JP3628042B2 - Multiple communication method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a multiplex communication method in which, when multiplex communication is applied to vehicle electrical equipment, the influence is suppressed even when a communication abnormality occurs, and good responsiveness can be secured.
[0002]
[Prior art]
In the conventional vehicle electrical equipment, each electronic device is connected by wiring of the number of signals necessary for each of switch inputs, sensor outputs, actuator drive signals, and the like. However, as the electrical system becomes more complex as the vehicle becomes more sophisticated, problems such as deterioration in layout due to an increase in the number of wires, increase in weight, and deterioration in workability during assembly have occurred. Has come to be done.
FIG. 7 shows an example of vehicle electrical equipment using a multiple communication system. One communication master station 101 having the microcomputer 110 is mounted under the driver seat instrument, and the slave station has two slave stations 102 to 105 in the driver seat door 143 and the passenger seat door 144, respectively, The left and right doors 145 and 146 are each equipped with one slave station 106 and 107, and the driver and passenger seats 147 and 148 are respectively installed with one slave station 108 and 109. A communication line 142 connects between the communication IC 111 in the master station 101 and the communication IC 112 built in each slave station, and the input / output ports of each slave station communication IC 112 are connected via the input / output circuits 113 to 120. The motors 131 to 141 and the switches 121 to 139 are connected. Each of the slave stations 102 to 109 has a function of receiving transmission of the output command from the master station 101, driving the motor in accordance with this, and transmitting the status of the switch input signal of the slave station itself as a reply to the master station. ing. Control of each electrical function and communication function is performed by the master station 101 controlling input / output of the slave stations 102 to 109 via the communication line 142.
[0003]
An example of the communication waveform and its format is shown in FIG. The communication signal includes a communication start code 201 indicating the start of the communication signal, a command frame 202 for identifying whether transmission is performed by the master station or the slave station, a slave station address frame 203 indicating a transmission destination or a transmission source, and a data frame 204 indicating input / output data. 205, a communication end code 206 indicating the end of the communication signal, and parity bits 207 to 209 for detecting an abnormality of the communication signal are also provided. Each slave station 102 to 109 has a unique address that is not duplicated, and the input / output port of the communication IC 112 of the slave station and each bit of the data frame are assigned in a one-to-one correspondence.
FIG. 9 shows an example of a communication procedure. The master station 101 transmits the address and output data of the access slave station under the control of the microcomputer 110 (301 to 304). Of each slave station, only the slave station that has recognized its own address performs load drive output according to the received output data, and simultaneously returns its own address and its input data to the master station 101 (305-308). . On the other hand, the communication IC 111 of the master station that has received a reply from the slave station transmits the input data of the slave station to the microcomputer. The master station 101 accesses each slave station in a predetermined order and repeats this operation.
Actually, the process from the operation of the driver seat power seat switch 121 to the operation of the driver seat power seat motor 140 in FIG. 7 will be described. While performing the communication procedure described above, the master station microcomputer 110 captures data indicating that the switch has been operated from the power seat switch slave station 102 via the communication IC 111. The microcomputer calculates in accordance with the control logic, determines to output the power seat motor 140, and accesses the next slave station. When access to each slave station is repeated and eventually the power sheet slave station 108 is accessed, the master station 101 transmits a power seat motor output command. Receiving this, the power seat slave station 108 drives the power seat motor 140.
