The Modbus gateway is to convert a Modbus protocol frame into other protocol frames.
For example, the data of Modbus RTU and Modbus TCP data are converted to each other; the host request and slave response can also be developed for application development to improve the efficiency of protocol conversion; for example, the multi-host gateway that handles multi-host requests improves the efficiency of multi-host request responses The storage gateway replaces the active reporting of the Modbus request initiated by the host.
The device is in Modbus gateway mode to ensure Modbus conversion efficiency and discard non-Modbus data to prevent interference to the serial bus.
Several common Modbus gateways
The Modbus gateway mentioned below refers to the conversion of Modbus RTU to Modbus TCP, and does not involve the processing of Modbus ASCII data frames. Modbus ASCII only supports transparent transmission.
Simple Protocol Conversion
The most conventional and common Modbus gateway function, simple protocol conversion is the most efficient Modbus gateway mode for data processing, it only extracts the key fields in the data, and then encodes the extracted data with another protocol (Modbus RTUßàModbus TCP) to send.
The multi-host gateway can only work in the TCP server mode, and can process multiple Modbus TCP host requests at the same time. The serial port server receives other host requests when one host request is not completed. At this time, the serial port server will perform on the RS485 bus. Arbitration output (in layman's terms, it blocks subsequent instructions)
The first thing to understand is that the communication rate of the serial port is much lower than that of the network port. When the host requests the RTU device, it usually only processes a few registers. The "storage gateway" is used in this working environment.
In order to solve the problem of slow return of the first command of the "storage" gateway, a configuration gateway can be used. The configuration gateway also adopts the method of obtaining the contents of the registers of the RS485 bus slave station by querying the "storage" gateway in advance. In order to solve the problem of slow return of the first instruction, the required register list must be configured inside the gateway in advance.
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