JPH09128019A - Remote i/o system for plc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the superposition of IN data received from respective IN slaves and to surely receive the IN data. SOLUTION: At the time of receiving OUT data frame OF from a remote master by batch transmitting/receiving method, respective IN slaves transmit IN data frames IF0 to IF2 to the remote master at each timing of reference idle time in which frames are not mutually superposed by considering frame length and physical delay. The remote master receives the IN data frames IF0 to IF2 with the time slot of each slave based upon the basic idle time and enters respective IN data IN0 to IN2 based upon start bits to be the headers of respective data frames IF0 to IF2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a remote master and a plurality of slaves connected to the remote master via a communication cable, and collectively transmits and receives IN data and OUT data between the remote master and each slave. The present invention relates to a remote I / O system of a programmable controller (hereinafter, referred to as "PLC") that transmits and receives by a method.

[0002]

2. Description of the Related Art In a PLC remote I / O system,
There is a so-called batch transmission / reception method as a method of transmitting and receiving IN data and OUT data between a remote master and each slave connected to the remote master via a communication cable.

In the batch transmission / reception system, as shown in FIG.
In the transmission and reception of OUT data from the remote master to the OUT slave, the remote master collectively transmits the OUT data frame OF in which the header of the OUT data is attached to all the slaves, while each OUT slave transmits the OUT data frame OF at the timing of each node. The OUT data addressed to the own node is received from the OUT data frame OF.

On the other hand, when transmitting and receiving IN data from the IN slave to the remote master, each IN slave outputs OUT.
While the IN data frame IF including the IN data is transmitted at the timing of each node with reference to the time of receiving the data frame OF, the remote master transmits the IN data frame I
Each IN in the order of the node address of each IN slave from F
Receive IN data from slave.

[0005]

By the way, in such a PLC remote I / O system, it is usually desired to perform high-speed I / O data processing, that is, IN data input, PLC main body processing, and OUT data output. There is also a request to collect the management information such as the status of each slave and the communication status, and to ensure the reliability because the remote I / O system is constructed.

However, in the conventional batch transmission / reception method described above, after the remote master batch-transmits OUT data frames to the slaves, each IN slave continuously transmits each IN data frame and the remote master receives it. Therefore, due to physical delay such as delay due to transceiver, communication cable, transmission / reception processing, IN
There is a problem that IN frames cannot be received because the data frames overlap each other.

That is, as shown in FIG. 7, due to the physical delay, the reception timing of the IN data 2 from the IN slave 2 in the remote master is delayed from the sampling point, and the IN data frame 3 from the next IN slave 3 is received. And IN data 2 and 3 may not be received.

In the conventional batch transmission / reception method described above, since only IN and OUT data is transmitted / received between the remote master and the slave, there is a problem that the reliability of the network cannot be secured by collecting the management information. It was

Therefore, when the slave sends notification of management information to the remote master by the batch transmission / reception method, the data bit for IN data transmitted by the IN slave must be used. In this case, the IN data bit is transmitted. Consumption reduces the number of I / O points that can be used by the application program on the remote master side, and causes a new problem that the OUT slave must be added with a function of transmitting management information to the IN slave. It will be.

Therefore, the present invention has been made in view of such a problem, and prevents the IN data frames from the IN slaves from overlapping with each other and can reliably receive the IN data from the IN slaves. An object of the present invention is to provide a PLC remote I / O system in which the management information from each slave is collected without lowering the transmission efficiency and the reliability is improved.

[0011]

In order to achieve the above object, the invention according to claim 1 comprises a remote master and a plurality of IN slaves and OUT slaves connected to the remote master via a communication cable. In a PLC remote I / O system in which IN data and OUT data are transmitted and received between the remote master and each slave by a batch transmission / reception method, regarding transmission / reception of OUT data, the remote master outputs OUT to each slave. Sends data in batch and outputs each OUT
While the slave receives OUT data at the timing of its own node, each IN slave transmits / receives IN data to the remote master at every basic idle time after considering the frame length and physical delay after receiving the OUT data. The remote master transmits the IN data with the start code, while the remote master sends the IN data from each IN slave in the time slot of each IN slave based on the basic idle time based on the start code attached to each IN data. Receiving data.

