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PHP and Modbus TCP: Understanding the Modbus protocol and its related parameters
Abstract:
In industrial control systems, Modbus is a commonly used communication protocol for data interaction between devices . This article will introduce the basic principles and related parameters of the Modbus TCP protocol, and provide PHP code examples to help readers understand and apply the Modbus TCP protocol.
1. Introduction to Modbus TCP protocol
Modbus TCP is a variant of the Modbus protocol based on the TCP/IP protocol, which allows multiple devices to communicate through Ethernet. Modbus TCP uses a simple command/response model, and devices exchange data by reading and writing registers.
The basic principles of the Modbus TCP protocol are as follows:
2. Modbus TCP parameters
When using the Modbus TCP protocol, you need to understand the following important parameters:
3. PHP code example
Use the PHP library Phpmodbus (https://github.com/r-vnc/phpmodbus) to easily communicate with Modbus TCP devices. Below is a simple example that demonstrates how to read data from a holding register using the Phpmodbus library.
195e1d4bb30abcf3adb8bbc81725a8bdreadMultipleRegisters(1, $address, $quantity);
// Output the read data
if(!$data){
echo "读取错误!";
}else{
echo "读取到的数据:
";
foreach($data as $value){ echo $value . "
";
}
}
?>
In the above example, we created a ModbusMaster object and specified the IP address and port number of the Modbus server. Then, we use the readMultipleRegisters function to read the data in the holding register and print the result.
This is just a simple example. In actual use, more complex operations may be required based on specific needs, such as writing data or using other function codes.
Conclusion:
Modbus TCP is a commonly used industrial control system communication protocol that is simple to use and easy to implement. This article introduces the basic principles and related parameters of the Modbus TCP protocol, and provides an example of using the PHP library Phpmodbus to communicate with a Modbus TCP device. Readers can expand and apply it according to actual needs to achieve more complex Modbus TCP communication functions.
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