JP2001285318A - Data communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a management of existence of slave stations by a master station. SOLUTION: In this system, communication is processed between the master station and the slave stations. A priority signal slots PR1-PR4 are predetermined as informing timing from plural slave stations to the master station. These slots are assigned in advance to different timings for each plural slave stations. At notifying of notify signals at one time from the master station to the slave stations to establish communication frame synchronize, each slave stations receive the notify signals and response to the master station through their own priority request signal slots. The slave stations, even though there is no need of establishment of communication to the master station, transmit signals to make certain of existence rights as responses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data communication system in which a master station communicates with a plurality of slave stations.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 6-188892.
In the data communication system described in the publication, there are a master station and a plurality of slave stations performing data communication with the master station. In this communication system, when the master station transmits a predetermined signal to the slave station, the slave station transmits a response signal to the master station. At this time, if the slave station has no data to send to the master station, the slave station:
Nothing was sent to the master station. That is, the master station does not receive any response unless the slave station itself transmits some data to the master station. For this reason, when the master station does not receive a response signal from a certain slave station within a predetermined time, the master station transmits a predetermined signal to the next slave station. Further, the master station skips the slave station that has not received a response from the next time and requests the next slave station to transmit data. Hereinafter, the related art will be described more specifically with reference to FIGS.

FIG. 1 shows a conventional data communication system. This data communication system has a master station 30 and a slave station 32. The master station 30 transmits a notification signal 36 to the slave station 32, and the slave station 32 transmits a response 34 of the notification signal 36 to the master station 30. The same applies to other slave stations. There are a plurality of slave stations.

FIG. 2 shows an example of a communication frame used in the data communication system shown in FIG. The communication frame has a broadcast signal slot, a reception confirmation signal slot, a request signal slot, a permission signal slot, and a data signal slot. Data communication is performed in units of communication frames.
This is performed by transmitting and receiving one or more communication frames. In addition, the master station and the slave station can know the position of each signal slot by measuring the offset time from the broadcast signal. Hereinafter, how each signal in the communication frame is used will be described.

[0005] The broadcast signal is transmitted from the master station to the slave station using the broadcast signal slot B. The broadcast signal slot B is
It has a guard time 10, a burst header 12, and a Bch 14. The broadcast signal is sequentially transmitted from the master station to the slave station, and is used as a trigger for establishing frame synchronization of the slave station and for granting permission to start communication.

The acknowledgment signal is received acknowledgment signal slot A
It is transmitted from the master station to the slave station or from the slave station to the master station using 1 to A4. The reception confirmation signal slot A1 has a guard time 10, a burst header 12, and Ach16. Similarly, the acknowledgment signal slots A2, A3, and A4 also have a guard time and a burst header.

[0007] When data is generated from the master station to the slave station, the slave station receiving the data transmits a reception confirmation signal to the master station. When data is generated from the slave station to the master station, the master station receiving the data transmits a reception confirmation signal to the slave station. Therefore, the data transmission source (master station or slave station) receives the acknowledgment signal from the transmission destination (master station or slave station), so that the transmission data reaches the transmission destination (master station or slave station). Can be confirmed.

The request signal includes request signal slots R1 to R1.
2 is transmitted from the slave station to the master station. The request signal slot R1 includes a guard time 10, a burst header 12,
It has Rch18. Request signal slots R2 to R12
Also have a guard time and a burst header. When data to be transmitted from the slave station to the master station occurs,
The slave station transmits a request signal to the master station. As a general usage of the request signal, the slave station randomly selects the request signal slots R1 to R12 so as not to overlap request signal slots from other slave stations under the same master station, and A data transmission request to.

The permission signal includes permission signal slots G1 to G4.
Is transmitted from the master station to the slave station using. The permission signal slot G1 includes a guard time 10, a burst header 12, a G
ch20. The permission signal slots G2 to G4 also have a guard time and a burst header. The permission signal is transmitted from the master station to the slave station. The master station transmits a permission signal to the slave station as a master station permission response to the request signal slots R1 to R12 from the slave station. Also, when data to be transmitted from the master station to the slave station occurs, a permission signal is transmitted from the master station to the slave station.

