Simple protocol conversion is the most common and prevalent Modbus gateway function, and also the most efficient Modbus gateway mode for data processing. It simply extracts key fields from the data and then encodes the extracted data using another protocol (Modbus RTU and Modbus TCP protocols) before sending it.
Demo Request and Data Analysis
To accurately and intuitively demonstrate Modbus data frames, standard Modbus debugging tools are used for testing. Modbus Poll and Modbus Slave are not free software, but they are available for a free 30-day trial. For long-term use, please purchase the full version.
The device uses an NS1-TB serial server and is configured with the parameters shown in the following figure:
Open the Modbus Poll software, click Connection to connect to the serial port server and configure the communication protocol, as shown in the following figure:
Turning off automatic reading facilitates data frame analysis. Configuring the host request first may cause device request timeouts, but this is not a concern. Once the slave simulation is complete, response timeouts will not occur.
Open Modbus Slave, click Connection to connect to the serial server and configure the communication protocol. The master device uses a network connection, while the slave device needs to use a serial connection, as shown in the following figure:
Open the data monitoring serial port. The Poll and Slave methods are the same, as shown in the figure:
Click to read the registers once. The 10 registers cannot be directly displayed in the debug window, so reduce the number of registers to read.
While "simple protocol conversion" offers high processing efficiency, it cannot handle multi-host requests. Therefore, "multi-host mode and storage gateway" are needed. We will discuss the multi-host mode and storage gateway operation modes of serial servers in detail next time.