For an explanation of RS-485 termination and biasing requirements,
refer to Advantech’s RS-422/485 Application Note. This publication
can be downloaded at:
www.advantech.com
Switch position 8 is not used.
Set the DIP Switches
2
COMMUNICATIONS MODE
Switch
1
2
3
4
RS-485 2-Wire Half-Duplex
ON
ON
ON
ON
RS-485 4-Wire Full-Duplex
ON
OFF
OFF
OFF
RS-422 Full-Duplex
OFF
OFF
OFF
OFF
BUILT-IN TERMINATION RESISTOR
SWITCH
5
Use Built-in 120Ω Termination
ON
Use External or No Termination
OFF
Data
LEDs
Power
LED
DB9
Port
Data
LEDs
Terminal
Block
DIP
Switches
10 to 48 Vdc
1.9 W max.
Grounding the unit is recommended.
Connect a grounding wire from the ground lug
to a good source of Earth Ground.
Ground
Lug
BUILT-IN TRANSMIT BIAS RESISTOR SWITCH
6
Use External or No Bias Resistor
ON
Use Built-in 1.2KΩ Transmit Bias Resistor
OFF
BUILT-IN RECEIVE BIAS RESISTOR
SWITCH
7
Use External or No Bias Resistor
ON
Use Built-in 1.2KΩ Receive Bias Resistor
OFF
TERMINAL RS-485 2-WIRE
RS-422/485 4-WIRE
A
***
TDA (-)
B
***
TDB (+)
C
Data A (-)
RDA (-)
D
Data B (+)
RDB (+)
E
GND
GND
DIP SWITCH RS-422/485 4-WIRE
1
2
3
4
5
6
7
ON/OFF
OFF
OFF
OFF
***
***
***
Position 1 = ON for RS-485, OFF for RS-422.
Positions 5, 6, 7 are used for termination and biasing.
DIP SWITCH RS-485 2-WIRE
1
2
3
4
5
6
7
ON
ON
ON
ON
x
x
x
Positions 5, 6, 7 are used for termination and biasing.
•
Configure for RS-485 four-wire.
• Jumper terminals A to C and B to D.
• Connect a PC to the RS-232 port (see Step 3).
• Using HyperTerminal or a similar program, con-
nect to the appropriate COM port.
•
Turn off HyperTerminal local Echo.
• Transmit data. The same data should be re-
turned. When data is sent and looped back, the
TD and RD LEDs will blink on both ports.
LEDs
Power LED
Red = ON when power is applied.
Data LEDs
Green = LEDs flash when data is present on port.
+
+
Wiring Converter & Device
3
Loopback Test
4
Check LEDs
5
Product Overview
1
DB9 PINOUTS
PIN
SIGNAL DIRECTION
1
DCD
***
2
RD
Output
3
TD
Input
4
DTR
***
5
GND
***
6
DSR
**
7
RTS
***
8
CTS
***
9
RI
***
TERMINAL BLOCK
POSITION
SIGNAL
A
Ground
B
RDB (+)
C
RDA (-)
D
TDB (+)
E
TDA (-)
RS-485 2-Wire
RS-485/422 4-Wire
Your Device
Your Device
BB-485DRCi
BB-485DRCi
A
DATA
B (+)
DATA
A (-)
GND
TDA
(-)
C
D
E
B
A
C
D
E
B
TDB
(+)
RDB
(+)
RDA
(-)
GND
