Modbus TCP/IP to RTU Gateway

The NL200/201 can serve as a Modbus TCP/IP to RTU Gateway. It will listen for incoming Modbus TCP/IP connections from a Modbus TCP/IP client (formerly called master). The port number of the listening connection is specified in the RS-232 (or CS I/O) Service Port setting and is typically set to a value of 502. The NL200/201 will convert incoming Modbus TCP/IP frames to Modbus RTU and forward them to the RS-232 (or CS I/O) port. The NL200/201 will wait for a response from the Modbus RTU device and forward that response back to the remote Modbus TCP/IP client over the established TCP connection. The Modbus RTU device is generally a data logger connected to the RS-232 (or CS I/O) port or a data logger located remotely over a transparent radio (for example, RF452/RF451/RF450) connection, but can be any Modbus RTU device. When the NL200/201 is connected directly to a CR800 series, CR1000, or CR3000 being polled by a Modbus TCP/IP client, the NL200/201 is most commonly configured with bridge mode enabled instead of as a Modbus TCP/IP to RTU Gateway.