B&B Electronics 485DSS User Manual

Distributed Smart Switch

Model 485DSS

Documentation Number 485DSS-0308

This product

Designed and Manufactured

In Ottawa, Illinois

of domestic and imported parts by

B&B Electronics Mfg. Co. Inc.

707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350

PH [phone] -- FAX [phone]

http://www.bb-elec.com

[e-mail]

[e-mail]

USA

Internet:

© 1998 B&B Electronics -- January 2008

485DSS-0308 Manual Cover Page

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

TABLE OF CONTENTS

CHAPTER 1: HARDWARE ................................................................... 1

NTRODUCTION ........................................................................................ 1

I

Figure 1. Example of an RS-485/422 Multi-Node Network ...................... 1

CHECKLIST ............................................................................................... 1

PECIFICATIONS ....................................................................................... 2

S

Figure 2. Top View of Circuit Board .......................................................... 2

PORT CONFIGURATION ............................................................................. 2

RS-485/422 Port .................................................................................. 2

Table 1. RS-422/485 Port ...................................................................... 3

RS-232 Port ......................................................................................... 3

Table 2. RS-232 DTE DB25P Connector Chart .................................... 4

RS-422/485 Wiring .............................................................................. 4

2-Wire Mode ........................................................................................ 4

Table 3. Component Values For Send Data Timing .............................. 5

Figure 3. RS-485 Wiring Diagram ............................................................. 6

4-Wire Mode ........................................................................................ 6

Figure 4. RS-422 Wiring Diagram ............................................................. 7

RS-485 AND RS-422 TERMINATION ......................................................... 7

OWER SUPPLY ........................................................................................ 7

P

PERATION .............................................................................................. 8

O

Figure 5. Simplified Functional Diagram .................................................. 9

COMMUNICATION CONFIGURATION ......................................................... 9

ISTRIBUTED SMART SWITCH COMMANDS .............................................. 9

D

The Command String ......................................................................... 10

ON Command .................................................................................... 10

OFF Command .................................................................................. 11

STATUS REQUEST Command ......................................................... 11

ETTING THE 485DSS ADDRESS ............................................................ 14

S

Table 4. Address Switch ...................................................................... 14

BINARY FILE TRANSFER ......................................................................... 15

CHAPTER 2: SOFTWARE .................................................................. 16

D

ESCRIPTION ........................................................................................ 16

APPENDIX A: ASCII CHARACTER CODES ................................ A-1

APPENDIX B: DECIMAL/HEXADECIMAL CONVERSIONS ..... B-1

Table 5. Hex/Dec Conversions ............................................................... B-1

APPENDIX C: CABLE CHARTS ...................................................... C-1

485DSS-0308 Manual Table of Contents i

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

HART 1. IBM PC DB25 CONNECTOR TO ........................................... C-1

C

485DSS RS-232 (DTE) PORT............................................................ C-1

HART 3. RS-232 DCE DEVICE W/DB25 CONNECTOR TO .................. C-1

C

485DSS RS-232 (DTE) PORT............................................................ C-1

HART 2. IBM PC DB9 CONNECTOR TO ............................................. C-1

C

485DSS RS-232 (DTE) PORT............................................................ C-1

HART 4. RS-232 DCE DEVICE W/DB9 CONNECTOR TO .................... C-2

C

485DSS RS-232 (DTE) PORT............................................................ C-2

HART 5. RS-422/485 4-WIRE DEVICE TO 485DSS RS-422/485 PORT C-2

C

HART 6. RS-485 2-WIRE DEVICE TO 485DSS RS-485/422 PORT. .... C-2

C

ii Table of Contents 485DSS-0308 Manual

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

Chapter 1: HARDWARE
Introduction

The RS-485 Distributed Smart Switch (485DSS) connects one
RS-232 device to an RS-485 multi-node network as shown in Figure

1. To accomplish this, the 485DSS converts RS-232 to an
addressable RS-485 node. A unique address, from 0 to 255, is user
assigned by setting switches on the 485DSS.