According to a second aspect of the present invention, the remote master includes a plurality of IN slaves and OUT slaves connected to the remote master via a communication cable, and the IN is provided between the remote master and each slave.
In a PLC remote I / O system in which data and OUT data are transmitted / received in a batch transmission / reception method, regarding transmission / reception of OUT data, the remote master transmits OUT data to each slave in a batch and each OUT slave transmits OUT at the timing of its own node
While receiving data, each IN slave sends and receives IN data after receiving the OUT data, by assigning its own node address to the remote master every basic idle time in consideration of the frame length and the physical delay. While transmitting IN data, the remote master receives IN data from each IN slave based on the node address attached to each IN data.

According to a third aspect of the present invention, in the PLC remote I / O system according to the first or second aspect, the basic idle time is a frame length of IN data,
It is a sum of the difference between the maximum physical delay and the minimum physical delay of the IN slave.

According to a fourth aspect of the present invention, in the PLC remote I / O system according to the first, second or third aspect, the remote master outputs O to each slave.
After transmitting the UT data all at once, while transmitting the IN data transmission start command, each IN slave transmits each IN data to the remote master every basic idle time based on the time of receiving the IN data transmission start command. , Is characterized.

According to a fifth aspect of the present invention, in the PLC remote I / O system according to the first, second, third or fourth aspect, the remote master collectively outputs OUT data to each slave. At the time of transmission, while transmitting a management information request designating the address of a specific slave, the specific slave whose address is designated by the management information request immediately receives the OUT data and the management information request. It is characterized in that the remote master transmits management information and receives the management information from a specific slave having the specified address before receiving the IN data from each IN slave.

According to a sixth aspect of the present invention, in the PLC remote I / O system according to the fifth aspect, the remote master specifies the address of a specific slave specified in the management information request for each next slave. The feature is that the address is updated.

For this reason, in the present invention, when transmitting / receiving IN data, each IN slave receives a start code or a node from the remote master after receiving the OUT data at each basic idle time in consideration of the frame length and the physical delay. Each IN data is sent with an address.

Then, the remote master receives IN data from each IN slave in the time slot for each IN slave based on the basic idle time based on the start code attached to each IN data. IN data does not overlap due to physical delay such as.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Each embodiment of a PLC remote I / O system according to the present invention will be described below.

FIG. 1 shows a PLC remote I according to the present invention.
1 shows a configuration of a first embodiment of an / O system.

The remote I / O system of this PLC is
As shown in the figure, one PLC main body 1 and a plurality of remote slaves 2 to 7 (6 for convenience) are connected via a serial I / F communication cable 8. There is.

The PLC main body 1 is equipped with a master unit 11 which is a remote master connected to the communication cable 8 and a CPU unit 12 which executes user program processing. It is equipped with an I / O unit that is connected to output devices, and is connected by parallel I / F.

Each of the remote slaves 2 to 7 is connected to a switch, a sensor or the like, and is connected to IN slaves 2, 4 and 6 for fetching IN data from them, a relay or a valve, and outputs OUT data to them. The OUT slaves 3, 5, and 7 are connected.

The slave addresses # 0 to 2 are assigned to the IN slaves 2, 4 and 6 as node addresses, and IN0 to IN2 are transmitted to the PLC main body 1 as IN data, while the OUT slaves 3 and 5 are transmitted. , 7 are given slave addresses # 3 to 5, respectively.

FIG. 2 shows the PLC according to the first embodiment.
The OUT data and IN data which the master unit 11 of the main body 1 transmits / receives to / from each slave 2 to 7 and the transmission / reception timing thereof are shown.

In FIG. 2, the OUT data frame OF is transmitted collectively by the master unit 11 to the IN and OUT slaves 2 to 7, and includes a header and
It is composed of OUT data to OUT slaves 3, 5, and 7.

In addition, IN data frames IF0 to IF2
Are transmitted by the IN slaves 2, 4, and 6, respectively. At the beginning of each IN data 0 to 2, each IN data 0 to
A header, which is a start code indicating the reading timing of 2, is attached.

