The communication instructions of PLC are used to realize data exchange between PLC and other devices or systems.
The following are some common PLC communication instructions:
1. Data transfer instructions:
(1) RS command:
This is the control instruction for data transmission between PLC and peripheral devices.
It specifies the source address (the starting location of the sent data) and the destination address (the storage location of the received data), as well as the amount of data sent and received.
(2) MOV instruction:
Used to transfer data from source address to destination address.
2. Serial communication instructions:
(1) Send instructions (such as SEND, TX, etc.):
Used to send data from PLC to other devices.
(2) Receive instructions (such as RCV, RX, etc.):
Used to receive data from other devices to the PLC.
3. Network communication instructions:
(1) Network read and write instructions:
For example, for some PLCs that support Ethernet communication, there may be special instructions for reading or writing data from other devices on the network.
(2) Email instructions:
In some PLC systems, a mailbox structure is used to send and receive data.
4. Special communication protocol instructions:
(1) Modbus command:
If the PLC supports the Modbus communication protocol, there may be special instructions for implementing Modbus communication.
(2) Profibus instructions:
Similarly, if the PLC supports the Profibus protocol, there may be corresponding instructions.
5. Connect and disconnect instructions:
(1) CONNECT instruction:
Used to establish connections with other devices or systems.
(2) DISCONNECT instruction:
Used to disconnect an established connection.
6. Configuration instructions:
(1) Instructions for setting communication parameters (such as baud rate, data bits, stop bits, etc.).
(2) Instructions to initialize the communication port.
7. Status query instructions:
(1) Instruction to query communication port status.
(2) Instructions to query connection status.
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