[0004]
[Problems to be solved by the invention]
When introducing the multiplex communication system as described above into a vehicle, it is necessary to consider the possibility of destruction of communication signals due to noise mixing. For example, a high-frequency surge that occurs when a relay that exists in various places in a vehicle is turned on / off may reach several hundred volts, and when this enters the communication line due to capacitive coupling between the wirings, the waveform of the communication signal is distorted, There are cases where normal I / O data transfer is hindered. Normally, in each communication unit, data check by parity, pulse width, format check, address check, no response detection, etc. are performed by the communication IC or microcomputer, and when such communication abnormality occurs, normal reception is performed. Conventionally, the process of prohibiting the update of input / output data until it has been performed is normal. When such a method is used, once an abnormality occurs when accessing a certain slave station, the communication sequence is completed, until the next access order with that slave station and normal communication is performed, etc. The load drive output of is maintained. Therefore, the time until the change of the switch input is reflected in the operation of the load becomes long, and the response is deteriorated. In particular, when communication abnormality occurs during communication with a slave station having a switch input that changes relatively frequently, the deterioration of responsiveness may cause malfunction.
As a countermeasure against such a situation, it is common to retransmit from the master station. That is, when the master station detects an abnormality in the reply from the slave station, data is transmitted again to the same slave station without moving to the next slave station. Of course, a permanent unit failure, a disconnection of a communication line, a short circuit, and the like are also conceivable. Therefore, it is necessary to limit the number of retransmissions to each slave station.
In the conventional multiplex communication method as described above, the larger the retransmission limit, the more effective the retransmission. However, there are many communication anomalies during the entire communication sequence (hereinafter referred to as a communication cycle). When it occurs, the communication cycle becomes longer than the state transition cycle of the input signal, it becomes impossible to capture the change of the accurate input signal, or it takes time to retransmit to the slave station having the input signal with a long state transition cycle, There may be a problem that an access interval with a slave station having an input signal with a short state transition cycle, that is, an update period of input data becomes long and an accurate change of the input signal cannot be captured.
It is an object of the present invention to provide a multiplex communication method that prevents the above-described conventional problems from occurring.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, one master station and a plurality of slave stations are connected by multiple communication lines, and the master station first transmits to one slave station, and then receives this transmission. In the multiplex communication method in which an access operation of receiving a reply from a slave station is sequentially performed on each slave station according to a predetermined access order, and a fixed pattern of the access order is repeated as one communication cycle, the master station When the reply from the slave station is received normally, the access operation with the next slave station is performed according to the above access sequence, and when an abnormality is detected in the reply from the slave station, a predetermined retransmission condition is satisfied. In this case, retransmission is performed to the same slave station, and if the retransmission condition is not satisfied, the access operation with the next slave station is performed in accordance with the above access order. Retransmission counter that counts the number of retransmissions for each slave station, and retransmission total counter that counts the number of retransmissions to all the slave stations during one communication cycle, or accesses each slave station by retransmission A retransmission time counter for counting the total time required for the transmission, the count value of the retransmission counter being equal to or less than a specific value predetermined for each slave station, and the retransmission total counter or the retransmission time When the count value of the counter is equal to or less than a predetermined value, it is assumed that the retransmission condition is satisfied.
[0006]
[Action]
In the present invention, for the retransmission operation performed from the master station toward the slave station when an abnormality occurs in the multiplex communication system, not only provides a limit on the number of retransmissions for each slave station as in the past, According to the retransmission condition according to the present invention, the total number of retransmission operations per communication cycle or the upper limit of the total time spent for the retransmission operation is set. Therefore, when an abnormality occurs, it is unavoidable for the retransmission operation. It does not take a long time, and the time of one communication cycle can be moderately suppressed. The communication cycle is longer than the state transition cycle of the input signal, so that the change of the input signal cannot be captured accurately. Time is spent retransmitting to a slave station with a long input signal, and the access interval with the slave station having an input signal with a short state transition cycle, that is, the update cycle of input data becomes longer. It is possible to solve problems such as not captured accurate input signals. According to the present invention, as the communication (access) order from the master station to the slave station is later in the communication cycle, the retransmission total counter and the retransmission time counter may have already made retransmission impossible when an abnormality is detected. Is expensive. However, on the contrary, priority can be set between each slave station using this phenomenon. That is, the access order may be set forward for a slave station having a short input signal transition cycle. In this way, there is a high possibility that an accurate input signal (change) of that slave station will be captured in one communication cycle, and an access has occurred due to an abnormality in communication with a slave station whose access order is later. The order will not adversely affect the input data update cycle from the previous slave station.
