B&B Electronics 485LDRC - Datasheet User Manual
Produ ct info rmati o n b&b e lectr on ics, Introduction, Leds
485LDRC-0812-1/3
© 2003 by B&B Electronics. All rights reserved.
www.bb-elec.com [email protected] [email protected]
International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104
European Office: Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445
PRODU
CT INFO
RMATI
O
N
B&B E
LECTR
ON
ICS
Models 485DRC and 485LDRC
Industrial DIN Rail Mounted
Optically Isolated RS-232
to
RS-422/485 Converters
With Surge Suppression
Introduction
The DIN Rail mountable Models 485DRC and 485LDRC optically isolate and convert unbalanced, full or half-duplex
RS-232 signals to optically isolated, balanced, full or half-duplex RS-422 or RS-485 signals at baud rates up to 115.2
kbps. These units also surge suppress the RS-422/485 lines. They feature Send Data Control circuitry so no software
control of handshake lines is required in RS-485 mode.
LEDs
The 485LDRC
includes all the above features plus 3 LED’s: one indicating RS-485 Transmit Data, one for RS-485
Receive Data, and one for power.
Description
The 485DRC/485LDRC has screw down terminal blocks on the RS-232 side and the RS-422/RS-485 side. Transmit
(TD), Receive (RD) and Ground are supported on the RS-232 side. The unit is powered by a supply voltage of 10 to
30VDC on the RS-232 side, useful where 24VDC is commonly found. Transmit Data A (-), Transmit Data B (+), Receive
Data A (-), Receive Data B (+), and Ground are supported on the RS-422/RS-485 side. Communication features on the
485DRC/485LDRC are dipswitch selectable on the unit.
RS-485 Mode with Send Data Control
Send Data Control recognizes the first bit of data from the RS-232 side, enables the transmitter and disables the
receiver. After the last bit of data is sent from the RS-232 side, the timeout waits one character length, then disables the
transmitter and enables the receiver. The timeout can be selected with dipswitches or by changing the value of R11 (see
Table 2). If the system requires the line to be “turned around” faster, i.e. the slave device starts responding before the
transmitter of the 485DRC/485LDRC is disabled, R11 can be changed to meet the specific baud rate. Termination
resistance can be selected with Switch 5 for high baud rates and long cable distances. See B&B Electronics’ RS-422/485
Application Note available on the website or by mail. Factory setting: 9600 baud.
Table 1. Typical Communication Setups
Switch 1
TX Enable
Switch 2
RX Enable
Switch 3
2/4 Wire
Switch 4
2/4 Wire
RS-485 2-Wire Mode
(half-duplex)
ON
ON
ON
ON
RS-485 4-Wire Mode
(full-duplex)
ON
OFF
OFF
OFF
RS-422 Mode
(full-duplex)
OFF
OFF
OFF
OFF
Table 2. Baud Rate Selection
Switch
6
Switch
7
Switch
8
R11
Time (ms)
1200
OFF
OFF
OFF
820k
8.33
2400
OFF
OFF
ON
Not Used
4.16
4800
OFF
ON
OFF
Not Used
2.08
9600
ON
OFF
OFF
Not Used
1.04
19200
ON
ON
ON
Not Used
.580
38400
OFF
OFF
OFF
27k
.260
57600
OFF
OFF
OFF
16k
.176
115200
OFF
OFF
OFF
8.2k
.0868
In a two-wire setup, switches
3 & 4 should be “ON”, making terminal block (G)
the Data (
–) line and terminal block (H) the Data (+) line.
TYPICAL TWO-WIRE RS-485 SETUP
Generator
Receiver
Circuit ground
DATA +
(TERMINAL BLOCK H)
GND
(TERMINAL BLOCK M)
DATA -
(TERMINAL BLOCK G)
G
R
Rt
B
G
A
R
B
A
RX
TX
485DRC/485LDRC
TYPICAL RS-422/485 4 WIRE
SETUP
GND
(TERMINAL BLOCK M)
TD A -
(TERMINAL BLOCK G)
TD B +
(TERMINAL BLOCK H)
RD A -
(TERMINAL BLOCK K)
RD B +
(TERMINAL BLOCK L)
Receiver
Circuit ground
Generator
R
G
R
Rt
Rt
B
A
A
B
ENABLE
G
RX
TX
485DRC/485LDRC