6 SCM9B-D192 USERS MANUAL
ground. The biasing resistors and are normally positioned at the HOST
end of the cable. The RS-485 standard also requires two resistors across
the data lines for proper termination. Two 220
Ω
resistors should be
connected between the DATA and DATA* lines. The resistors 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-D192 contains the biasing and termination resistors
necessary to interface any equipment on an RS-485 network. These
resistors are jumper-selectable making it easier to interface the SCM9B-
D192 to other pieces of equipment that may or may not contain the
biasing and/or termination resistors.
RS-485 TERMINATION & BIASING SETTINGS
Proper termination and biasing of any RS-485 based system can be
performed by properly enabling the correct resistors inside each SCM9B-
D192. Figures 2.0 shows the location of the jumpers on the printed
circuit board. The jumpers are shown in their factory set locations to
enable the selected resistors. Insert or remove the jumpers as required to
properly terminate any RS-485 system.
FIGURE 2. SCM9B-D192 jumper locations.
