Contemporary Control Systems BASrouterLX Installation Guide - Manual (Page 10)

TD120100-0IC
10
NOTE: If using shielded cable, connect to chassis at only one point. Wire size
may be dictated by electrical codes for the area where the equipment is being
installed. Consult local regulations.
Observe in Table 1 that 10BASE-T segments can successfully use Category 3, 4
or 5 cable — however, 100BASE-TX segments must use Category 5 cable.
Category 5e cable is highly recommended as the minimum for new installations.
The Ethernet port of the router employs Auto-MDIX technology so either straight-
through or crossover cables can be used to connect to the network.
MS/TP PORT
This port uses an isolated EIA-485 transceiver connected to a 5-pin removable
connector. The transceiver + and – lines tie to + and – pins of the connector. The
SC pin ties to the transceiver ground. You MUST connect the SC pin to the
MS/TP segment signal common — or EIA-485 communication will fail!
In Figure 10 a simplified schematic of the isolated EIA-485 transceiver is shown.
Notice that the transceiver common (SC) is electrically isolated from the router
power supply common (COM) through the use of opto-isolators and an isolated
DC-DC converter. An isolated EIA-485 transceiver offers less chance of damage
to the transceiver from high common-mode voltages, but there is still a risk. Surge
suppression is applied between the two differential inputs and between each input
and ground. Since the transceiver is electrically isolated, the transceiver circuit
common must be brought out for connection to the other devices on the EIA-485
network. This is accomplished by pin SC. The differential pair is labelled + and
– and requires a three-wire connection to the EIA-485 network. Connecting other
isolated EIA-485 devices is no problem since each device requires a 3-wire
connection. Just make corresponding connections. For non-isolated EIA-485
devices, usually only a 2-wire connection is provided. The third wire is the power
supply common. In this situation, the SC connection MUST be made to the power
supply common of the non-isolated device. Refer to the device vendor
instructions for connecting such a device.
In an application where one connection is made to Ethernet and the other to EIA-
485, the location of the router is probably at the end of the EIA-485 bus segment
and therefore both bias and termination must be applied to the segment end. The
product is shipped with bias and termination applied, but this can be changed by
removing three jumpers. This should be done if the router is to be connected
anywhere between the end EIA-485 devices.
The router can address up to 31 MS/TP full-load or 62 half-load devices on the
local bus at baud rates from 9.6 to 115.2 kbps.
EIA-485 Bias and Termination Jumpers