Further, in the figure, AO, A1, A2 ...
After the master unit 11 completes the transmission of the OUT data frame OF, the slave addresses # 0 to 2 are transmitted.
It shows the time until the IN data is received from the IN slaves 2, 4, and 6, and is generally as follows. AO (incoming timing of IN data frame from IN slave 2) = physical delay from IN slave 2 + basic idle time x 0 = physical delay from IN slave 2

Here, the "basic idle time" means each I
IN data frame IF in N slaves 2, 4 and 6
A time that is the base of the transmission timing of 0 to IF2 and is set so that the IN data frames do not overlap when the master unit 11 receives the IN data frames IF0 to IF2 from the IN slaves 2, 4, and 6. Is.

A concrete example of the basic idle time will be explained. For example, the frame length of the IN data frames IF0 to IF2 and the longest IN slave, that is, the distance from the master unit 11 in FIG. From the physical delay of the IN slave 6 having the maximum dynamic delay to the shortest IN slave, that is, the master unit 1 in FIG.
It is the addition result with the result of subtracting the physical delay of the IN slave 2 having the smallest distance from 1 and the minimum physical delay due to the communication cable 8 or the like, and is expressed by the following formula. Basic idle time = frame length + (longest slave physical delay-shortest slave physical delay).

In this embodiment, the physical delay is described as being large in proportion to the communication cable 8 and the like. However, if the physical delay is influenced by a factor other than the communication cable 8, communication will be performed. Factors other than the cable 8 should be taken into consideration.

In FIG. 2, A1 and A2 are A1 (incoming timing of IN data frame from IN slave 3) = physical delay from IN slave 3 + basic idle time × 1 A2 (from IN slave 4) IN data frame arrival timing) = physical delay from IN slave 4 + basic idle time x 2

For this reason, each I from the adjacent IN slaves 2, 4 and 6 which is continuously received by the master unit 11 is transmitted.
Time difference between the N data frames IF0 to IF2, specifically, the difference between A0 and A1 or the difference between A1 and A
The difference from 2 is larger than the basic idle time, and at least larger than the IN data frame length, so that there is no frame overlap when the master unit 11 receives the IN data frame.

Further, the master unit 11 sends IN data frames IF0 to IF2 from the IN slaves 2, 4, and 6 respectively.
The IN0 to IN2 time slots, which are monitoring time slots for receiving each IN from each node, include the above basic idle time and each IN from the adjacent IN slaves 2, 4, and 6.
It is desirable to set the value or a value around the value based on the added value with the time difference between the data frames IF0 to IF2.

Next, the operation of the first embodiment thus constructed will be described mainly with reference to FIG.

First, OUT data is transmitted from the master unit 11 to the OUT slaves 3, 5, and 7 by a batch transmission method as shown in FIG. 2, and the OUT data frame OF carrying the OUT data is transmitted to all slaves. Send to 2-7.

OU receiving the OUT data frame OF
Since the T slaves 3, 5, and 7 have OUT data to be received by their own node in this frame OF, they start counting based on the header in this frame OF, and
The OUT data is received at the timing of its own node.

Further, the IN slaves 2, 4 and 6 that have received this OUT data frame OF do not receive data from this OUT data frame OF, and
After receiving the data frame OF, the timer is run to transmit the IN data frames IF0 to IF2 at each idle time (= basic idle time × slave address).

Therefore, the transmitted IN data frames IF0 to IF2 are transmitted at intervals of the basic idle time, so that when the master unit 11 receives the IN data frames IF0 to IF2. ,
The IN data frames do not overlap each other.

By the way, in the master unit 11, the OU
After the transmission of the T data frame OF, a timer is run to determine whether or not the IN data frames F0 to F2 come from the IN slaves 2, 4 and 6 in the IN0 to IN2 time slots of the IN slaves 2, 4 and 6, respectively. If each IN data frame F0 to F2 is coming in each time slot, it is counted based on the start bit which is the header, and each IN0 to IN2 following the header is taken in. To

At this time, the IN0 to IN2 time slots are set based on the basic idle time set so that the IN data frames do not overlap each other, and each I slot
Since there is a margin for the N data frame length, the master unit 11 can absorb the physical delay due to the communication cable 8 and the like, and can reliably receive IN data from each IN slave.

