B&B Electronics 485LDRC Datasheet

© 2003 by B&B Electronics. All rights reserved.

www.bb-elec.com [e-mail] [e-mail]

International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax [phone]

European Office: Westlink Commercial Park Oranmore Co. Galway Ireland [phone] Fax [phone]

PRODUCT INFORMATION B&B ELECTRONICS

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

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

TYPICAL TWO-WIRE RS-485 SETUP

Generator

Receiver

Circuit ground

DATA +

(TERMINAL BLOCK H)

GND

(TERMINAL BLOCK M)

DATA -

(TERMINAL BLOCK G)

G

RRtBGARB

A

RX

TX

485DRC/485LDRC

TYPICAL RS-422/485 4 WIRE

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

AAB

ENABLE

G

RX

TX

485DRC/485LDRC

485LDRC-0812-1/3

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

Table 2. Baud Rate Selection

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.

© 2003 by B&B Electronics. All rights reserved.

www.bb-elec.com [e-mail] [e-mail]

International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax [phone]

European Office: Westlink Commercial Park Oranmore Co. Galway Ireland [phone] Fax [phone]

PRODUCT INFORMATION B&B ELECTRONICS

485LDRC-0812-2/3

Terminal Block Configuration

RS-232

(D) TD (input)
(A) RD (output)
(B) SIG. GND
(F) +10 to 30VDC
(C) PWR. GND

RS-422/485

TDA (G) Tx inverted or (-) (output)
RDA (K) Rx inverted or (-) (input)
TDB (H) Tx non-inverted or (+) (output)
RDB (L) Rx non-inverted or (+) (input)
ISO. GND (M) Isolated RS-422/485 Signal Ground/Common

Switch Settings (UP = ON)

1 - Tx Enable (On for 485 mode. Off for 422 mode.)
2 - Rx Enable (On for 2-wire 485 mode. Off for 4-wire 485 and 422 mode.)
3 - 2/4 Wire (On for 2-wire/half duplex. Off for 4-wire full duplex.)
4 - 2/4 Wire (On for 2-wire. Off for 4-wire.)
5 - Termination Resistors (On for termination. Off for no termination.)
6 - 9600 Baud (On for 9600, Off for others. See Table 2 for additional baud rates.)
7 - 4800 Baud (On for 4800, Off for others. See Table 2 for additional baud rates.)
8 - 2400 Baud (On for 2400, Off for others. See Table 2 for additional baud rates.)