Rockwell Automation T8153 Trusted Communications Interface Adaptor - Manual (Page 10)

Trusted
TM
Communication Interface Adaptor T8153
Issue 12 Apr 10 PD-T8153 10
If the Termination Assembly is the last device in the chain Connector 1 is used and both the TX
Termination Link and the TX/RX Termination Link are fitted. The TX Termination link is used here so
that both ends of the line with multiple transmitters connected are terminated.
RS485 Half Duplex Multiplexed
This is the 2 wire 485 system that is only wired on the RX/TX wires.
If the Termination Assembly is at the start or end of the transmission line Connector 1 is used and the
TX/RX Termination link is fitted.
If the Termination Assembly is in the transmission line then Connector 1 is used to connect the chain in
and Connector 2 is used to wire out to the next device. No Links are fitted for this port.
2.4. RS485 Hints
The signal ground on the RS485 links must always be connected otherwise the communications
between the devices may be unreliable. When specifying cable for these connections allowance should
be made for the signal ground connection. If screened cable is used the signal ground should not be
connected to the screen. It is usual to connect the screen to the chassis earth at one end only.
Some manufacturers tend to use + and – designations on their equipment for labelling the pairs. Since
there is no standard as to how these match up with the EIA circuit designators the following may be
useful:
With the transmission line in the ‘Idle’ or ‘Off’ state connect a multimeter on the volts range across the
pair. When the multimeter reads a negative voltage the +ve terminal of the multimeter is connected to
A and the –ve terminal is connected to B.
2.5. Ethernet ports
Ethernet ports 1 (TCP/IP 0) on J6 and 2 (TCP/IP 1) on J8 are provided with connections to
10/100BaseT networks via RJ45 connectors.