Therefore, according to this first embodiment, each I
From the N slaves 2, 4, and 6, IN data frames F0 to F2 are transmitted at intervals of the basic idle time set so that the IN data frames do not overlap each other, and the monitoring time slot for each slave is also provided. Since the master unit 11 is set based on the basic idle time and the like, the IN unit of the IN data frames IF0 to I
When F2 is received, the frames do not overlap each other, and it becomes possible to reliably capture each IN0 to IN2 based on the headers in the IN data frames F0 to F2.

Therefore, according to the first embodiment, the IN due to the physical delay of the transceiver, the communication cable, etc.
The reliability is improved because the data cannot be received.

In the first embodiment, since IN data can be continuously received without transmitting a command to each IN slave, physical delay and IN
By adjusting the idle time of IN data frame transmission in each slave and the time slot for IN data frame reception in the remote master according to the data frame length, the transmission speed can be increased.

In the first embodiment, the frame transmission rate between the remote master and the slave, the idle time, the method and means for setting the time slot, etc. were not described, but the present invention does not. , The master unit 11 and each of the slaves 2 to 7 are provided with a transmission speed changeover switch, an idle time changeover switch, and a time slot changeover switch to construct a PLC remote I / O system with a variable transmission speed. You can

In the first embodiment, it has been described that each IN slave runs the timer based on the reception timing of the OUT data frame from the master unit 11 and each node transmits each IN data.
According to the present invention, the master unit 11 receives the IN data transmission start command by transmitting the IN data transmission start command after the transmission of the OUT data frame, not based on the reception timing of the OUT data frame. After that, each IN slave may start the transmission process of the IN data frame.

In this case, the OU having a long data length
Even if a T data frame causes a reception error in an IN slave due to noise or the like, the IN slave does not receive the I data based on the IN data transmission start command frame.
N data can be transmitted.

Therefore, according to this method, the OUT data transmission / reception processing and the IN data transmission / reception processing are independent, and the probability that the I / O data exchange cycle becomes long due to noise or the like can be reduced. .

Next, the PLC remote I / O according to the present invention will be described.
A second embodiment of the O system will be described.

The second embodiment has the same system configuration as that of the first embodiment shown in FIG. 1 and is different from the first embodiment in that the master unit 11 is provided with an IN data frame from each IN slave. The feature is that the slave address of each slave is provided in the header in the IN data frame transmitted by each IN slave without providing the monitoring time slot for receiving.

FIG. 3 shows OUT data and IN data transmitted / received by the master unit 11 in the second embodiment, and transmission / reception timing thereof.

As shown in the figure, the master unit 11 is
Same OUT data frame OF 'as in the first embodiment
After the transmission of, the IN data frames IF'0 to IF'2 with the slave address of each slave as a header are received from the IN slaves 2, 4, and 6, but not in the node monitoring time slot. Based on the slave address of each slave, the source slaves of the IN data frames IF'0 to IF'2 are determined and received.

Therefore, according to the second embodiment, since the slave address of each slave is set as the header, there is a drawback that the IN data frame length becomes long and the cycle time becomes slow, but that much. Since it is not necessary to register the monitoring time slot for each slave in the master unit 11 in advance, it is possible to easily and easily prevent the IN data from overlapping due to physical delay and improve the reliability.

In the second embodiment, like the first embodiment, each IN slave transmits each IN data based on the reception of the OUT data frame from the master unit 11. As described above, according to the present invention, the master unit 11 transmits the IN data transmission start command frame after transmitting the OUT data frame, and after receiving this command, it is not based on the reception of the OUT data frame. The IN slave may start the IN data frame transmission process.

Next, the PLC remote I / O according to the present invention will be described.
A third embodiment of the O system will be described.

The third embodiment is an improvement of the first embodiment and the second embodiment, and the management information in the master unit 11 which can be executed only by the method of using the IN bit in the batch transmission / reception system up to now. The collection of
The feature is that it is possible without using N bits.

Since the third embodiment has the same system configuration as that of the first embodiment shown in FIG. 1 like the second embodiment, the master unit 11 in the third embodiment transmits and receives. The features of the third embodiment will be described with reference to OUT data, IN data, and transmission / reception timing.

FIG. 4 shows OUT data and IN data transmitted / received by the master unit 11 in the third embodiment, and transmission / reception timing thereof.

