

According to a sixth aspect of the invention, in the first aspect of the invention, the stations have a parent-child relationship, and the parent station transmits a response confirmation request to the receiving station as a child station. When there is no response from the response confirmation request transmitting means and the slave station even after a fixed time has passed, and when there is no response even after a constant number of times of continuous transmission, the priority change notification is transmitted to the non-responsive child. And a priority change notification transmitting means for transmitting to the station.

According to a seventh aspect of the invention, in the invention according to any one of the first to sixth aspects, the transfer frame has a transmission priority information storage field for storing the transmission priority information. The transmission priority changing means changes the transmission priority of the transfer frame by changing the transmission priority information stored in the transmission priority information storage field.

The invention according to claim 8 has the transmission priority information in the frame transferred between the transmitting station and the receiving station,
When a plurality of the above-mentioned frames collide, the transfer frame with the highest transmission priority is transferred to CSMA /
In the communication control method based on the NBA communication method, the transmitting station changes the transmission priority information.

According to the present invention, since the transmitting station changes the transmission priority information of the transfer frame as necessary, when the frame transmission from another station occurs frequently,
Frames can be transferred without interruption.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a communication control system and a communication control method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a communication control system according to the present invention.

The communication control system of this embodiment is a communication control system using the CSMA / NBA communication system, which transfers the transfer frame having the highest transmission priority when a plurality of frames collide. , Stations # 1 to #n are provided on the communication line 1, and a communication device 22 is provided in the node 21 of each station.

The communication device 22 is, as shown in FIG.
It is composed of a transceiver 221 that transmits and receives frames to and from the communication line 1, a communication control unit 222 that performs error check control and the like in frame units, a CPU 223, a memory 224 that stores a communication control program, and an external interface 225 that interfaces with external equipment. There is.

Here, the CPU 33 is configured to control data transmission / reception to / from the communication control unit, control an external interface, monitor transmission timing, confirm delivery of data, and change transmission priority.

FIG. 3 is a block diagram of a frame used in the communication control system of this embodiment.

As shown in the figure, the frame 4 includes a header field 41 and a data field (D).
ata Field 42 and tail field
) 43.

Here, the header field 41 has an arbitration field 411 consisting of 11 bits, and this arbitration field 411 is
A 5-bit transmission priority storage area 41a for storing information indicating the transmission priority of the own station, and a node ID area 41b storing a node ID of the own station and a node ID indicating the frame transfer destination. It is configured.

Further, the transmission priority storage area 41a is
A priority change area 4aa for storing information for changing the transmission priority of its own station, which is composed of the first bit and the second bit of the arbitration field 411, and each application processed by the CPU 33, which is composed of the third bit to the fifth bit It is configured with a unique priority area 4ab that stores information indicating a unique transmission priority.

The bits constituting the arbitration field 611 are assigned the property as a dominant bit or a recessive bit depending on the information value to be stored.

For example, a bit storing "0" is a dominant bit, and a bit storing "1" is a recessive bit.

Therefore, the arbitration field 6
If the information stored in No. 11 is the following frame, "00011000101" frame A "01001100010" frame B frame A has the second bit "0" and frame B has "1". Since it is ", the frame A is the frame B
The transmission priority is higher than that of

The data field 42 is a field in which data to be transferred is stored for each character.

The tail field 43 indicates the type of the transmitted frame (for example, a data frame for transferring data, a frame such as an error frame transmitted when the frame transmitted / received by the communication control unit 32 has an error). This is a field in which information and a CRC code, which is a cyclic code for checking an error of a transmitted frame, are stored.

Next, the operation of the communication control system of this embodiment will be described with reference to FIGS.

FIG. 4 is an explanatory view for explaining the communication procedure of the communication control system of the first embodiment.

The communication procedure of the communication control system shown in FIG. 4 is such that when the transmitting station cannot transmit for a certain time or a certain number of times, the transmitting station itself changes the transmission priority,
It shows a procedure for transmitting data.

When the transmitting station 10 transmits a frame to the receiving station 20, there is no response from the receiving station 20, so that the frame is continuously transmitted. Nevertheless, when there is no response from the receiving station 20 (see the figure and reference), the CPU 33 of the transmitting station 10 sets the priority change area 4aa in the arbitration field 411 in the transfer frame to a bit more dominant than the previous time. Is set and this frame is transmitted to the receiving station (see).