[0007]
【Example】
FIG. 1 is a flowchart for the first embodiment of the present invention and shows the communication control procedure of the master station. Each slave station is numbered n, and the master station repeats access to all eight slave stations from slave station 0 to slave station 7 in order. Here, the slave station number n is a number assigned by the master station for the purpose of controlling the communication order, and does not necessarily match the address of each slave station. Also, not only one number is set for one slave station, but if there is a slave station that is accessed multiple times in one communication cycle, a different number may be assigned for that number of times. is there. TXN indicates the number of times that retransmission has been performed for one slave station, and is a count value of a retransmission counter that is added each time retransmission is performed. TXC indicates the total number of retransmissions performed in one communication cycle, and is a count value of a total retransmission counter that is added each time retransmission is performed.
Note that the maximum number of retransmissions for one slave station can be set to a different value depending on the importance of the slave station, but in this embodiment, for ease of explanation, In contrast, the maximum is twice. If the maximum number of re-transmissions is performed for all the slave stations, 2 × 8 = 16 times in one communication cycle. However, in the present invention, a value smaller than 16 is given with a limitation. 5 is set as the upper limit value.
[0008]
First, in step S11, transmission is performed to the slave station n. In step S12 after the transmission is completed, a reception standby state is entered, and normal reception or abnormality detection of the slave station reply is performed. If normal reception is possible, the process proceeds to step S13, and if a communication abnormality is detected, the process proceeds to step S16.
In step S13 after normal reception, the retransmission counter TXN is cleared, the transmission destination slave station number n is incremented, the process returns to step S11, and access to the next slave station is started. When the number exceeds 7, it indicates that one communication cycle has been completed. In step S15, the slave station number n and the retransmission total counter TXC are cleared, and the access is repeated from the beginning of the communication cycle, that is, from the slave station 0. .
After the abnormality is detected, retransmission is performed to the same slave station. However, if it is determined in step S16 that the retransmission total counter TXC has reached the maximum value of 5, the process returns to step S13 without performing retransmission. Then, access to the next slave station is performed in the same way as during normal reception. Even if TXC <5, if it is determined in the next step S17 that the retransmission counter TXN for the child station has reached the maximum value of 2, the process proceeds to step S13 in the same manner. Only when TXN <2 and TXC <5, the process proceeds to step S18, and after incrementing TXN and TXC, the process proceeds to step S11. At this time, since the slave station number n is not incremented, retransmission is performed to the same slave station.
[0009]
FIG. 2 is a diagram showing an example of a specific operation of the present embodiment, showing the access order with each child station, and the values of the retransmission counter TXN and retransmission total counter TXC of the parent station. The numbers with circles indicate the numbers of the slave stations to be accessed, and the hatched portions indicate the access where the communication abnormality occurred. It is assumed that time elapses from left to right in the figure.
After a successful access 501 with the slave station 0, if a communication error occurs during the access 502 with the slave station 1, the master station increments the retransmission counter TXN and the retransmission total counter TXC, and again with the slave station 1. Access 503 is performed. When this access is normally performed, the retransmission counter TXN is cleared and the subsequent access 504 with the slave station 2 is performed. If an abnormality occurs during the access 505 with the slave station 3, the access 506 with the slave station 3 is performed again by the same processing as in the case of the slave station 1. However, if an abnormality occurs again, the same processing is performed again. The access 507 with the slave station 3 is repeated. However, even if a further abnormality occurs, the retransmission counter TXN indicates the upper limit of 2. Therefore, the retransmission counter TXN is cleared without accessing the slave station 3 again, and access 508 with the next slave station 4 is performed. Move on. Hereinafter, although the same operation is performed, if the re-access is performed twice in the access 509 to 511 with the slave station 5, the total retransmission counter TXC indicates the upper limit of 5 at this time. Therefore, as shown in the figure, even if an abnormality occurs while accessing the slave station 7 and access 513, the access to the next slave station is started without re-accessing. In the case shown in FIG. 2, since the communication cycle ends, the retransmission total counter is cleared and the access to the slave station 0 is returned.