In the third embodiment, unlike the frame transmission / reception of the first embodiment shown in FIG. 2 and the frame transmission / reception of the second embodiment shown in FIG. 3, the master unit 11 collectively transmits to each slave. In addition to the header and the OUT data to the OUT slave, the OUT data frame OF ″ is added with a slave address as a management information request for requesting management information (status) response to each of the IN and OUT slaves, Moreover, it is characterized in that the slave address is updated every communication cycle.

Incidentally, without updating the slave address,
You may make it specify only the slave address of a specific slave. In FIG. 4, I of slave address # 1
The address "address # 1" of the N slave 4 is designated.

In the figure, frames IF "0 to IF" 2
Is an IN slave with slave addresses # 0 to 2, 2, 4,
6 shows a frame of IN data to be transmitted, and the point that a start code or a slave address indicating the fetching timing of each IN data is added as a header to the beginning of each IN data is the first embodiment shown in FIG. The form is the same as that of the second embodiment shown in FIG. 3, but in each IN slave, the IN data is delayed by the transmission timing of the management information frame transmitted by the slave whose slave address is specified as the management information request. The frames IF ″ 0 to IF ″ 2 are transmitted.

The frame SF is the IN slave 4 of the slave address # 1 whose slave address is designated by "address # 1" in the OUT data frame OF ".
Shows that the IN slave 4 having the slave address # 1 transmits the management information frame SF immediately after receiving the OUT data frame OF ″ from the master unit 11.

In FIG. 4, as in the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 3, the IN data frames IF ″ 0 to IF ″ 2 in the master unit 11 are shown.
Although the reception timing and the monitoring time slot are not shown in the figure, the third embodiment is an improvement of the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. I just omitted it.

Next, the operation of the third embodiment thus constructed will be described. First, the master unit 11
However, the OUT data frame OF ″ in which the slave address as the management information request is set after the OUT data is transmitted to all the slaves by the batch transmission method.

OU receiving the OUT data frame OF
The T slave starts counting from the header in the OUT data frame OF and receives the OUT data at the timing of its own node, while the OUT data frame OF is received.
In each IN slave that has received the IN data, the idle time (= management information transmission time + basic idle time × slave address), which is an extra management information transmission time, is opened unlike the first embodiment and the like, and the IN data is opened. Send the frame.

At this time, since the "address # 1" is set in the OUT data frame OF ", the IN slave 4 having the slave address # 1 receives the OUT data frame OF" from the master unit 11 and immediately receives the message. As shown in (1), the management information frame SF in the IN slave including the header and the status (management information) is transmitted, and then the IN data frame of the own node is transmitted.

Then, the master unit 11 can receive the management information frame SF from the IN slave having the slave address # 1 before receiving the IN data frames IF0 to IF2 from the IN slave.

When the above process is carried out for all the cycles of all the nodes, that is, for all the slaves 2 to 7 of IN and OUT, the master unit 11 outputs the OUT data frame O.
Since the slave address added to F ″ has been updated for all the slaves 2 to 7, the management information of all the slaves 2 to 7 can be collected.

Therefore, according to the third embodiment, management information is collected from one slave in each communication cycle, and the slave address is updated in each communication cycle, so that all slaves can be processed in several cycles of all nodes. Since the management information can be collected, the reliability of the remote I / O system can be ensured without significantly reducing the communication cycle.

Further, by not updating the slave address or by changing the method of updating, it becomes possible to collect the management information of only a specific slave or an arbitrary slave.

In the first to third embodiments described above, the remote I / O in which the master unit 11 as the remote master is mounted on the PLC main body 1 shown in FIG.
Although described with reference to the system, in the present invention, as shown in FIG. 5, the PLC main body 11 'includes a master unit 11'.
Without installing, the master unit 11 'is connected to the I / O unit 13 mounted on the PLC main body 1'by a parallel I / F, and the serial I / F communication cable 8 is connected to the remote master unit 11'. You may make it connect various slaves via.

[0072]

As described above, according to the present invention, each IN
Since the IN data frame is transmitted from the slave to the remote master at each idle time in consideration of the physical delay, when the remote master receives the IN data frame, the frames do not overlap each other and the IN data frame does not overlap. It becomes possible to capture each IN data based on the header in the frame.

