GE P485 instruction manual Sub-network data flow

SOFTWARE OVERVIEW

SUB-NETWORKThe second step in the configuration wizard selects the properties for the Modbus sub- PROPERTIES network. The data flow for the sub-network is shown below.

Fieldbus

Master

			Fieldbus
Data Direction
In	Out		GE
		Converter

Modbus

Sub-Network

Figure 4-2: Sub-network data flow

Refer to the particular sub-network device manual(s) to determine the appropriate settings and communication options. If multiple devices are being installed on the same sub- network, they must be configurable for a common set of communication parameters.

All numerical values are entered and shown in decimal unless otherwise specified.

The sub-network properties window is shown below.

NOTE

•Physical standard: The physical standard can be either RS232, RS485, or RS422.

RS232 is a point-to-point communication standard; that is, it is only possible to have one sub-network node (Modbus device) connected to the P485 converter when using RS232. RS232 supports a maximum cable length of 15 meters and is full duplex. It uses two signal lines (Rx and Tx) and the signal is measured relative to ground.

RS485 is a common multi-drop communication standard. It is used with larger cable distances with one or several sub-network nodes (Modbus devices) connected. RS485 supports a maximum of 31 nodes, with half duplex and a total cable length up to 1200 meters. It uses two signal lines (A-line and B-line, twisted pair) with the signal being measured between the two lines.

RS422 is a common multi-drop communication standard. It is used with larger cable distances with one or several sub-network nodes connected. RS422 supports a maximum of 31 nodes, with full duplex and a total cable length up to 1200 meters. It uses four signal lines (receive A1-B1 and transmit A2-B2, twisted pair) with the signals being measured between the two signal lines A and B.

•Bitrate (bits/s): This parameters refers to the speed of the sub-network. Speeds are 1200 to 57600 bps in predefined steps. The bitrate is also referred to as baud rate.

4–4 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE