Serial Comms Links
17 of 82
Publication S703E V1.1
Issue 06/09
3.2 When to Use RS232
When the host PLC or DCS is located near to the Pakscan P3F master station, RS232 comms can be
used with single point to point links. Either Port 1 or Port 2 can be used, though most users would use
Port 1. Two links can be used if redundant communications are required.
For RS232 on -
Port Terminations
RS232
RS485
Port 1
Off (Down)
RS232 (Down)
Port 2
Off (Down)
RS232 (Down)
3.3 When to Use RS485
When there are several Pakscan P3F master stations to be connected to the PLC, or the distance
between the Host and the master station is more than 20 metres, an RS485 highway will be best. The
highway will require a multi-drop configuration, as shown on the diagram. The screw connectors in
Fig 13: RS232, dual highway, from P3F master station to PLC
Fig 14: RS485, dual highway, from P3F master stations to PLC
PLC
Pakscan P3F Master Station
Pakscan
P
3
rotork
P
3
F
Highway 1 – RS232
Highway 2 – RS232
Pakscan P3F Master Stations
Highway 2 - RS485
Highway 1 - RS485
PLC
Pakscan
P
3
rotork
P
3
F
Pakscan
P
3
rotork
P
3
F
