ATEN ALTUSEN PN9108U User Manual download pdf (Page 37)

Chapter 5. Port Operating Modes

UDP Mode

UDP (User Datagram Protocol) Mode is faster and more efficient at

communications than TCP. In UDP mode, communications are bilateral. A

serial device can send data to, and receive data from, up to 16 host computers

via the SN3101’s COM port.

Because it doesn’t perform error checking in the thorough way that TCP does,

UDP is more suitable for real time applications (such as message display) than

the slower TCP which is optimized for data accuracy.

Modbus

Modbus follows a Master/Slave model that allows communication between

many serial devices connected to the same network. It is often used to connect

a supervisory computer with a remote terminal unit (RTU) in supervisory

control and data acquisition (SCADA) systems.

In Modbus mode, the SN3101 acts as a gateway to link individual serial

Modbus devices. Acting as a Modbus master, the SN3101 initiates transactions

and the slaves respond with the requested data. Because it communicates using

TCP over the Internet, the SN3101 eliminates the distance limitations of

traditional Modbus serial communications.

Note: Modbus RTU and Modbus ASCII slave modes support the Direct

Access function (see Direct Access, page 46, for details).

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ATEN ALTUSEN PN9108U User Manual Page 37