Datasheet

p/n 7207r4 485DRCI-0812ds page 3/5
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PRODUCT INFORMATION B&B ELECTRONICS
RS-422/485 Terminal
Block
Terminal
RS-485 2-Wire
RS-422/485 4-Wire
A
GND
GND
B
Data B(+)
RDB(+)
C
Data A(-)
RDA(-)
D
---
TDB(+)
E
---
TDA(-)
DIN Rail Mounting
1. Angle the top portion of the DIN mount over the top of
DIN Rail.
2. Move the converter so that it is parallel with the DIN
Rail.
3. Snap the bottom of the DIN mount in place.
RS-422/485 Baud / Timeout
Switch Selectable
Baud
SW1
SW1
SW1
SW1
SW1
Timeout
(Kbps)
8
9
10
11
12
(ms)
2.4
ON
OFF
OFF
OFF
OFF
4.16
4.8
OFF
ON
OFF
OFF
OFF
2.08
9.6
OFF
OFF
ON
OFF
OFF
1.04
19.2
OFF
OFF
OFF
ON
OFF
0.580
38.4
OFF
OFF
OFF
OFF
ON
0.260
Resistor Selectable
Baud
Timeout
(Kbps)
SW1-8 through 12
R-11 Value
(ms)
1.2
OFF
820 KΩ
8.33
57.6
OFF
16 KΩ
0.176
115.2
OFF
8.2 KΩ
0.087
1. Pre-defined baud rates are set using SW1 positions 8
through 12.
2. Resistor Selectable baud rates are set by inserting a
through-hole resistor (R-11) on the circuit board.
3. WARNING – EXPLOSION HAZARD: SUBSTITUTION
OF COMPONENTS MAY IMPAIR SUITABILITY FOR
CLASS 1, DIVISION 2.
RS-485 2-Wire
(Half Duplex)
1. Loosen the screws to open the TB lead clamps for the
A, B, and C terminals.
2. Insert the RS-485 2-Wire signal leads. The terminal
board accepts 28 to 14 AWG wire.
3. Tighten the screws to close the TB lead clamps.
Ensure the clamps hold the leads securely. However,
do not over tighten. For Class 1 DIV 2 installations,
ensure the wiring is in accordance with the special
precautions and the specification table.
4. Configure the DIP Switch on the bottom of the
converter for RS-485 2-Wire operation (see above).
X. ON = Termination IN
OFF=Termination OUT
Y. ON=TX Bias IN
OFF=TX Bias OUT
Z. ON=RX Bias IN
OFF=RX Bias OUT
Installation Notes:
In 2-Wire mode, Terminal B is tied to Terminal D
and Terminal C is tied to Terminal E with DIP
Switch SW1-3 and SW1-4.
If Termination is required, a 120Ω resistor can be
placed across the D and E terminals by setting
SW1-5 to ON.
This converter has 1.2 KΩ pull-up/down bias
resistors built in. To use this bias, set SW1-6 and
SW1-7 to ON.
B&B Electronics’ RS-485 Application Note contains
more information about termination and biasing.
This reference is available on our web site.