The data signal is transmitted from the master station to the slave station or from the slave station to the master station using the data signal slot. The data signal slot (short) DS1 has a guard time 10, a burst header 12, and a DSch 22. Similarly, the data signal slots DS2 and DS3 have a guard time and a burst header. The data signal slot (long) D
L4 is guard time 10, burst header 12, DL
ch (12240) 24. For example, when the slave station transmits data to the master station, the slave station transmits a request signal to the master station. The master station transmits a permission signal to the slave station in response to a request signal from the slave station. The slave stations that are allowed to send data
The data is transmitted to the master station using the data signal slot.
Here, when the data to be transmitted is short, the data signal slots DS1 to DS3 are used, and when the data to be transmitted is long, the data signal slot DL4 is used. The same applies to the case where the master station transmits data to the slave station. The above is the role of each signal slot.

Next, the correspondence between the numbers in each signal slot will be described. Acknowledgment signal slots A1 to A4, permission signal slots G1 to G4, data signal slot DS1
The numbers DS3 and DL4 correspond to each other. For example, when transmitting data from the slave station to the master station, the master station transmits a permission signal to the slave station. At this time, if the master station uses the permission signal slot G1 (20), the slave station receiving the permission signal transmits data to the master station using the data signal slot DS1 (22). The master station that has received the data transmits a reception confirmation signal to the slave station using the reception confirmation signal slot A1 (16). Since the reception confirmation signal, the permission signal, and the data signal include a plurality of slots (the reception confirmation signal slot is A1 to A4, the permission signal slot is G1 to G4, and the data signal slots are DS1 to DS3 and DL4), And a plurality of slave stations can perform data communication.

FIG. 3 is a diagram showing a flow in which request signal slots R1 to R12 in the communication frame of FIG. 2 are processed on the master station side.

First, the master station checks whether all request signal slots R1 to R12 sent from the slave station have been processed (step S100). If the processing has been completed, the processing ends (step 122). Here, the nth request signal slot is referred to as a request signal slot Rn (n = 1 to 12). In step S100, the request signal slots R1 to R12
If not all have been processed, the following processing is repeated.

If there is no transmission request in the request signal slot Rn (step S102), the flow returns to step S100, and n
= N + 1 and the processing of the next request signal proceeds. If there is a transmission request in the request signal slot Rn (step S10
2) Distinguishing the length of transmission data (step S10)
4). Depending on the length of the data, the data signal slot DS
1 to select the use of DS3 or DL4 (step S1
04). When the data length is short, the data signal slots DS1 to DS3 are used, and when the data length is long, the data signal slot DL4 is used. If the transmission data is short, it is sequentially checked whether or not the data transmission slots DS1 to DS3 are in use (step S106,
S108, S110). If not used, the master station transmits a permission signal to the slave station using the same permission signal slot as the number corresponding to the data signal slot (steps S112, S114, S116, S120). afterwards,
The slave station transmits data to the master station using a data signal slot corresponding to the same number as the permission signal slot received from the master station. For example, the master station has a data signal slot D
If S1 is not used, the permission signal is transmitted to the slave station using the permission signal slot G1, and the received slave station transmits data to the master station using the data signal slot DS1.

In the processing on the master station side, the request signal slots R1 to R12 received from the slave stations are all sequentially processed with the same weight. Similarly, the request signal slots R1 to R12 transmitted to the master station on the slave station side are all sequentially processed with the same weight. However, a certain slave station has a process of randomly selecting the request signal slots R1 to R12 so that transmission requests from a certain slave station and another slave station do not overlap.

