Siemens 9700, Installation Instructions Manual, Page: 36 / 45

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♦
Install a ¼ Watt termination resistor between the (+) and (-) terminals of
the device at each end point of a straight-line bus. The resistor should
match the nominal impedance of the RS-485 cable (typically 120 ohms –
consult the manufacturer’s documentation for the cable’s impedance
value).
RS-485 Connection Methods to Avoid
Any device connection that causes a branch in the main RS-485 bus should
be avoided. This includes
star and tee (T) methods. These wiring methods
cause signal reflections that may cause interference. At any connection
point on the RS-485 bus, no more than two cables should be connected.
This includes connection points on instruments, converters, and terminal
strips. Following this guideline ensures that both star and tee connections
are avoided.
Ethernet Connections (X
PRESS
C
ARD
Only)
If you purchased the optional X
PRESS
C
ARD
, one 10Base-T and/or one
10Base-FL Ethernet port will be available, depending on ordering options
specified. Specifications are as follows:
Specification Value
Type (10 Base-T) IEEE 802.3 10Base-T for 10 Mbps base band CSMA/CD LANs
Type (10Base-FL) IEEE 802.3 10Base-FL fiber link
Baud Rate 10 Mbps
Duplex Half
Supported Protocols SEABus, Modbus RTU
Isolation Transformer isolated to 1500 VAC RMS
2
38)
The 10Base-T and 10Base-
FL Ethernet ports cannot be
used simultaneously. If both
are connected, only the
10Base-T port will function.