CN101232425B - A peer-to-peer control method for master-slave stations in a bus-type distributed control system - Google Patents

Abstract

The invention provides a master-slave station-to-end control method of a bus-type distributed control system. Compared with the token control method and the standard data communication control procedure method commonly used at present, the method has the advantages of simple implementation, high efficiency, and small resource occupation. Features, this method is especially suitable for half-duplex bus-type distributed control systems in hardware, such as RS-485 bus, etc. In terms of control methods, simple and efficient peer-to-peer control functions are realized through unique control signs and cooperative control processes.

Description

A peer-to-peer control method for master-slave stations in a bus-type distributed control system

technical field

The invention relates to a master-slave station communication technology of a bus-type distributed control system, in particular to a master-slave station-to-end control method of a bus-type distributed control system.

Background technique

With the increasing complexity of control systems, a large number of control systems have changed from single-machine control to multi-machine centralized control, which is also called distributed control. In the embedded field, a distributed control system coordinates and controls multiple slave processors to complete the control function by a master processor. Usually we call the control module composed of the master processor a "master station", and each slave processor consists of The control module is a "slave". Distributed control requires that the master station and the slave station must be able to communicate with each other. Currently, the master-slave station communication connection methods commonly used include RS-485, RS-422, CAN, Ethernet, etc. Among many methods, the RS-485 method is simple and reliable. , long transmission distance, low cost and other advantages, it is widely used in fields ranging from board-level communication to building-to-building communication.

Since the RS-485 link is a half-duplex communication link, that is, only one station is allowed to send data on the bus link at each moment, otherwise data conflicts will occur and the data will be destroyed. Therefore, in the control system based on RS-485 mode, one station is usually set as the master station, and the other stations are slave stations, and the master station coordinates the communication of each slave station. The traditional method for the master station to coordinate the slave station is to use the token method, and the control characteristics are briefly described as follows:

(1) The control of the master station to the slave station is usually divided into query frame, setting frame and polling frame. When the slave station receives the query frame or setting frame, it passively responds to the content in the frame, and when The slave station can actively send data to the master station to obtain the data it needs from the master station. Usually the master station will send out polling frames at regular intervals and with high density, while query frames and setting frames are usually sent only when needed.

(2) The slave station needs to obtain the permission from the master station to send the token before it can actively initiate the command request from the slave station to the master station. When the master station responds to the command request from the slave station to the master station, it cannot simultaneously query the Real-time data.

(3) After the master station has processed the command request from the slave station to the master station, the master station needs to perform the operation of querying the data of the slave station in addition to obtain the real-time data of the slave station.

Of course, some standard data communication control procedures can also be used for master-slave communication, such as ADCCP, SDLC/HDLC, etc., but whether the token method described above or the standard data communication control procedures are used, the disadvantages are that the implementation is more complicated and costly. More processor resources.

Contents of the invention

The object of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art, and provide a simple and efficient master-slave station-to-end control method of a bus-type distributed control system.

The purpose of the present invention is achieved through the following technical solutions: a master-slave station-to-end control method of a bus type distributed control system, which comprises the following steps:

(1) Each slave station is in the receiving state, the master station sends a command to slave station 1 through the bus, and waits for the receiving slave station to return after sending;

(2) Because each slave station has an independent address, the slave station address will be specified in the command issued by the master station, so all slave stations can receive the master station command, but only the slave station that matches the address in the master station command Station 1 will respond. Slave station 1 recognizes the command and completes processing to form a master station command to return a data packet "A". At the same time, check whether this station has a command request to operate the master station. A" directly returns to the master station; if slave station 1 has an operation command request to the master station, the master station command return data packet "A" will be returned to the master station together with slave station 1's operation command packet "B" to the master station , at this time, the master station command return data packet "A" and the slave station 1 to the master station operation command packet "B" are separated by the reverse command special identifier "F", and then the slave station 1 enters the waiting master station return status;

(3) When the master station receives the data returned from slave station 1, the master station will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice: first process the master The station command returns the data packet "A", and then processes the operation command packet "B" from the slave station 1 to the master station, and obtains the returned data packet "B1". After obtaining "B1", the corresponding command from the master station to the slave station 1 is generated again , the command is returned to slave station 1 together with "B1", and the command and the returned data packet "B1" are separated by the reverse command special identifier "F";