In the above-described processing in FIG. 3, the master station sequentially transmits a broadcast signal slot B to each slave station. The slave station can confirm the survival of the master station by the notification signal from the master station. On the other hand, if the slave station is out of order, data transmission from the slave station to the master station is not performed. Further, even if the slave station does not have data to be sent to the master station, no data is sent. Therefore, the master station cannot distinguish whether the slave station cannot transmit data to the master station due to a trouble such as a failure or the slave station simply does not have transmission data. That is, the master station cannot confirm the survival of the slave station unless the slave station actively transmits data.

[0017]

As described above, the slave station does not transmit a response signal to the master station unless transmission data is generated from the slave station to the master station. In this case, the master station cannot receive any signal from the slave station. On the other hand, even when the slave station is stopped due to a failure or the like, the slave station cannot transmit data to the master station. Therefore, there is a problem that the master station cannot distinguish whether transmission data from the slave station to the master station has not been generated or whether the slave station cannot communicate with the master station due to a failure or the like.

Therefore, an object of the present invention is to provide a data communication system capable of solving the above-mentioned problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous embodiments of the present invention.

[0019]

According to one aspect of the present invention, there is provided a data communication system in which a master station and a plurality of slave stations communicate with each other to achieve the above object. In this data communication system, notification timings at which the plurality of slave stations notify the master station are pre-assigned to different timings for the plurality of slave stations, and the master station is assigned to the plurality of slave stations. Means for simultaneously broadcasting a broadcast signal for establishing communication frame synchronization, and the slave station, upon receiving the broadcast signal, each of the slave stations to the master station at the previously assigned notification timing, Response means for responding to the request.

In the response step, when each of the slave stations needs to establish communication with the master station, the slave station establishes communication with the master station using the pre-assigned notification timing. And a non-request means for transmitting a signal other than the request signal to the master station when it is not necessary to establish communication with the master station. .

In the data communication system, the broadcast signal is broadcast to a plurality of slave stations periodically, and an allocating means for assigning a different identification number to the broadcast signal for each cycle, Each may further include means for determining the notification timing based on the specific identification number and an offset time from the notification signal identified by the identification number.

The allocating means may cyclically allocate the identification signal to a plurality of the notification signals.

The non-requesting means may transmit, to the master station, information indicating that the slave station does not have a fault when the slave station does not have a fault.

Note that the above summary of the present invention does not enumerate all of the necessary features of the present invention, and a sub-combination of these features can also be an invention.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention and have the features described in the embodiments. Not all combinations are essential to the solution of the invention. This embodiment is applied to the data communication system shown in FIG.

FIG. 4 shows an example of a communication frame used in the data communication system of the present embodiment. The communication frame has a broadcast signal slot, a reception confirmation signal slot, a request signal slot, a permission signal slot, and a data signal slot. Data communication is performed in units of communication frames.
This is performed by transmitting and receiving one or more communication frames. In addition, the master station and the slave station can know the position of each signal slot by measuring the offset time from the broadcast signal. Hereinafter, how each signal in the communication frame is used will be described.

The broadcast signal is transmitted from the master station to the slave station using broadcast signal slot B. The broadcast signal slot B is
It has a guard time 10, a burst header 12, and a Bch 14. The broadcast signal is sequentially transmitted from the master station to the slave station, and is used as a trigger for establishing frame synchronization of the slave station and for granting permission to start communication.

The reception acknowledgment signal is a reception acknowledgment signal slot A
It is transmitted from the master station to the slave station or from the slave station to the master station using 1 to A4. The reception confirmation signal slot A1 has a guard time 10, a burst header 12, and Ach16. Similarly, the acknowledgment signal slots A2, A3, and A4 also have a guard time and a burst header.

When data is generated from the master station to the slave station, the slave station receiving the data transmits a reception confirmation signal to the master station. When data is generated from the slave station to the master station, the master station receiving the data transmits a reception confirmation signal to the slave station. Therefore, the data transmission source (master station or slave station) receives the acknowledgment signal from the transmission destination (master station or slave station), so that the transmission data reaches the transmission destination (master station or slave station). Can be confirmed.

