Ediseja 21 CMU 200 Manuel d'utilisateur télécharger pdf (Page 10)

CMU 100 - Star coupler

Cable

CMU100 / RS232 to PC / RS232

CMU100

DB9 F pin Signal

Direction PC

Signal DB9 F pin

2 RX <------- TX 3

3 TX -------> RX 2

5 GND <-------> GND 5

RS485 INTERFACE BOARD

Description

Single, galvanically isolated, half duplex, RS485 port with Phoenix 3 pin screw connector.

Automatic switch to receive after end of transmission with additional terminating and

stabilizating resistors.

Hardware settings

For proper functioning of that board some settings must be done:



board address



RS485 bus termination and stabilisation



baud rate

RS485 bus termination and stabilisation

TERMINATION

At high transmission rates or long distance, RS485 bus termination is necessery.

The termination on RS485 bus must be set on both ends of the RS485 bus.

STABILISATION

Some device, to work properly, demands that RS485 must always be in known and valid state.

That is, when + (positive) pin is more than 200 mV positive than – (negative) pin. Pins + and –

are sometimes marked as A and B. In case that no device on RS485 bus is transmitting or in

case of short circuit, there is no voltage difference between those pins and some device do not

work correctly.

On this port board so called „true fail-safe“ RS485 chip is used so board works correctly without

stabilisation at invalid RS485 bus state. But still switches for stabilisation are provided on port

board.

The stabilization on RS485 bus may be set on one device only!

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Ediseja 21 CMU 200 Manuel d'utilisateur Page 10