JP3443683B2 - Serial communication control system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial communication control system capable of performing serial communication between a central control device and each terminal via a relay device provided between the central control device and a plurality of terminals.

[0002]

2. Description of the Related Art Conventionally, when one central control unit and a plurality of terminals are serially communicated, a polling / selecting method is usually used. That is, in order for the central control unit to obtain the information message from the terminal, the terminal has an individual address, and the central control unit inquires of a predetermined terminal whether or not there is an information message to be transmitted. The corresponding terminal returns data if there is an information message, and transmits no data (EOT) if there is no information message. An error detection code (BCC) for checking an error is added to the data transmitted from the terminal, and the central control unit calculates the BCC of the received data and matches the value of the BCC added to the data. A positive response (AC
If K) does not match and is incorrect, a negative response (NAK) is returned to the terminal, and the communication is completed. After the communication is completed, an inquiry is similarly made to the next terminal. This is the polling method.

When the central controller transfers an information message to a terminal, it adds BCC to the message and sends it to the terminal to which the message is to be sent. After receiving the message, the corresponding terminal calculates BCC, and returns ACK if normal and NAK if incorrect, and the communication is completed. This is the selecting method.

[0004]

In the conventional serial communication control system, the number of terminals connected to one central control unit is limited, and the distance between communications is also limited. If the number of terminals is greater than the maximum number of connections, or if the network distance is longer than the communicable distance, some means needs to be provided.

One method is to add another central control device and connect the central control devices with an information system LAN or the like. However, with such a configuration, an expensive central control device is added, resulting in high cost, and it is necessary to newly create a program for communicating between the central control devices.

[0006] Another method is to extend a relay device provided between the central control device and the terminal. With this method, an inexpensive control system LAN can be used for the network between the central control device and the relay device, and at the same time, a versatile and low-cost relay device can be used. However, when the relay device is provided in this way, there arises a problem of whether the BCC added to the message transmitted from the terminal is checked by the central control device or the relay device. In other words, the central controller is BC
If C is checked, the response data from the terminal to the polling transmitted from the central control device passes through the relay device, and the responsiveness deteriorates accordingly. Therefore, it is not suitable for a system that requires real time. In addition, if the relay device checks the BCC, the responsiveness is better than that of the above-mentioned central control device checking the BCC, but the range in which the BCC is calculated changes depending on the system. Only applicable to. In addition, the relay device is BC
When the check of C is performed, when the data is sent to the central control unit, the data of the check result may be destroyed.

An object of the present invention is to provide a serial communication control system in which responsiveness, versatility, and reliability are not impaired even when the number of terminals or the distance between networks exceeds a constraint condition.

[0008]

In order to achieve the above object, according to the present invention, one relay device and a plurality of terminals are connected by a network using serial communication, and the relay device has one central control. A serial connection for transmitting and receiving a message by serial transmission between the central control device and the relay device, and between the relay device and the plurality of terminals. In the communication control system, a switching unit that switches checking of an error detection code (BCC) added to a message transmitted from the terminal for detecting an error between a case where the central control device performs and a case where the relay device performs. It is characterized by the provision of.

Further, the present invention has a system configuration in which one relay device and a plurality of terminals are connected by a network using serial communication, and the relay device is connected by one central control device by a control network. I am doing
The central control device creates a message to be transmitted to one of the plurality of terminals in the format for the control network, transmits the message to the relay device, and transmits the message from the relay device. With the function of receiving a message, the relay device receives the message transmitted by the central control device, converts the received message into a format for the serial communication, and transmits the message to the plurality of terminals, In a serial communication control system having a function of receiving a message transmitted by the plurality of terminals, converting the received message into a format for the control system network, and transmitting the message to the central controller, the serial communication control system transmits the message from the terminal. Error detection code (BCC) check that is added to a message to detect an error. And it is characterized in that a switching means for switching to the case where the said relay device and when the central control device performs performed.