Therefore, according to the present invention, since the IN data cannot be received due to a physical delay such as a transceiver, a communication cable, and a delay due to transmission / reception processing, reliability is improved and each IN slave is improved. Since IN data can be received continuously without sending a command every time, the transmission speed can be increased by adjusting the idle time and time slot according to the physical delay and the frame length. Become.

Further, according to the present invention, the slave address for requesting the management information is added to the OUT data frame and transmitted, and the slave address is updated every communication cycle. The slave management information can be collected, and the reliability of the remote I / O system can be ensured without significantly reducing the communication cycle.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a first embodiment of a PLC remote I / O system according to the present invention.

FIG. 2 is an explanatory diagram showing OUT data and IN data transmitted / received by a remote master in the first embodiment, and transmission / reception timing thereof.

FIG. 3 is an explanatory diagram showing OUT data and IN data transmitted / received by a remote master and a transmission / reception timing thereof in the second embodiment.

FIG. 4 is an explanatory diagram showing OUT data and IN data transmitted / received by a remote master in the third embodiment, and transmission / reception timing thereof.

FIG. 5 is a configuration diagram showing another configuration of the PLC remote I / O system according to the present invention.

FIG. 6 is an explanatory diagram showing OUT data and IN data transmitted / received by a remote master and transmission / reception timing thereof in the related art.

FIG. 7 is an explanatory diagram showing a problem of the conventional technique.

[Explanation of reference symbols] 1 PLC main body 11 Master unit (remote master) 12 CPU unit 13 I / O unit 11 'Master unit (remote master) 2, 4, 6 IN slave 3, 5, 7 OUT slave 8 Communication cable OF OUT Data frame OF ′ OUT data frame OF ″ OUT data frame IF0 to IF2 IN data frame IF′0 to IF′2 IN data frame IF ″ 0 to IF ″ 2 IN data frame SF management information frame

Claims (6)

[Claims] 1. A remote master and a plurality of IN slaves and OUT slaves connected to the remote master via a communication cable, and collectively transmits and receives IN data and OUT data between the remote master and each slave. In the remote I / O system of PLC that is configured to perform transmission / reception by the method, for transmission / reception of OUT data, the remote master transmits OUT data to each slave all at once, and each OUT slave transmits OUT data at its own node timing. On the other hand, for IN data transmission / reception, after each IN slave receives the OUT data, each IN slave attaches a start code to the remote master at each basic idle time in consideration of the frame length and the physical delay. While the remote master is on Each IN slave each time slot based on the basic idle time,
A remote I / O system for a PLC, characterized in that it receives IN data from each IN slave based on the start code attached to each IN data. 2. A remote master and a plurality of IN slaves and OUT slaves connected to the remote master via a communication cable, and collectively transmits and receives IN data and OUT data between the remote master and each slave. In the remote I / O system of PLC that is configured to perform transmission / reception by the method, for transmission / reception of OUT data, the remote master transmits OUT data to each slave all at once, and each OUT slave transmits OUT data at its own node timing. On the other hand, for IN data transmission / reception, after receiving the OUT data, each IN slave attaches its own node address to the remote master at each basic idle time in consideration of the frame length and the physical delay.
A remote I / O system of PLC, wherein while transmitting data, the remote master receives IN data from each IN slave based on the node address attached to each IN data. 3. The basic idle time is an addition value of a frame length of IN data and a difference between a maximum physical delay and a minimum physical delay of the IN slave. The PLC according to claim 2.
Remote I / O system. 4. The remote master sends O to each slave.
After transmitting the UT data in a batch, while transmitting the IN data transmission start command, each IN slave transmits each IN data to the remote master every basic idle time based on the time of receiving the IN data transmission start command. The remote I / O system of PLC according to claim 1, 2 or 3, characterized in that. 5. The remote master sends O to each slave.
When transmitting the UT data in a batch, while sending the management information request specifying the address of the specific slave, the specific slave whose address is specified by the management information request is , The management information of the slave is immediately transmitted, and the remote master receives the management information from a specific slave that specifies the address before receiving the IN data from each IN slave. The PLC remote I / O system according to claim 1, claim 2, claim 3, or claim 4. 6. The remote I / C of PLC according to claim 5, wherein the remote master updates the address of the specific slave specified in the management information request to the address of the next slave in every communication cycle.
O system.