GE P485 - Manual (Page 26)

4–4 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
SOFTWARE OVERVIEW
SUB-NETWORK
PROPERTIES
The second step in the configuration wizard selects the properties for the Modbus sub-
network. The data flow for the sub-network is shown below.
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.
• 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.
Fieldbus
Master
Modbus
Sub-Network
Fieldbus
GE
Converter
Data Direction
In Out
NOTE