The request signal is transmitted from the slave station to the master station using 12 request signal slots. The request signal slot has a guard time, a burst header, and Rch.
As a feature of the present embodiment, the request signal slots are divided into priority signal slots (PR1 to PR4) and random request signal slots (RR5 to RR12). The priority signal slot is individually assigned to each slave station. The random request signal slot is basically the same as the prior art described with reference to FIG. The random request signal slot will be dictated.

The permission signal includes permission signal slots G1 to G4.
Is transmitted from the master station to the slave station using. The permission signal slot G1 includes a guard time 10, a burst header 12, a G
ch20. The permission signal slots G2 to G4 also have a guard time and a burst header. The permission signal is transmitted from the master station to the slave station. The master station transmits a permission signal to the slave station as a master station permission response to the request signal slots R1 to R12 from the slave station. Also, when data to be transmitted from the master station to the slave station occurs, a permission signal is transmitted from the master station to the slave station.

The data signal is transmitted from the master station to the slave station or from the slave station to the master station using the data signal slot. The data signal slot (short) DS1 has a guard time 10, a burst header 12, and a DSch 22. Similarly, the data signal slots DS2 and DS3 have a guard time and a burst header. The data signal slot (long) D
L4 is guard time 10, burst header 12, DL
ch (12240) 24. For example, when the slave station transmits data to the master station, the slave station transmits a request signal to the master station. The master station transmits a permission signal to the slave station in response to a request signal from the slave station. The slave stations that are allowed to send data
The data is transmitted to the master station using the data signal slot.
Here, when the data to be transmitted is short, the data signal slots DS1 to DS3 are used, and when the data to be transmitted is long, the data signal slot DL4 is used. The same applies to the case where the master station transmits data to the slave station. The above is the role of each signal slot.

Next, the correspondence between the numbers in each signal slot will be described. Acknowledgment signal slots A1 to A4, permission signal slots G1 to G4, data signal slot DS1
The numbers DS3 and DL4 correspond to each other. For example, when transmitting data from the slave station to the master station, the master station transmits a permission signal to the slave station. At this time, if the master station uses the permission signal slot G1 (20), the slave station receiving the permission signal transmits data to the master station using the data signal slot DS1 (22). The master station that has received the data transmits a reception confirmation signal to the slave station using the reception confirmation signal slot A1 (16). Since the reception confirmation signal, the permission signal, and the data signal include a plurality of slots (the reception confirmation signal slot is A1 to A4, the permission signal slot is G1 to G4, and the data signal slots are DS1 to DS3 and DL4), And a plurality of slave stations can perform data communication.

Next, a description will be given of a request signal slot characteristic of this embodiment. Conventional request signals are all processed with the same weight, as shown in FIGS. That is, the conventional request signal slots R1 to R12 all have the same function. On the other hand, in the present embodiment, as shown in FIG. 4, the request signal slot is divided into two, one of which is a random request signal slot and the other is a priority request signal slot. The random request signal slots are RR5 to RR12, and the priority request signal slots are PR1 to PR4.
Then, the master station can use the priority request signal slot to confirm the existence of the slave station. The random request signal slot is used in the same manner as the conventional request signal shown in FIGS.

FIG. 5 is a diagram showing the setting of the request signal slot of this embodiment for a plurality of continuous frames. FIG. 5A shows a flow of a communication frame used in the information communication system according to the present embodiment, in which a frame # 1, a frame # 2, a frame # 3... assign. Each communication frame has a request signal slot. In FIG. 5B, the request signal slot included in each communication frame is divided into two,
One is a random request signal slot and the other is a priority request signal slot. In FIG. 5B, random request signal slots are RR5 to RR12, and priority request signal slots are PR1 to PR4.

The random request signal slots RR7 to RR1
2 is processed in the same manner as the request signal slot in FIGS. That is, when data to be transmitted from the slave station to the master station occurs, the slave station transmits a request signal to the master station using a random request signal slot. The slave station randomly selects random request signal slots (RR5 to RR12) so as not to overlap with random request signal slots from other slave stations under the same master station, and transmits data to the master station. Make a request.