With the above operation, according to the first embodiment, the time required for one communication cycle is always kept below Tmax.
[0010]
According to the first embodiment, as described above, the later the communication order, the higher the possibility that the retransmission total counter has already indicated that retransmission is not possible when an abnormality is detected. Using this, priority can be set for each slave station. In the example shown in FIG. 7, when priority is given to the slave stations 102 to 109, 1: the driver seat power seat actuator unit slave station 108, 2: the passenger seat power seat actuator unit slave station 109, 3: the driver seat Power station switch slave station, 4: passenger seat power seat switch slave station, 5: driver seat power window slave station 103, 6: passenger seat power window slave station, 7: right rear seat power window slave station 106 , 8: The left rear seat power window slave station 107 is arranged in this order.
If the slave station with a shorter transition cycle of the input signal is set to the front of the communication order, the possibility of capturing the input signal in one communication cycle becomes higher, and the occurrence of an abnormality in the communication with the slave station with the slower communication order is earlier in the communication order. There is no adverse effect on the input data update cycle from the slave station.
In the first embodiment, the number of retransmissions per communication cycle is limited to five. However, when the present invention is actually used, access to a slave station having an input signal with the shortest transition cycle is possible. The number of times should be set in consideration of the interval falling within a certain time.
[0011]
FIG. 3 is a flowchart for the second embodiment of the present invention. In the first embodiment, the total number of retransmissions per communication cycle is used as one of the retransmission conditions. During the cycle, the count value of the retransmission time counter that counts all the time required for access by re-transmission to any of the slave stations is used.
For this reason, the retransmission total counter TXC is not used as in the first embodiment. Instead, a re-access time counter TCNT that adds the time required for the access every time retransmission is installed is used. . The number of retransmissions for one slave station is uniformly set to a maximum of 2 times as in the case of the first embodiment.
Further, assuming that the time required for one access with each slave station is 10, and assuming that the maximum number of retransmissions is performed for all the slave stations, it is spent for access by retransmission within one communication cycle. The time is 2 × 8 × 10 = 160. In this embodiment, the time spent for access by this retransmission is limited. In this embodiment, the time that can be used for retransmission per communication cycle is set to 50, which is smaller than 160, as the upper limit. did.
[0012]
In FIG. 3, first, in step 21, transmission is performed to the slave station n. After the transmission is completed, a reception standby state is entered at step 22 to perform normal reception or abnormality detection of the slave station reply. If normal reception is possible, the process proceeds to step S23, and if a return communication abnormality is detected, the process proceeds to step S26.
In step 23 after normal reception, the retransmission counter TXN is cleared, the transmission destination slave station number n is incremented and the process returns to step 21 to move to the next slave station. Before that, however, the slave station number n is added in step S24. When the number exceeds 7, it indicates that one communication cycle is completed. In step S25, the slave station number n and the re-access time counter TCNT are cleared, and access is repeated from the beginning of the communication cycle, that is, slave station 0. It is.
After the abnormality is detected, the same slave station is retransmitted. If it is determined in step S26 that the reaccess time counter TCNT has reached 50 or more, the process proceeds to step S23 without performing retransmission. As with normal reception, access to the next slave station is performed. Even if TCNT <50, if it is determined in the next step S27 that the retransmission counter TXN for the child station has reached the maximum value of 2, the process proceeds to step 23 in the same manner. Only when TXN <2 and TCNT <50, the process proceeds to step S28, TXN is incremented, the access required time is added to TCNT, and then the process proceeds to step S21. At this time, since the slave station number n is not incremented, retransmission is performed to the same slave station.