According to each of the above configurations, a system that requires responsiveness, a system that does not require responsiveness but requires reliability, or an error detection code (BCC) check for a message from a terminal If the method is unknown, or if the polling / selecting process is completely entrusted to the relay device, the settings of the relay device can be switched, so that a flexible configuration can be provided according to the system.

In constructing the serial communication control system, the following elements can be added. (1) When the central control unit checks the BCC, the central control unit sends back an affirmative response (ACK) to the terminal when normal and a negative response (NAK) when it is incorrect. Constitute. (2) When the relay device checks the BCC, the relay device normally acknowledges (ACK).
Is configured to return a negative response (NAK) to the terminal when an error occurs. (3) The relay device is configured to check the BCC according to a command from the central controller. (4) The relay device, when returning the ACK to the terminal, executes a process of converting a message from the terminal into a format for the control network and transmitting the message to the central controller. When returning the NAK to the terminal, the process is not executed. (5) The relay device is configured to poll the plurality of terminals in advance and, when requested by the central control device, transmit the status data of the plurality of terminals to the central control device. (6) When selecting data for the plurality of terminals is transmitted as one message from the central control device to the relay device, the relay device is configured to select the corresponding terminal. (7) The relay device is configured to, when an event occurs in any of the plurality of terminals, transmit change data due to the event occurrence to the central control device, without depending on a request command from the central control device. To do. (8) The central control device retransmits the NAK when polling the terminal to the relay device, a timeout time when there is no response at the time of polling, and the NAK when selecting to the terminal. It is configured to set the number of retransmissions and the timeout time when there is no response at the time of selecting. (9) A plurality of relay devices are connected to the central control device via the control network.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a system configuration diagram when performing serial communication according to the present invention. As shown in the figure, the central control device 1 is connected to a plurality of relay devices 2 to 4 via a control system network 5. The relay device 2 is connected to the terminals 6 to 8 and the serial interface 15, the relay device 3 is connected to the terminals 9 to 11 and the serial interface 16, and the relay device 4 is connected to the terminals 12 to 14 and the serial interface 17 of RS-485. ing.

First, the relay devices 2 to 4 are numbered in advance before the system is started up. Numbering is from relay device 2
4 Dip switch settings are installed on each. When the relay devices 2 to 4 are powered on, the relay devices 2 to 4 assign their own numbers to the relay device number 19 in the initial setting format 18 shown in FIG. Data indicating that the initial setting is not set is written and transmitted to the write / initial setting completion flag 20. After receiving the data, the central control device 1 recognizes that the relay devices 2 to 4 have not completed the initialization, and the relay device number 19 in the initialization format 18 is recognized.
Write the number of the relay device on the initial setting / control flag 2
Data indicating the initial setting is written in 1, and the corresponding portion is transmitted to the embedded relay devices 2 to 4 in the same manner.

A communication processing type 22 in the initial setting format 18 indicates a processing method relating to communication of the relay devices 2 to 4. When the data is "1", the relay devices 2 to 4 transmit from the terminals 6 to 14. B added to the message
It is not necessary to check the value of CC, but the central controller 1 checks BCC. The data is "2"
In the case of "4", the relay devices 2 to 4 check the BCC for the message transmitted from the terminals 6 to 14. In addition, since the calculation method of BCC differs depending on the system, the data is divided into several types, “2” to “4”. When the data is "5", the relay devices 2 to 4 independently poll the terminals 6 to 14 without depending on the command of the central controller 1, and when a new event occurs in the terminals 6 to 14, Transmitting to the central control device without permission, and further from the central control device 1 to the relay devices 2 to 4 the terminals 6 to 14
When the control data is transmitted, the relay devices 2 to 4 confirm the contents of the data and arbitrarily control the corresponding terminal among the terminals 6 to 14.

The number of retransmissions / timeout time 23 is set to the maximum number of times of retransmission when the response data to the polling to the terminals 6 to 14 is a negative response, the timeout time when there is no response to the polling, and the terminal 6 ~ 14
Setting of the maximum number of retransmissions of the relay devices 2 to 4 when a negative response is returned from the terminals 6 to 14 at the time of selecting
It shows setting of a timeout time when there is no response from the terminals 6 to 14 during selecting.

