Dataforth SCM9B-D192 Series Manuale d'uso - Pagina 5

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5 SCM9B-D192 USERS MANUAL

An RS-485 repeater is necessary to extend the length of an RS-485

network, or connect more than 32 RS-485 devices on an RS-485

network.

The SCM9B-D192 repeater contains a seven-pin screw terminal plug.

The pin designations are located on the label of each module. The screw

terminals will accept up to #14 gauge wire (AWG). This connector is used

for +5.0Vdc regulated power supply input and both pairs of RS-485 data

lines. The isolated RS-485 input data lines are clearly marked and their

ground reference is isolated by up to 500VRMS from the power supply

ground. The isolated RS-485 input data lines should be attached to the

end of an existing RS-485 network. The serial data received on the

isolated RS-485 input data lines will be re-amplified and retransmitted on

the RS-485 OUT data lines.

Figure 1 Connections for SCM9B-D192.

BAUD RATE

The SCM9B-D192 contains a 10-position DIP switch located on the

bottom of each unit. The DIP switch is used to select the correct

communications baud rate and must be set to the same value as the

devices connected to the RS-485 data lines. Each position on the DIP

switch is labeled from 1 to 10. Switch position 1 selects 300 baud. Switch

positions 2 thru 9 select standard baud rates from 600 to 57.6K

respectively. Switch position10 selects 115.2K baud rate. Only one baud

rate switch may be turned on (up position) at one time for proper

operation.

RS-485 TERMINATIONS

The proper termination techniques for any RS-485 system require two

biasing resistors and two termination resistors. The 1kΩ biasing resistors

are connected from the DATA line to +5Vdc and from the DATA* line to

RS-485

Output

RS-485

Input