Moxa TCC-100-T Guide de l'utilisateur télécharger pdf (Page 17)

Installation

Termination Resistor Diagram

Termination is designed to

mitigate noise from the

RS-422/485 transmission

signals. If the network cable is

too long, undesirable

transmission-line effects will

arise. The best method for

mitigating energy on an unused

conductor is to dissipate the

RxD+

RxD-

Termination Resistor:

S3 On to Enable

S3 Off to Disable

energy as heat by terminating both ends of the unused conductor to ground with

resistors (so-called bi-directional termination). The resistance of the resistors

should be equal to the characteristic impedance of the line. The most common

RS-485 twisted pair has a characteristic impendence of 100-120 Ohm. Moxa’s

termination technique is bi-directional termination, which offers excellent signal

integrity. With this technique, the line drivers can be located anywhere on the

network.

Function Diagram

TxD

RxD

RTS

CTS

GND

TxD+

TxD

RxD+ (Data +)

RxD

(Data

)

RS-232

Line Driver

Isolation

RS-422/485

Line Driver

Communication

Controller

ADDC

Logic

RS-485

RS-422

2-7

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Moxa TCC-100-T Guide de l'utilisateur Page 17

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