(4) After the slave station 1 receives the command from the master station, it will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice. 1 command to form the master station command return data packet "A", and then process the return data packet "B1" from slave station 1 to the master station operation command packet "B". After the above processing is completed, slave station 1 needs to judge whether there is any For the operation command request of the master station, if there is, the master station command return data packet "A" and the operation command packet "B" of the slave station 1 to the master station are returned to the master station together, and the master station command returns the data packet "A" and the operation command packet "B" of slave station 1 to the master station are separated by the special identifier "F" of the reverse command, and then slave station 1 enters the state of waiting for the master station to return, and returns to step (3);

(5) When the slave station 1 has no operation command request to the master station, the slave station 1 only returns the master station command return data packet "A" directly to the master station, and then the slave station 1 enters the receiving state;

(6) After the master station receives and processes the master station command return data packet "A" returned by slave station 1, it forms a command to the next slave station (such as slave station 2).

In order to better realize the present invention, the bus-type distributed control system is a half-duplex bus-type distributed control system.

The half-duplex bus-type distributed control system is a bus-type distributed control system in RS-485 mode; when the master station sends data, it first sets the RS-485 chip to send the enabling pin "TX_EN"; after the transmission is completed, close the RS- The 485 chip transmits the enable pin "TX_EN" to make it enter the receiving state; when the slave station 1 sends data, it also sets the RS-485 chip transmit enable pin "TX_EN", and then sends data to the bus, and closes the RS after the transmission is completed. The -485 chip transmits the enable pin "TX_EN" to make it enter the receiving state.

The commands include a poll command "L", or a query command "Q", or a set command "C".

Compared with the prior art, the present invention has the following advantages and beneficial effects: the implementation method is simple, the communication efficiency is improved, and the polling cycle is shortened. When the number of slave stations is relatively large, the polling speed is particularly improved. The above is a half-duplex bus-type distributed control system, such as RS-485 bus, etc. In terms of control methods, through unique control signs and cooperative control processes, simple and efficient master-slave system peer control functions are realized.

(1) Each polling command, query command, and setting command of the host can simultaneously obtain the latest real-time data of the slave station and the command request from the slave station to the master station.

(2) The local command and the execution result of the peer command are sent back to the peer together, which is highly efficient, and the two commands are separated by the reverse command identifier.

(3) After receiving the returned data, the master station or the slave station first recognizes whether there is a reverse command identifier, so as to process the command return and command request respectively.

Description of drawings

Fig. 1 is the structural principle diagram of existing bus type distributed control system;

Fig. 2 is the structural schematic diagram of the bus type distributed control system of RS-485 mode;

Fig. 3 is a control flowchart of a master-slave station-to-end control method of a bus-type distributed control system according to the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Embodiment one

Figure 1 is a schematic diagram of the structure of the existing bus-type distributed control system. The master station is connected to each slave station through a bus driver.

As shown in Figure 2, the bus type distributed control system of the present invention is the bus type distributed control system of RS-485 mode, and the MCU (microcontroller) of master station communicates with the MCU of each slave station by RS-485 driver chip Connection, usually the RS-485 driver chip is in the receiving state. When sending data, make it work in the sending state, and immediately make it work in the receiving state after sending the data.

As shown in Figure 3, the steps of the master-slave station-to-end control of a bus-type distributed control system of the present invention are as follows:

(1) Each slave station is in the receiving state, the master station sends a command to slave station 1 through the bus, and waits for the receiving slave station to return after sending;

(2) Because each slave station has an independent address, the slave station address will be specified in the command issued by the master station, so all slave stations can receive the master station command, but only the slave station that matches the address in the master station command Station 1 will respond. Slave station 1 recognizes the command and completes processing to form a master station command to return a data packet "A". At the same time, check whether this station has a command request to operate the master station. A" directly returns to the master station; if slave station 1 has an operation command request to the master station, the master station command return data packet "A" will be returned to the master station together with slave station 1's operation command packet "B" to the master station , at this time, the master station command return data packet "A" and the slave station 1 to the master station operation command packet "B" are separated by the reverse command special identifier "F", and then the slave station 1 enters the waiting master station return status;

(3) When the master station receives the data returned from slave station 1, the master station will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice: first process the master The station command returns the data packet "A", and then processes the operation command packet "B" from the slave station 1 to the master station, and obtains the returned data packet "B1". After obtaining "B1", the corresponding command from the master station to the slave station 1 is generated again , the command is returned to slave station 1 together with "B1", and the command and the returned data packet "B1" are separated by the reverse command special identifier "F";