For example, if the last time is "01", this time is set to "00" and transmitted to the receiving station.

When this frame has been transferred, the CPU 33 of the transmitting station 10 causes the priority changing area 4
Change the bit information stored in aa to the original state,
Continue transmitting frames in this state (see).

In this embodiment, when the frame cannot be transmitted three times in succession, the transmission priority of the frame is set high.
The frame transmission priority may be increased when the response time to the frame transmission becomes a certain time or more.

FIG. 5 is an explanatory view for explaining the communication procedure of the communication control system of the second embodiment.

In the communication procedure of the communication control system shown in FIG. 5, the transmitting station issues a transmission stop request to the management station, the management station stops transmission to all stations, and then the transmitting station It shows a procedure for performing data transfer.

The transmitting station 10 is transmitting a frame to the receiving station 20 (see also), and when a certain frame is being transmitted to a predetermined receiving station 20 and this frame becomes untransmittable due to timeout (see), By similar means,
A transmission stop request having a high transmission priority is transmitted to the management station 30 (see).

Upon receiving the transmission stop request from the transmitting station, the management station 30 broadcasts a transmission stop command having a high transmission priority to all other stations (reception stations) 20 (see).

Then, the receiving station 20 receiving this command
It returns a response to the management station 30 (and reference).

When there is a receiving station 20 that does not respond, the management station 30 retransmits the transmission stop command to the receiving station 20 that does not respond a predetermined number of times until a response is received. However, the management station 30 determines that the receiving station 20 does not exist when there is no response even if the transmission stop command is retransmitted a predetermined number of times.

In this way, the management station 30 sends a data transfer permission to the transmitting station when there is a response from all the receiving stations 20 (see).

Upon receiving the data transfer permission from the management station 30, the transmitting station 10 transmits data (see a).

When the transmitting station 10 finishes transmitting the data, the management station 30 broadcasts permission to restart the transmission of the frame to all other stations 20 (see b).

It should be noted that the transmitting station 10 can receive the permission for the management station 30 to restart the transmission of the above-mentioned frame while broadcasting the permission.
Sending data (see c).

In this embodiment, when the frame cannot be transmitted three times in a row, the frame transmission priority is set to be high, but in other cases, the response time to the frame transmission is set. However, the transmission priority of the frame may be increased when a certain time or more has elapsed.

FIG. 6 is an explanatory view for explaining the communication procedure of the communication control system of the third embodiment.

In the communication procedure of the communication control system shown in FIG. 6, the transmitting station issues a transmission priority change request to the management station, the management station gives a new transmission priority to the transmitting station, and then, It shows a procedure in which the transmitting station transfers data with the transmission priority.

The transmitting station 10 is transmitting a frame to the receiving station 20, and while the data (frame) is being transmitted to the predetermined receiving station 20, if this data becomes time-out disabled for transmission (and reference), the high transmission A transmission priority change request is transmitted to the management station to request the priority (see).

The management station 30 sends the priority change request to the transmitting station 1
When it is received from 0, a priority notification indicating a transmission priority higher than the previous transmission priority is transmitted to the transmitting station 10 (see).

Upon receiving the priority notification from the management station 30, the transmission station 10 transmits the frame (data) having the transmission priority notified by the management station 30 to the reception station 20 (see). That is, the transmitting station 10 changes the value of the transmission priority storage area 41a in the arbitration field 411 to transmit the data having the high transmission priority to the receiving station 20.

When the transmitting station 10 finishes transmitting the data with the transmission frequency notified from the management station 30 for the expected number of times or time (see), it transmits the data with the original priority (see).

FIG. 7 is an explanatory view for explaining the communication procedure of the communication control system of the fourth embodiment.

The communication procedure of the communication control system shown in FIG. 7 is similar to that of FIG. 6, in which the transmitting station issues a transmission priority change request to the management station, and the management station sends a new transmission priority to the transmitting station. This is a procedure for giving a priority and then the transmitting station transfers data at the transmission priority. However, there are differences as described below as a method of giving a new transmission priority to the transmitting station.