On the other hand, priority request signal slots PR1 to PR
4 has a function that allows the master station to check the survival status of all slave stations under its control. To fulfill this function, a priority request signal slot is individually assigned to each slave station. The correspondence between each slave station and the priority request signal slot will be described below.

Each communication frame has its own frame number (# 1 to # 9 in FIG. 5). First, slave station numbers 1, 2, 3, and 4 are sequentially allocated to the priority request signal slots PR1 to PR4 of the communication frame number # 1. Therefore, the notification timing to respond to the master station in the order of slave station 1, slave station 2, slave station 3, and slave station 4 is determined by the offset time from the broadcast signal received from the master station. Subsequently, slave station numbers 5, 6, 7, and 8 are sequentially assigned to the priority request signal slots PR1 to PR4 of the communication frame # 2. The same applies to other communication frames # 3 and thereafter. Therefore, each slave station number is sequentially associated with each priority request signal slot PR1 to PR4 of each communication frame by the identification number of the slave station. Associating the identification number with the priority request signal slot is to determine at which notification timing each slave station responds to the master station with a signal such as its own survival status.

Here, each slave station sends a signal as a response to a notification signal from the master station when the priority request signal slot in its own order comes around. This signal is sent regardless of whether the slave station has data to send to the master station. When there is data to be transmitted, a "request signal" is transmitted, and when there is no data to be transmitted, a "signal for survival confirmation" is transmitted. This survival confirmation signal indicates that the slave station has no fault.

When transmitting a request signal, the slave station functions as a means for requesting the master station to establish communication. On the other hand, when transmitting the survival confirmation signal, the slave station functions as a non-requesting unit that transmits a signal other than the request signal. The survival confirmation signal is one form of a signal transmitted by the non-requesting means.

Next, taking as an example a case where the number of priority request signal slots is 4, the number of slave stations connected to the master station is 62, and the own slave station number is 33, the priority station used by the slave station of slave station number 33 is used. 6 shows an example of calculating a request signal slot. First, the slave station establishes synchronization with the master station by the broadcast signal slot B from the master station.
When the authentication of the master station is obtained, the slave station number is assigned from the master station to the slave station. On the other hand, the number of slave stations is sequentially transmitted from the master station by the broadcast signal slot B. From these information, the following calculation is performed.

The quotient obtained by adding the number of slave stations connected to the master station to a value divisible by the number of priority request signal slots and dividing by the number of priority request signal slots is a frame interval. Therefore,

When (62 + 2) ÷ 4 = 16, the frame interval becomes 16, and a communication frame assigned with a period of 16 frames appears. Therefore, the slave station number is cyclically assigned to the priority request signal slot as the identification number of each slave station. Next, a frame number is obtained by adding 1 to a quotient obtained by dividing the own station number by the number of priority request signal slots, and the remainder is a priority slot number.

33 ÷ 4 = 8 remainder 18 + 1 = 9 Therefore, the slave station having the own slave number 33 has the communication frame number #
Nine priority request signal slots R1 are used. Also, 16
The priority request signal slot PR1 is used in the frame cycle. In actual data communication, the position of the slot can be known from the offset time from the broadcast signal of the master station.

If the frame counts of the master station and the slave station do not match, the master station and the slave station cannot recognize the frame period. Therefore, the master station and the slave station synchronize the frame count value according to the frame sequence number in the broadcast signal slot B from the master station.

Here, the master station has a counter that counts up cyclically every frame time within a period longer than the frame period. The frame sequence number is counted up using a counter. The counted-up frame sequence number is notified from the master station to the slave station by the broadcast signal slot B. Therefore,
The slave station obtains information of the current frame number from the received frame sequence number of the broadcast signal slot B. In FIG. 5, the priority request signal slots are PR1 to PR1.
PR4, but the number of priority request signal slots is
It is not limited to four. The priority request signal slot is
It may be allocated discontinuously in the request signal slot.
Next, a flow until the slave station transmits its survival to the master station using the priority request signal slot will be described.