(4) After the slave station 1 receives the command from the master station, it will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice. 1 command to form the master station command return data packet "A", and then process the return data packet "B1" from slave station 1 to the master station operation command packet "B". After the above processing is completed, slave station 1 needs to judge whether there is any For the operation command request of the master station, if there is, the master station command return data packet "A" and the operation command packet "B" of the slave station 1 to the master station are returned to the master station together, and the master station command returns the data packet "A" and the operation command packet "B" of slave station 1 to the master station are separated by the special identifier "F" of the reverse command, and then slave station 1 enters the state of waiting for the master station to return, and returns to step (3);

(5) When the slave station 1 has no operation command request to the master station, the slave station 1 only returns the master station command return data packet "A" directly to the master station, and then the slave station 1 enters the receiving state;

(6) After the master station receives and processes the master station command return data packet "A" returned by slave station 1, it forms a command to the next slave station (such as slave station 2).

When the master station sends data, first set the RS-485 chip transmission enable pin "TX_EN"; after the transmission is completed, turn off the RS-485 chip transmission enable pin "TX_EN" to enter the receiving state; slave station 1 sends data At the same time, set the RS-485 chip transmission enable pin "TX_EN", and then send data to the bus. After the transmission is completed, turn off the RS-485 chip transmission enable pin "TX_EN", so that it enters the receiving state.

The above control steps can also be applied to the control process when the master station sends a query command "Q" or a setting command "C" to the slave station.

As described above, the present invention can be preferably carried out.

Claims (4)

1. A master-slave station-to-end control method of a bus type distributed control system, is characterized in that comprising the following steps: (1) Each slave station is in the receiving state, the master station sends a command to slave station 1 through the bus, and waits for the receiving slave station to return after sending; (2) Because each slave station has an independent address, the slave station address will be specified in the command issued by the master station, so all slave stations can receive the master station command, but only the slave station that matches the address in the master station command Station 1 will respond. Slave station 1 recognizes the command and completes processing to form a master station command to return a data packet "A". At the same time, check whether this station has a command request to operate the master station. A" directly returns to the master station; if slave station 1 has an operation command request to the master station, the master station command return data packet "A" will be returned to the master station together with slave station 1's operation command packet "B" to the master station , at this time, the master station command return data packet "A" and the slave station 1 to the master station operation command packet "B" are separated by the reverse command special identifier "F", and then the slave station 1 enters the waiting master station return status; (3) When the master station receives the data returned from slave station 1, the master station will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice: first process the master The station command returns the data packet "A", and then processes the operation command packet "B" from the slave station 1 to the master station, and obtains the returned data packet "B1". After obtaining "B1", the corresponding command from the master station to the slave station 1 is generated again , the command is returned to slave station 1 together with "B1", and the command and the returned data packet "B1" are separated by the reverse command special identifier "F"; (4) After the slave station 1 receives the command from the master station, it will first identify whether there is a reverse command special identifier "F" in the returned data, and if there is, it will process the returned data twice. 1 command to form the master station command return data packet "A", and then process the return data packet "B1" from slave station 1 to the master station operation command packet "B". After the above processing is completed, slave station 1 needs to judge whether there is any For the operation command request of the master station, if there is, the master station command return data packet "A" and the operation command packet "B" of the slave station 1 to the master station are returned to the master station together, and the master station command returns the data packet "A" and the operation command packet "B" of slave station 1 to the master station are separated by the special identifier "F" of the reverse command, and then slave station 1 enters the state of waiting for the master station to return, and returns to step (3); (5) When the slave station 1 has no operation command request to the master station, the slave station 1 only returns the master station command return data packet "A" directly to the master station, and then the slave station 1 enters the receiving state; (6) After the master station receives and processes the master station command return data packet "A" returned by slave station 1, it forms a command to the next slave station. 2. A peer-to-peer control method for a master-slave station in a bus-type distributed control system according to claim 1, characterized in that: the bus-type distributed control system is a half-duplex bus-type distributed control system. 3. according to claim 2 said a kind of bus type distributed control system master-slave station opposite control method, it is characterized in that: said half-duplex bus type distributed control system is the bus type distributed control system of RS-485 mode; When the station sends data, first set the RS-485 chip transmission enable pin "TX_EN"; after the transmission is completed, turn off the RS-485 chip transmission enable pin "TX_EN" to enter the receiving state; when the slave station 1 sends data Also set the RS-485 chip transmission enable pin "TX_EN", and then send data to the bus. After the transmission is completed, turn off the RS-485 chip transmission enable pin "TX_EN", so that it enters the receiving state. 4. A master-slave station-to-end control method of a bus-type distributed control system according to claim 1, characterized in that: the command includes polling command "L", or query command "Q", or setting command "C ".

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