Dataforth SCM9B-D192 Series User manual

SCM9B-D192
USERS MANUAL
REVISED: 07-26-18
Dataforth Corporation
3331 E. Hemisphere Loop
Tucson, AZ 85706
The information in this publication has been carefully checked and is
believed to be accurate; however, no responsibility is assumed for
possible inaccuracies or omissions. Applications information in this
manual is intended as suggestions for possible use of the products and
not as explicit performance in a specific application. Specifications may be
subject to change without notice.

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WARRANTY
DATAFORTH warrants each SCM9B-D192 series module to be free from
defects in materials and workmanship under normal conditions of use and
service and will replace any component found to be defective, on its
return to DATAFORTH, transportation charges prepaid within one year of
its original purchase. DATAFORTH assumes no liability, expressed or
implied, beyond its obligation to replace any component involved. Such
warranty is in lieu of all other warranties expressed or implied.
RETURNS
When returning products for any reason, contact the factory and request
a Return Authorization Number and shipping instructions. Write the
Return Authorization Number on the outside of the shipping box.
DATAFORTH strongly recommends that you insure the product for value
prior to shipping. Items should not be returned collect, as they will not be
accepted.

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GENERAL DESCRIPTION
The RS-485 communications standard is recommended when many
modules, or other addressable devices, must be connected to a host
computer over long distances. The SCM9B-D192 repeaters allow
communications bus lengths up to 4,000 feet and baud rates up to
115K baud using one twisted pair of wires. The SCM9B-D192 is an RS-
485 repeater. Repeaters are required to extend communications bus
lengths or allow more than 32 RS-485 devices to be connected to a
communications bus. A repeater simply re-amplifies, or boosts, existing
RS-485 signals transmitted over long distances.
The SCM9B-D192 is isolated between input and output ports and
requires a regulated +5Vdc power supply.

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SPECIFICATIONS
Max common mode voltage: 500Vrms, 60s duration.
Baud rates: 300, 600, 1200, 2400, 4800, 9600, 19200,
38400, 57600, 115200 (Dip -switch selectable).
Temperature range (operating & storage): -25 to +70°C.
Relative humidity: 0 - 95% noncondensing.
Warranty: 3 years on workmanship and materials.
Power Specifications
Power requirements: Regulated +5Vdc.
Power consumption: 1.0W Max (RS-485 driver on).
MECHANICALS AND DIMENSIONS
Case: ABS case with screw terminal barrier plug (supplied.
RS-485 Connectors: Phoenix screw terminal barrier plug (supplied).
Replace with Phoenix MSTB 2.5/4 ST 5.08 or equivalent. Warranty:
3 years on workmanship and materials.

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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 1kΩbiasing resistors
are connected from the DATA line to +5Vdc and from the DATA* line to
RS-485
Output
RS-485
Input

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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 220Ωresistors 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.

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FACTORY RS-485 TERMINATION SETTINGS
Each SCM9B-D192 contains internal pin strips for enabling the internal
termination and biasing resistors. Each pc board is clearly marked with the
jumper designators adjacent to each row of pins. The jumper designators
are +1K, 220 and -1K. To enable any resistor, place a jumper over the
pins next to the required designator. The factory switch and jumper
settings are outlined below.
SCM9B-D192:
Baud Rate: 300 baud switch up.
RS-485 (J3): Biasing Resistors: +1K, -1K jumpers installed.
Termination Resistor: 220 jumper installed.
Isolated RS-485 (J2): Biasing Resistors: +1K, -1K jumpers installed.
Termination Resistor: 220 jumper not installed.