[0013]
FIG. 4 shows an example of a specific operation of the second embodiment, except that the re-access time counter TCNT is used instead of the total retransmission counter TXC, and the first operation shown in FIG. Since the operation is similar to that of the embodiment, detailed description thereof is omitted.
In the operation example shown in FIG. 4, the number of retransmissions is limited by adding the access required time that is known in advance to the reaccess time counter TCNT. However, as shown in FIG. It is also possible to use a retransmission timer TIM that is measured every time a station is accessed. The operation is exactly the same as in FIG.
[0014]
In this second embodiment, the time that can be used for retransmission per communication cycle is set to 50. However, when the present invention is actually used, the access interval with the slave station having the shortest input signal of the transition cycle is set. It is better to set the time in consideration of being within a certain time.
[0015]
The second embodiment is the same as the first embodiment in that priority can be set for each slave station according to its communication order. However, the difference between the second embodiment and the first embodiment is that This becomes conspicuous when the data length of the data to be transmitted / received is different every time. For example, among the slave stations 0 to 7, considering that the slave stations 5 to 7 have a shorter transmission / reception data length than the other slave stations, and the time required for access is only half, 5, FIG. Assume that a communication error has occurred as shown in FIG. FIG. 6 shows a comparison of operations in each embodiment.
In the case of the first embodiment, as shown in FIG. 6A, when an abnormality is detected in the reply from the slave station 7, the retransmission total counter TXC already indicates the maximum value of 5. Since transmission is not performed and the access to the slave station 0 is started, the load drive response to the input from the slave station 7 deteriorates.
On the other hand, in the second embodiment, as shown in FIG. 6B, the value of the re-access time counter TCNT when an abnormality is detected in the reply from the slave station 7 is 40, which is still the maximum value of 50. Therefore, retransmission to the slave station 7 can be performed. Considering the purpose of increasing the number of retransmissions and keeping the time required for one communication cycle to a certain time, when there are slave stations that exchange data with different data lengths, the time is reduced as in the second embodiment. It can be said that the method of limiting the number of retransmissions used can retransmit by effectively utilizing the permitted time limit.
[0016]
【The invention's effect】
As described above, according to the present invention, not only the number of retransmissions from the master station to each slave station is limited, but also the total number of retransmissions per communication cycle or the total time used for retransmissions. By providing a restriction, priority can be set for the order of communication with each slave station, and the input data update cycle with a slave station with a high priority will adversely affect communication abnormalities with slave stations with a low priority. It is possible to obtain an effect that accurate control is possible as a whole system. In particular, according to the method of setting a limit on the total time used for retransmission, when slave stations with different transmission / reception data lengths are mixed, there is an effect that retransmission can be executed efficiently with respect to the limit on the number of retransmissions.
[Brief description of the drawings]
FIG. 1 is a flowchart for a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a specific operation example of the first embodiment of the present invention;
FIG. 3 is a flowchart for a second embodiment of the present invention.
FIG. 4 is a diagram for explaining a specific operation example of the second embodiment of the present invention.
5 illustrates an example of operation using a retransmission timer TIM instead of using the re-access time counter TCNT as in the example of operation shown in FIG. 4 for monitoring the access required time in the second embodiment of the present invention. FIG.
FIG. 6 shows that when slave stations with different transmission / reception data lengths are mixed, the second embodiment that limits the number of retransmissions using time is more limited than the first embodiment that simply limits the number of retransmissions. FIG. 6A is a diagram for specifically explaining that the time can be effectively used, with FIG. 6A showing an operation example of the first embodiment and FIG. 6B showing an operation example of the second embodiment.
FIG. 7 is a diagram illustrating an example of vehicle electrical equipment using a multiplex communication system.
FIG. 8 is a diagram showing a specific example of a communication waveform and its format when a multiple communication system is applied to vehicle electrical equipment.
FIG. 9 is a diagram illustrating an example of a communication procedure when a multiple communication system is applied to vehicle electrical equipment.