FIG. 6 shows that the slave station selects a priority request signal slot to be used by itself based on a broadcast signal from the master station,
It is a figure which shows the flow which transmits own survival confirmation to a master station.

The slave station receives a notification signal from the master station (step S100). The slave station reads out the number of slave stations connected to the master station from the received notification signal. In addition, the slave station
The frame sequence number is read from the received notification signal, and it is determined whether or not the communication frame should be used by itself (step S103). If the slave station does not respond to the frame, the slave station proceeds to step S106. If there is data to be transmitted to the master station in step S106, a request signal is set in a random request signal slot (step S106).
108), and transmits a signal to the master station (step S11).
6). If there is no data to be transmitted to the master station (step S
106), the process ends.

On the other hand, if the slave station is to respond to the frame (step S103), the slave station determines whether or not the frame is a priority request signal slot (step S104). Step S1
If it is not a priority request slot in step 04, step S106
Proceed to. If there is data to be transmitted to the master station in step S106, a request signal is set in a random request signal slot (step S108), and a signal is transmitted to the master station (step S116). If there is no data to be transmitted to the master station (step S106), the process ends.

If it is a priority request signal slot in step S104, the process proceeds to step S110. Step S1
If there is data to be transmitted to the master station at step 10, a request signal is set in the priority request signal slot (step S11).
2) A signal is transmitted to the master station (step S116). If there is no data to be transmitted to the master station (step S11
0), a survival confirmation signal is set in the priority request signal slot (step S114), and a signal is transmitted to the master station (step S116). That is, even when there is no data to be transmitted to the master station, the slave station uses the assigned priority request signal slot to transmit a survival confirmation signal indicating that no failure has occurred to the master station. Since the priority request signal slot assigned to each slave station rotates at a fixed cycle, each slave station transmits its own survival confirmation signal to the master station at a fixed cycle.

As described above, the slave station always sends a signal to the master station using the assigned priority request signal slot. On the other hand, when the slave station has data to be transmitted to the master station, the slave station can transmit a request signal to the master station using the random request signal slot even at a timing when the priority request signal slot is not turning. it can. The random request signal slot used by the slave station is not limited to a communication frame having a priority request slot of the slave station. Next, a description will be given of a flow in which the master station processes the signal from the slave station processed in the flow of FIG.

FIG. 7 is a diagram showing a flow in which the master station processes a priority request signal slot and a random request signal slot from the slave station.

The master station receives and processes the priority request signal slot and the request signal slot from the slave station (step S10).
0). The processing differs depending on whether or not the priority request signal slot is used (step S102). If Rn is not a priority request signal slot but a random request signal slot, and Rn has a transmission request (step S110), processing is performed in the same manner as the request signal slot in FIG. 3 as follows.

According to the length of the transmission data (step S1)
12) Select the data signal slot DS1 to DS3 or DL4. If the transmission data is short, the use status of the data signal slots DS1 to DS3 is checked in order (steps S114, S116, S118). If the data signal slot DS1 is in use, the data signal slot DS2 is used, and if the data signal slot DS2 is in use, the data signal slot DS3 is used. If the data signal slot DS1 is not used (step S11)
4), the master station transmits a permission signal to the slave station using the permission signal slot G1 (step S124). Similarly, DS
If No. 2 is not used (step S116), a permission signal is transmitted to the slave station using the permission signal slot G2 (step S126). If DS3 is not being used (step S118), a permission signal is transmitted to the slave station using the permission signal slot G3 (step S128). On the other hand, if the transmission data is long (step S112), the usage status of the data signal slot DL4 is checked (step S120). If it is not in use, a permission signal is transmitted to the slave station using the permission signal slot G4 (step S4).
122).

On the other hand, if Rn is a priority request signal slot (step S102) and is not a signal for confirming existence (step S108), there is a transmission request in Rn, so that it is the same as a normal request signal slot. Step S1
12 or less. Also,

Some signal exists in Rn (step S
108), if the signal is a signal for confirming existence (step S108), the process ends. With this survival confirmation signal, the master station can know that there is no failure in the slave station.