The transmitting station 10 is transmitting a frame to the receiving station 20, and while the data (frame) is being transmitted to a predetermined receiving station 20, if the data becomes untransmittable due to a timeout (see, and), the high transmission A transmission priority change request is transmitted to the management station to request the priority (see).

The management station 30 sends the priority change request to the transmitting station 1
When receiving from 0, it is determined whether or not there is a transmission priority assigned to the transmitting station 10, and when it is determined that there is a transmission priority assigned to the transmitting station 10, the assignable transmission priority is determined. On the other hand, when it is determined that there is no transmission priority to be assigned, the transmission priority given to the station 40 having the highest priority and the smallest amount of transmission / reception at that time can be lowered and assigned. It is transferred to the transmitting station 10 as the transmission priority.

That is, the management station 20 constantly monitors the station with the highest priority and the least amount of transmission / reception, and the transmission station 10
When a priority change request is received from the specified station 40, the corresponding station 40 is specified at that time, a priority change notification is transmitted to the specified station 40 (see), and a response thereto is received (see). , And sends a notification indicating the new transmission priority to the transmitting station 10 (see).

Upon receiving the notification of the new transmission priority notification from the management station 30, the transmission station 10 transmits the frame (data) having the new transmission priority to the reception station 20 (see).

FIG. 8 is an explanatory view for explaining the communication procedure of the communication control system of the fifth embodiment.

The communication procedure of the communication control system shown in FIG. 8 is such that when there is a parent-child relationship between the stations, when there is no response from the child station for a certain period of time or a certain number of times expected by the parent station, the parent station responds It shows a procedure for assigning a new transmission priority to a slave station that does not have a.

The master station 50 is connected to the slave station (reception station) 55 at any time.
Sending a confirmation request (and see),
If there is no response from the slave station 55 after a certain period of time, or if there is no response from the slave station 55 even after continuously transmitting a certain number of times, the slave station 55 has a low transmission priority. The station 55 determines that it cannot respond, and sends a priority change notification to the slave station 55 (see).

Upon receiving the priority change notification from the master station 50, the slave station 55 responds to the master station 50 with a transmission priority higher than the original transmission priority (see).

The master station 50 sends a priority change notification to the slave station 5.
Even if 5 is notified, if there is no response for a certain period of time, this notification is issued again and the response is awaited, and if there is still no response, abnormal processing may be performed. For example, assuming that the slave station 55 itself does not exist, the response confirmation request is not transmitted thereafter.

FIG. 9 is a block diagram showing the configuration of another communication device used in the present invention.

The communication device 32 has a configuration similar to that of the communication device 22 in the above-described embodiment, except that the state monitoring unit 327, the CPU I / F unit 328 and the memory 3 are used.
29 is newly added and configured.

Here, the state monitoring unit 327 monitors the transmission state of the transmitting / receiving station which was handled by the CPU 223 of FIG. 2 described above, and the memory 328 is the memory CPU 22 described above.
4 stores the communication control program for monitoring the transmission state of the transmission / reception station among the communication control programs stored in No. 4, and the CPU I / F unit 328 interfaces with the CPU 323.

[0076]

According to the present invention, since the transmitting station can change the transmission priority information of the transfer frame as necessary, the transmitting station can increase the transmission priority of the frame and transmit the frame. Especially when the frame transmission from other stations occurs frequently, by increasing the transmission priority of the frame,
Transmission interruption can be avoided, and as a result, real-time performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a communication control system according to the present invention.

FIG. 2 is a block diagram showing the configuration of the communication device in FIG.

FIG. 3 is a block diagram of a frame used in the communication control system of the present embodiment.

FIG. 4 is an explanatory diagram illustrating a communication procedure of the communication control system of the present embodiment.

FIG. 5 is an explanatory diagram illustrating a communication procedure of the communication control system of the present embodiment.

FIG. 6 is an explanatory diagram illustrating a communication procedure of the communication control system of the present embodiment.

FIG. 7 is an explanatory diagram illustrating a communication procedure of the communication control system of the present embodiment.

FIG. 8 is an explanatory diagram illustrating a communication procedure of the communication control system of the present embodiment.

FIG. 9 is a block diagram showing the configuration of another communication device.