[Explanation of symbols]
TXN: Number of times of retransmission from the master station to the specific slave station TXC: Total number of retransmissions to the slave station during one communication cycle TCNT: Access by retransmission to the slave station during one communication cycle Total time required for 101 ... Master station 102 ... Driver seat power seat switch slave station 103 ... Driver seat door slave station 104 ... Passenger seat power seat switch slave station 105 ... Passenger seat door slave station 106 ... Rear right seat door slave station 107 ... rear left seat door slave station 108 ... driver seat power seat slave station 109 ... passenger seat power seat slave station 121, 122 ... power seat switch 123-126 ... power window switch 127-130 ... door lock detection switch 131-134 ... power Wind motors 135 to 138... Door lock motor 139... Seat position sensor switches 140 and 141. 2 ... Communication line 143 ... Driver seat door 144 ... Passenger seat door 145 ... Rear right seat door 146 ... Rear left seat door 147 ... Driver seat power seat 148 ... Passenger seat power seat 201 ... Communication start code 202 ... Command frame 203 ... Address Frame 204 ... Data frame 1
205 ... Data frame 2 206 ... Communication end code 207 ... Parity bit 208 for command frame and address frame ... Parity bit 209 for data frame 1 ... Parity bits 301 to 304 for data frame 2 ... Transmission of parent station 305 to 308 ... Child station 501, 514, 701, 714, 801, 814, 901, 914, 915, 929... Access with child station 0 502, 503, 702, 703, 802, 803, 902, 903, 916, 917. 1, access 504, 704, 804, 904, 918 ... access to child station 2 505 to 507, 705 to 707, 805 to 807, 905 to 907, 919 to 921 ... access to child station 3 508, 708, 808, 908, 922 ... access 5 with the slave station 4 9 to 511, 709 to 711, 809 to 811, 909 to 911, 923 to 925 ... access to the slave station 5 512, 712, 812, 912, 926 ... access to the slave station 6 513, 713, 813, 913, 927, 928 ... Access with the slave station 7

Claims (2)

One master station and a plurality of slave stations are connected by a multiplex communication line, the master station first transmits to one slave station, and then receives the reply from the slave station that received this, the access operation, In a multiplex communication method that sequentially performs each slave station in accordance with a predetermined access order and repeats a certain pattern of this access order as one communication cycle,
When the master station successfully receives the reply from the slave station, the master station moves to the access operation to the next slave station according to the access order. If is established, re-send to the same slave station, and if the retransmission condition is not established, move to the access operation with the next slave station according to the above access sequence,
The master station includes a retransmission counter that counts the number of retransmissions for each slave station in the one communication cycle, and a retransmission total that counts the total number of retransmissions to each slave station in the one communication cycle. If the count value of the retransmission counter is equal to or less than a specific value predetermined for each slave station and the count value of the total retransmission counter is equal to or less than a predetermined value, the retransmission condition is A multiplex communication method characterized by being established. One master station and a plurality of slave stations are connected by a multiplex communication line, the master station first transmits to one slave station, and then receives the reply from the slave station that received this, the access operation, In a multiplex communication method that sequentially performs each slave station in accordance with a predetermined access order and repeats a certain pattern of this access order as one communication cycle,
When the master station successfully receives the reply from the slave station, the master station moves to the access operation to the next slave station according to the access order. If is established, re-send to the same slave station, and if the retransmission condition is not established, move to the access operation with the next slave station according to the above access sequence,
The master station counts the retransmission counter for counting the number of retransmissions for each slave station during the one communication cycle, and the time required for access by retransmission to each of the slave stations during the one communication cycle. If the count value of the retransmission counter is equal to or less than a specific value predetermined for each slave station and the count value of the retransmission time counter is also equal to or less than a predetermined value, the retransmission time counter is set. A multiplex communication method characterized in that a transmission condition is satisfied.

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