Dataforth SCM9B-A2000 Series Gebruikershandleiding - Pagina 7
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7 SCM9B-A1000 & SCM9B-A2000 USERS MANUAL
should be placed at each end of the RS-485 cable. Please refer to Figure
2 for a typical RS-485 system application.
The SCM9B-A1000 and SCM9B-A2000 each contain the biasing and
termination resistors necessary to interface any equipment on an RS-485
network. These resistors are switch-selectable making it easier to
interface the SCM9B-A1000 and SCM9B-A2000 to other pieces of
equipment that may or may not contain the biasing and/or termination
resistors.
Figure 2. RS-485 biasing & termination resistors.
SCM9B-A1000 RS-485 TERMINATIONS
Each SCM9B-A1000 contains internal RS-485 termination and biasing
resistors for proper termination of a RS-485 system. The resistors are
enabled or disabled via two 3-position DIP switches located on the
SCM9B-A1000
rear panel.
One
three-position
switch
enables
termination resistors for the RS-485 IN (HOST) data lines and the other
switch enables termination of the RS-485 OUT data lines. The three-
positioned DIP switches are located to the left of each RS-485 connector
on the SCM9B-A1000 backpanel. The three positioned switches are
used to enable or disable a 1KΩ pull-up between +5Vdc and the DATA+
line, a 1KΩ pull-down resistor between the DATA- line and ground or a
220 Ω termination resistor between the DATA+ and DATA- lines. Each