When the relay devices 2 to 4 receive the above-mentioned initialization format 18 from the central control device 1, they set a flag indicating that the initialization is completed in the initialization completion flag 20 to complete the initialization.

When the initial setting of the relay devices 2 to 4 is completed,
Communication processing type 22 in format 18 for initial setting
, The central controller 1 starts polling / selecting for the terminals 6-14. The transmission format to the relay devices 2 to 4 at the time of polling is as shown in the upper part of FIG.
Data 2 sent on the serial interface 15 to 17
6, a header and a footer are added so that the header and footer can be sent to the control network 5. In the transmission format 24, the relay device number 19 is the number of the destination relay device, the initialization / control flag 21 is data for control, and the RS-485 data 26 is the terminals 6 to 1.
Polling data to be sent to No. 4 is entered. Polling data 2
An example of No. 7 is shown on the lower side of FIG. Here, the PDA 28 indicates the address of the polling destination terminal, the DLE 29 indicates the extension of the transmission control, and the ENQ 30 indicates the inquiry to the terminal. The text length of the polling data 27 is written in the RS-485 data length 25.

The relay devices 2 to 4 receive the transmission data 24, extract the RS-485 data 26 by the RS-485 data length 25, and transmit it to the terminals 6 to 14.

The terminal sent to itself returns an EOT indicating that there is no data if there is no data, and returns the message shown as an example in FIG. 4 if there is data.
In response to the message, the relay devices 2 to 4 according to the setting contents of the communication processing type 22 of the initial setting data 18 are BC.
Judge whether to check C or not.

Next, the BCC check is performed by the relay devices 2 to 4.
Will be described and the case where the central control device 1 performs. First, when the relay devices 2 to 4 perform the BCC check, the relay devices 2 to 4 perform the BCC calculation, and if they are correct, an affirmative response (ACK) is given, and if they are incorrect, a negative response (NA) is given.
K) is returned to the terminal. Also, if the message is correct, R in the terminal receiving format 24 shown in FIG.
Received message and RS-4 in S-485 data 26
The data length of the received message is written in the 85 data length 25, and is transmitted to the central controller 1. FIG. 5 shows this situation in a transmission sequence.

The central control unit 1 checks the BCC.
Relay device 2-4, RS-485 data 2
The received message is written as it is in 6 and transmitted to the central control unit 1. The central controller 1 performs BCC calculation of the part of the received message transmitted from the terminals 6 to 14,
If it is correct, ACK is sent back, and if it is wrong, NAK is sent back to the relay devices 2 to 4 using the terminal control format 24. The relay devices 2 to 4 use RS-485 data 26 to RS.
-485 Extracts only 25 minutes of data length and transmits to terminals 6-14. FIG. 6 shows this situation in a transmission sequence.

Similar processing is performed when selecting from the central control unit 1 to the terminals 6 to 14. The ACK / NAK check transmitted from the terminals 6 to 14 can be switched by the initial setting by the central control unit 1 or the relay units 2 to 4.

When the data of the communication processing type 22 in the initialization format 18 is "5", the relay devices 2 to 4 are independent of the instruction of the central control device 1 and independently of the terminals 6 to 14. When any new event occurs in the terminals 6 to 14, the change data due to the event occurrence is transmitted to the central controller 1. FIG. 7 shows this situation in a transmission sequence. The format to be transmitted to the central controller 1 is RS-
The format is unrelated to the message format of 485. In the figure, No. 1 and No. 2 are machine numbers.

It is to be noted that the relay devices 2 to 4 not only transmit the change data to the central control device 1 when the states of the terminals 6 to 14 change, but also the terminals 6 to 14 from the central control device 1 to the relay devices 2 to 4. It is also possible to add a function to inquire about the current state of. In this case, according to the request data from the central control device 1, the relay devices 2 to 4 are sent to the central control device 1 by the terminal 6
The state of ~ 14 is notified. FIG. 8 shows this situation in a transmission sequence.

