Additional Installation Tip s
7.7 CableandBusTerminationRS-485
• If maximum transfer d istance and maximum transfer speed is needed,
shielded and twisted pair cable should be used. The mutual capacitance
may not exceed 52.5 pF/m, and the cable area should be at least 0.25 mm
2
(AWG 24).
• 0 V, the reference voltage for c ommunication should be included in
the cabling. With two-way communication use two pairs; one pair for
communication and one pair for 0 V.
• The shield must be grounded at one end. The other end i s u sually grounded,
but with longer distances or when there is a difference in the ground potential,
theshieldshouldbeconnectedtothegroundvia0.1μF/250Vfilmcapacitor
to prevent ground current in the braided shield. A number of manufacturers
recommendthattheshieldbegroundedateachnode. Variousmanufacturers
have different systems for bus termination.
Depending on the recipients’ design, the bus wires may be on the same level or
require pull-up or pull-down to e nsure that no faulty signals are detected when the
bus i s in resting mode (all transmitters are disconnected).
7.8 USBMemorystick
TheUSBportsonX2basev2areof2.0standard. EventhoughUSB3.0maywork
well, we recommend to use USB memory sticks dedicated for USB 2.0.
BeijerElectronics, MAEN330
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