The classification and principle of the PLC communication -

serial communication: through a pair of wires, will be sent to the receiver to connect, every bits of data transmission, in a specified order, on the same connection wire, in order to send and receive. As shown in the figure below:

PLC communication is usually use serial communication. Standard serial interface for communication line connecting input/output lines as an interface. Connect the appellation of parallel communication lines parallel interface; Connect the appellation serial interface of serial communication line. In a PLC system, commonly used standard serial interface mainly have RS232 interface, RS422 interface, RS485 interface, etc. RS232/422/485 for the PLC system are the most commonly used communication interface, RS232 interface is a kind of computer, PLC control system is the most common standard serial interface, the interface generally use 9 core or 25 core connector, use of the signal name, code, the meaning of the pin shown in the table below:

RS422 interface is a kind of computer, PLC control system in common standard serial interface, known as the 'balance voltage digital interface. Interface connector generally use 9 core, the use of the signal name, code, the meaning of the pin shown in the table below:

RS - Is the RS - 485 interface 422 based on a standard serial interface, also adopted the way of 'balanced differential drive'. The interface RS - All the technical specifications, 422 can be used in RS - 422 communication interface generally use 9 core connector or terminal connections, use of the signal name, code, pin and RS - meaning 422 is the same. N: N network function: is between up to 8 FX series PLC, through the RS - 485 communication connection, soft components are connected, the function of information interchange. One of them as the host, the rest is from the machine ( The master station and from the station) 。 The auxiliary relay on each PLC controller and there is a system in the data register of data sharing, each PLC are specified in this network distribution of their own a piece of data area. For some a PLC, a data area assigned to it will be automatically sent to the other station in the same area, likewise, assigned to other PLC data area, will be automatically transferred to the PLC controller. About the special auxiliary relay description

about the special register data indicate that the network Settings: N: N network Settings only if the program is running or PLC is valid when it is started. ( 1) Set up the workstation number ( D8176） D8176 value in the range of 0 7, the host should be set to 0, is set to 1 - from the station 7 ( 2) Set up from the station number ( D8177） This setting only applies to the master station, D8177 set in the range of 1 - The value of the 7 between the default value is 7 ( 3) Set the refresh range ( D8178） Refresh the scope refers to the master station and from the station Shared auxiliary relay and the scope of the data register. Refresh range consists of the main D8178 to set, can be set to 0, 1, 2, value, corresponding to refresh the scope in the following table:

Shared auxiliary relay and data register table:

is suitable for the FX series PLC network link communication equipment is not all of the FX series PLC controller has the function of parallel link. FX0S,FX1，FX2( C) Series PLC network link function cannot be

4, network link communication wiring N: N network of connection mode 1

N: N network programming example 3 FX2N series PLC through N: N network data exchange. The main X0 - The X3 Y10 - to control from station 1 Y132. No. 1 X0 - from the stand To control 2 X3 Y14 - from the station Y173. No. 2 X0 - from the stand Y20 - X3 to controlling center Parallel link function: 2 is connected to the same series of FX series PLC, the links to software, the function of information interchange. Parallel link special auxiliary relay and special data register table:

parallel link data sharing area table:

2, is suitable for the FX series PLC for parallel link communications equipment FX0S, FX1 series PLC cannot be parallel links, in addition, parallel link also need special communications equipment, such as: 232/422/485 communication boards, adapter, such as the following table lists the parallel link by the combined use of PLC and communication equipment. 2 for wiring occasions

5, parallel link, for example: required: 2 FX2N series PLC for parallel link X0 - master station X7 control Y0 - from the station 日元; X0 - from the station X7 Y0 - controlling center 日元; PLC reliable communication protocol to send and receive data, communication both sides must have a specified data format, synchronously, transmission rate, error correction methods, control characters, etc. , which need special communication protocol. 1 special protocol communications dedicated communication is to point to by special PLC communication tool software installed on the external devices, for the communication of data exchange between PLC and external devices. 2 no protocol communications protocol communication is only need to format data, transmission rate, start/stop code for simple setting, such as between PLC and the external devices for direct data sending and receiving way of communication. 3 bidirectional protocol communication two-way communication is through the communication interface, using PLC communication module information format with external equipment to send and receive data communication mode.

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