Similarly, in controlling the terminals 6 to 14, the relay devices 2 to 4 confirm the contents of the data transmitted from the central control device 1 and arbitrarily select the corresponding one of the terminals 6 to 14. A control function can be added. That is, the selecting data from the central control unit 1 to the terminals 6 to 14 is treated as one message by the relay unit 2
4 to 4, the relay devices 2 to 4 select the corresponding terminals. Figure 9
Shows this situation in a transmission sequence.

As described above, according to the present invention, by transmitting the initial settings from the central control device 1 to the relay devices 2 to 4, the processing methods of the relay devices 2 to 4 can be divided into three types. The first is the relay devices 2 to 4 and the terminals 6 to 14.
It is a method of performing BCC determination for a message transmitted from the. In this case, ACK /
Since NAK is returned directly by the relay devices 2 to 4, it is not necessary to inquire the central control device 1 about the BCC determination.
As a result, the time is shortened and the responsiveness is improved. Further, since the central control unit 1 does not need to determine the BCC, the load of arithmetic processing of the microprocessor mounted in the central control unit 1 is reduced.

Second, the relay devices 2 to 4 are terminals 6 to 14.
The header for the control network as it is, without judging the BCC for the message sent from
This is a system in which a footer is added and sent to the central control unit 1, and the central control unit determines the BCC. In this case, the relay devices 2 to 4 do not need to know the BCC calculation method, and thus can be used for general purposes. Further, the central control unit 1 checks the BCC, and the terminals 6 to 14 receive the AC
Since the reply of K / NAK is performed, the message is surely delivered to the central control unit 1 and the reliability is improved.

The third problem is that the relay devices 2 to 4 are used for general purposes, but the relay devices 2 to 4 poll the terminals 6 to 14 regardless of the central control unit 1. This is a method of transmitting to the central controller 1 when any new message is received by the terminals 6 to 14. In this case, the central control unit 1 does not need to poll the terminals 6 to 14, so that the load of the arithmetic processing of the microprocessor mounted in the central control unit 1 is reduced and the control system network 5 is connected. The amount of flowing data is also reduced. Further, since the data sent to the control system network 5 may be in a format unrelated to the RS-485 message format, it can be processed into a format that the central control unit 1 can easily process.

In the above embodiment, one relay unit is connected to one central control unit, and three relay units are connected to each terminal, but in reality, the central control unit is connected. Up to 63 relay devices can be connected to one device, and up to 31 terminals can be connected to each relay device. The maximum length of control system network is 2 km and RS.
-485 can be transmitted over a maximum distance of 1.2 km.

[0030]

As described above, according to the present invention,
By providing an inexpensive and versatile relay device for serial communication, the number of terminals that can be connected to each central control device can be increased, and the transmission distance of the system can be increased, resulting in a low-cost system configuration. It is possible to build up.

In addition, if a system that requires responsiveness, a system that does not require responsiveness but requires reliability, or a method of checking BCC for a message from a terminal is unknown, a complete polling / selecting process is performed. Since it is possible to switch the setting of the relay device depending on the case of leaving the relay device to the relay device, it is possible to provide a flexible configuration according to the system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a serial communication control system according to the present invention.

FIG. 2 is a diagram showing a transmission format for initial setting on a control system network between a central control device and a relay device.

FIG. 3 is a diagram showing a transmission format for control of a terminal to be sent to a control system network or for message data from the terminal.

FIG. 4 is a diagram showing a message format on RS-485.

FIG. 5 is a diagram showing a transmission sequence when an error detection code (BCC) is checked by a relay device.

FIG. 6 is a diagram showing a transmission sequence when an error detection code (BCC) is checked by a central controller.

FIG. 7 is a diagram showing a transmission sequence when transmitting to the central control device only when the state of the terminal changes.

FIG. 8 is a diagram showing a transmission sequence when a status of a terminal is transmitted in response to a request from a central control device.

FIG. 9 is a diagram showing a transmission sequence when the relay device selects a plurality of terminals.

