Contemporary Controls ARCNET USB22-4000 Manuale di installazione - Pagina 5

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-TB5 Twisted-pair Bus

The -TB5 transceiver accommodates twisted-pair cabling via a pair of

RJ-45 jacks which allow the unit to be daisy-chained at any location on

the bus segment Usually IBM type 3 unshielded twisted-pair cable

(UTP) is used, but shielded cable (STP) can also be used to provide

continuous shielding between devices.

When the USB22-TB5 is located at the end of a bus segment, Apply the

provided 100-ohm terminator to the empty RJ-45 jack to match the cable

impedance.

-485 DC-Coupled EIA-485

Dual RJ-45 jacks are provided for each DC-coupled EIA-485 segment.

A DC-coupled segment can be up to 900 feet of IBM type 3 (or better)

STP or UTP cable, and as many as 17 nodes can occupy a segment.

Make sure the phase integrity of the wiring remains consistent

throughout the network. All phase A signals on NIMs and hubs must

connect together. The same applies to phase B. Refer to Figure 1 for

connector wiring.

Termination

When the USB22-485 is located at the end of a bus segment, apply the

provided 100-ohm terminator to the empty RJ-45 jack.

Bias

Bias must also be applied to the network to prevent the differential

receivers from assuming invalid logic states when the signal line is

floated. Bias is provided on the USB22-485 by a set of 806-ohm pull-up

and pull-down resistors. Refer to the existing NIM user manual for a

discussion of bias requirements.

Ground

All devices on the segment should be referenced to the same ground

potential to achieve the common mode voltage (+/–7 Vdc) required for

the EIA-485 specification. A ground connection is not provided by the

USB22-485.

It is assumed adequate grounding is supplied by the

existing equipment. Refer to the existing equipment user manual for a

discussion of grounding requirements.

TD040900-0IE