FIG. 10 is a block diagram showing a frame used in a conventional communication control system.

FIG. 11 is an explanatory diagram illustrating a method of determining a frame to acquire a bus right when a frame collides in a conventional communication control system.

[Explanation of symbols]

1 Communication Line 2 40 Station 10 Transmitting Station 20 Receiving Station 30 Management Station 50 Master Station 55 Slave Station 21 Node 22, 32 Communication Equipment 221, 321 Transceiver 222, 325 Communication Control Unit 223, 323 CPU 224, 324, 329 Memory 225 , 325 External interface 328 CPU I / F section 4 frame 41 Header field 42 Data field 43 Tail field 411 Arbitration field 41a Transmission priority storage area 41b Node ID area 4aa Priority change area 4ab Unique priority area

Claims (8)

[Claims] 1. The transmission priority information is included in the frame transferred between the transmitting station and the receiving station, and when a plurality of the frames collide with each other, the transfer frame having the highest transmission priority is transferred. In the communication control system according to the CSMA / NBA communication method described above, the transmission station includes a transmission priority changing unit that changes the transmission priority information. 2. The transmission priority is given when the transmitting station cannot transmit to another station for a certain period of time or when it cannot transmit to another station continuously for a certain number of times. The communication control system according to claim 1, further comprising transmission priority changing means for changing the degree information. 3. A management station for monitoring the frame transfer status is provided, and the transmission station can transmit to another station when it cannot transmit to another station for a certain period of time or when it continuously transmits to another station for a certain number of times. In any one of the cases where it is not possible, it has a transmission stop request transfer means for transmitting to all the other stations a transmission stop request to the management station to the effect that frame transmission should be stopped. 2. The apparatus according to claim 1, further comprising a transmission stop command transmitting means for transmitting a transmission stop command for stopping frame transmission to all other stations when receiving a transmission stop request from the transmitting station. Communication control system. 4. A management station for monitoring the frame transfer status is provided, and the transmission station can transmit to another station when it cannot transmit to another station for a certain period of time or when it continuously transmits to another station for a certain number of times. In any of the cases where it is not possible, it has a priority change request transmitting means for transmitting a priority change request of the transfer frame to the management station, while the management station sends a priority change request from the transmission station. 2. The communication control system according to claim 1, further comprising a priority setting notifying means for transmitting the priority setting notification to the transmitting station upon receiving the priority setting notification. 5. A management station for monitoring a frame transfer status is provided, and the transmission station can transmit to another station when it cannot transmit to another station for a certain period of time or when it continuously transmits to another station for a certain number of times. In any of the cases where it is not possible, it has a priority change request transmitting means for transmitting a priority change request of the transfer frame to the management station, while the management station sends a priority change request from the transmission station. When receiving the priority, the priority presence / absence determining means for determining whether or not there is a transmission priority assigned to the transmitting station, and the priority presence / absence determining means determining that there is a transmission priority assigned to the transmitting station, , While assigning the assignable transmission priority to the transmitting station, if it is determined that there is no assigning transmission priority to the transmitting station, the assigning transmission priority of the transfer frame of another station can be assigned. The communication control system according to claim 1, characterized in that it has a transmission priority notifying means for transferring to said transmission station by. 6. The station has a parent-child relationship, and the transmitting station includes a response confirmation request transmitting unit for transmitting a response confirmation request to a receiving station as a slave station, and the child station. If there is no response from the station even after a certain period of time has passed, or if there is no response after a certain number of consecutive transmissions,
The communication control system according to claim 1, further comprising: a priority change notification transmitting unit that transmits a priority change notification to the slave station that does not respond. 7. The transfer frame has a transmission priority information storage field for storing the transmission priority information, and the transmission priority changing unit is stored in the transmission priority information storage field. 7. The communication control system according to claim 1, wherein the transmission priority of the transfer frame is changed by changing the existing transmission priority information. A communication control system comprising: 8. The transmission priority information is included in a frame transferred between the transmitting station and the receiving station, and when a plurality of the frames collide with each other, the transfer frame having the highest transmission priority is transferred. In the communication control method according to the CSMA / NBA communication method described above, the transmission station changes the transmission priority information.