By the way, if Rn is the priority request signal slot (step S102) and there is no signal in Rn (step S108), it is understood that some trouble has occurred in the slave station. This is because the slave station does not transmit any data to the master station according to the priority request signal slot to be used by the slave station. Then, a trap notification is sent to the master station management terminal as a failure countermeasure (step S10).
6). Therefore, it can be seen from the trap notification that some trouble has occurred in the slave station.

Therefore, whether or not a failure has occurred in the slave station can be immediately detected from the master station or a terminal on the backbone network to which the master station is connected.
Each slave station has its own signal slot prepared at a constant cycle. Then, the slave station can notify the master station of its own survival using the signal slot allocated to itself. Conventionally, the above advantage can be obtained by using a request signal slot that has been randomly used when communication establishment is necessary for confirming the existence of a slave station. In addition, all the slave stations under the master station are equally confirmed to be alive by the master station, and can uniformly receive service for troubles such as failures, and can receive a simple bandwidth guarantee.

Although the present invention has been described with reference to the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. Various changes or improvements can be added to the above embodiment. It should be noted that such modified or improved embodiments may be included in the technical scope of the present invention.
It is clear from the description of the claims.

[0060]

As is apparent from the above description, according to the present invention, when a master station communicates with a plurality of slave stations, the master station can appropriately confirm the survival of the slave stations under its control. .

[Brief description of the drawings]

FIG. 1 is a conceptual diagram in which a master station and a plurality of slave stations perform communication.

FIG. 2 is a diagram of a communication frame used in a data communication system.

FIG. 3 is a diagram showing a flow of processing of a request signal slot on a master station side.

FIG. 4 is a conceptual diagram of a communication frame according to the embodiment of the present invention.

FIG. 5 is a conceptual diagram illustrating a setting example of a priority request signal slot according to the embodiment of the present invention.

FIG. 6 is a diagram showing a flow of processing on a slave station side for a priority request signal slot according to the embodiment of the present invention.

FIG. 7 is a diagram showing a flow of processing on a master station side of a priority request signal slot and a random request signal slot according to the embodiment of the present invention.

[Explanation of symbols]

 10 guard time 12 burst header 30 master station 32 slave station 34 response 36 broadcast signal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B089 GA21 JA35 JB14 JB23 KA12 KB11 KC29 KE07 MC02 5K032 AA05 BA01 BA02 BA04 CA01 CC03 CC06 CC13 DA01 DA04 EA03 EA05

Claims (5)

[Claims] 1. A data communication system in which a master station and a plurality of slave stations communicate with each other, wherein notification timings at which the plurality of slave stations notify the master station are different for each of the plurality of slave stations. A notification unit that is allocated in advance, and that simultaneously notifies the plurality of slave stations of a notification signal for establishing communication frame synchronization with the plurality of slave stations; and each of the slave stations receives the notification signal. And a response means for responding to the master station at the pre-assigned notification timing. 2. The responding means, when each of the slave stations needs to establish communication with the master station, communicates with the master station using the notification timing assigned in advance. Means for sending a signal requesting the establishment of the master station, and non-request means for sending a signal other than the request signal to the master station when communication with the master station does not need to be established. The data communication system according to claim 1, wherein: 3. The broadcast signal is broadcast to a plurality of slave stations periodically, and an allocating means for allocating a different identification number to the broadcast signal for each cycle, wherein each of the plurality of slave stations is 2. The data communication system according to claim 1, further comprising: means for determining the notification timing based on the specific identification number and an offset time from the notification signal identified by the identification number. 4. The data communication system according to claim 1, wherein said allocating means cyclically allocates the identification signal to the plurality of broadcast signals. 5. The apparatus according to claim 1, wherein the non-requesting means transmits, to the master station, information indicating that the slave station does not have a fault when the slave station does not have a fault. Data communication system.