[Explanation of symbols]

1 Central Control Unit 2 to 4 Relay Device 5 Control System Network 6 to 14 Terminals 15 to 17 RS-485 Network 18 Relay Device Initial Setting Transmission Format 19 Code indicating the machine number of the relay device 20 Initialization of the relay device is completed Code 21 indicating whether or not it is set Code 22 for discriminating between initial setting data and control data 22 Code indicating the processing method of the relay device Code 24 for setting the number of retransmissions and timeout time 24 Terminal control / reception transmission format 25 RS-485 26 indicating the data length of RS-485 area 27 storing the data of RS-485 28 code indicating the address of the terminal of the polling destination 29 code indicating the extension of the transmission control 30 code indicating the inquiry to the terminal

Claims (11)

(57) [Claims] 1. A relay device and a plurality of terminals are connected by a network using serial communication, and the relay device has a system configuration in which it is connected by a central control device and a control network. In a serial communication control system that transmits and receives messages by serial transmission between the central control device and the relay device and between the relay device and the plurality of terminals, an error added to a message transmitted from the terminal An error detection code (BCC) check for detecting the error is provided with a switching means for switching between a case where the central control device performs the check and a case where the relay device performs the check. 2. A relay device and a plurality of terminals are connected by a network using serial communication, and the relay device has a system configuration in which one relay device and a control system network are connected, The central control device creates a message to be transmitted to one of the plurality of terminals in the format for the control network, transmits the message to the relay device, and transmits the message from the relay device. A function of receiving a message, the relay device receives the message transmitted by the central control device, converts the received message into a format for the serial communication, and transmits the message to the plurality of terminals, The message transmitted by the plurality of terminals is received, and the received message is sent to the control network. In a serial communication control system having a function of converting the format into a format and transmitting to the central control unit, an error detection code (BCC) for detecting an error added to a message transmitted from the terminal is checked by the central control unit. A serial communication control system comprising switching means for switching between a case where a control device performs and a case where the relay device performs. 3. The serial communication control system according to claim 1, wherein, when the central control unit checks the BCC, the central control unit receives an acknowledgment (AC) when normal.
K), and a negative response (NAK) is returned to the terminal in case of error, a serial communication control system. 4. The serial communication control system according to claim 1, wherein when the relay device checks the BCC, the relay device gives an acknowledgment (ACK) when normal and an error message. In this case, a negative communication (NAK) is returned to the terminal, and the serial communication control system is characterized. 5. The serial communication control system according to claim 4, wherein the relay device checks the BCC according to a command from the central control device. 6. The serial communication control system according to claim 4, wherein the relay device converts a message from the terminal into a format for the control system network when returning the ACK to the terminal. Then, the processing for transmitting to the central control unit is executed, and the NAK is sent to the terminal.
The serial communication control system is characterized in that the above-mentioned processing is not executed when sending back. 7. The serial communication control system according to claim 1, wherein the relay device polls the plurality of terminals in advance, and when the central control device requests the relay device, the plurality of the plurality of terminals are polled. A serial communication control system, characterized in that status data of a terminal is transmitted to the central control unit. 8. The serial communication control system according to claim 1, wherein when the central control device sends selecting data for the plurality of terminals to the relay device as one message, the relay device Is a serial communication control system characterized by performing selection for a corresponding terminal. 9. The serial communication control system according to claim 1, wherein the relay device does not depend on a request command from the central control device when an event occurs in any of the plurality of terminals, A serial communication control system, wherein the change data due to the occurrence of the event is transmitted to the central control device. 10. The serial communication control system according to claim 1, wherein the central control unit transmits to the relay unit the number of times NAK is retransmitted when polling the terminal and a response when polling. A serial communication control system, comprising: setting a timeout time when there is no transmission, a number of times NAK is retransmitted at the time of selecting to the terminal, and a timeout time when there is no response at the time of selecting. 11. The serial communication control system according to claim 1, wherein a plurality of the relay devices are connected to the central control device via the control network. Control system.