Figure 1. Example of an RS-485/422 Multi-Node Network

Checklist

The following items should be in the shipping carton:

1. RS-485 Distributed Smart Switch

2. Instruction Manual

3. Software
Contact the shippers immediately if any of the items above is
missing or has damage.

485DSS-0308 Manual 1

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

Specifications

Model: 485DSS
Size: 4.8"L x 2.15"W x 0.9"H
Power: +11 to 16 Vdc 75mA
RS-232 Connection: DB-25 male (DTE configured)
RS-485 Connection: Terminal Blocks
Communications: 9600 baud, no parity, 8 data bits, 1 stop bit

Figure 2. Top View of Circuit Board

Port Configuration

The 485DSS has a RS-485/422 port and a RS-232 port. The
RS-485/422 signals are on terminal blocks. Table 1 shows you the
pinouts and Figure 2 shows you the location of the terminal blocks.
The RS-232 signal, in the DTE configuration, connects to a DB25
male connector. Table 2 shows you the RS-232 pinouts.

RS-485/422 Port

The RS-485 port on the 485DSS receives and transmits data to
and from the RS-485 network. The RS-485 port has a balanced
differential line driver and receiver. RS-485 allows up to 32 driver
and receiver pairs to share a two-wire party line network. This port
will operate on a 4-wire network and is compatible with RS-422
devices. Refer to B&B Electronics’ free RS-422/485 Application Note
for more information. Refer to Appendix C for cable charts.

2 485DSS-0308 Manual

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

Table 1. RS-422/485 Port

Terminal
Block
Signal

Description

RS-422/485
Signal
Direction of
Port

FR GND Frame Ground <------>

TD(A)(-) Transmit Data (A)(-) Output

TD(B)(+) Transmit Data (B)(+) Output

RD(A)(-) Receive Data (A)(-) Input

RD(B)(+) Receive Data (B)(+) Input

GND Signal Ground <------>

+12VDC Power Supply Input

RS-232 Port
The RS-232 DTE port is an asynchronous port that supports TD

and RD signals. In order to make the proper connections to the RS­232 port. It is necessary to have a basic understanding of the terms
DCE and DTE. The original design for connecting RS-232 devices
together uses DB25 connectors, and connects a DTE (Data

Terminal Equipment) device to a DCE (Data Communication
Equipment) device. Each device will have inputs on pins that

correspond to outputs on the same pins of the other device. For
example, a DTE device transmits data out on pin 2 and a DCE
device receives data in on pin 2. IBM PC's are DTE devices and
modems are DCE devices. Only TD and RD of the RS-232 port
pass through to the RS-485 port when the 485DSS is ON. The
485DSS raises and lowers the RTS output signal on the RS-232
port to reflect the connect state of the port. This signal can notify the
RS-232 device to start communicating to the Host or it can be an
alarm output. The Host can monitor the CTS input line to determine
if the RS-232 device is requesting access to the network. This input
line could also be an alarm input. NOTE: If using RTS or CTS lines
as alarms the user may have to design additional circuitry to
properly interface to the alarm circuits. Refer to cable charts in
Appendix C for making your own cables.

485DSS-0308 Manual 3

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]

Table 2. RS-232 DTE DB25P Connector Chart

Pin #

Signal

FR GND Frame Ground <------>

1

TD Transmit Data Output

2

RD Receive Data Input

3

RTS Request to Send Output

4

CTS Clear to Send Input

5

SG Signal Ground <------>

7

Description

Signal
Direction of
RS-232 DTE
Port

RS-422/485 Wiring

RS-485 receivers also have an enable/disable control line. The
2W/4W jumper selects when to enable and disable RS-485 receiver.
Setting the jumper to the 4W position constantly enables the
receiver which is the same as operating in an RS-422/485 4-wire
mode. In this position and connected to a 2-wire network, all data
being transmitted by the RS-485 driver echos back through the RS­485 receiver. Setting the jumper to 2W (RS-485, 2-wire mode)
automatically enables the receiver when the RS-485 driver disables
and visa versa.
To configure the 485DSS for a typical 2-wire party line network,
set the jumper in the 2W position. Refer to Figure 2 for the jumper
location.
The EIA RS-485 Specification labels data lines with an "A" and
"B" designator. Some RS-485 equipment uses a "+" and "-"
designator. In almost all cases, the "A" line is the equivalent of the "­" line and the "B" line is the equivalent of the "+" line. See Figure 3
for a wiring example.

2-Wire Mode

RS-485 allows half-duplex communications of multiple drivers
having a control line for enabling and disabling (tri-stating) their
outputs. When the 485DSS transmits a status reply message to the
Host, the microcontroller will automatically enable the driver before
transmitting the first character of the reply and disable the driver
after the last character of the reply. When the 485DSS is ON
(selected) and the RS-232 device is transmitting data to the Host the
Send Data (SD) control circuit enables and disables the driver. The
485DSS disables the driver when it is not transmitting data to the
Host and listens to (receives) all communications on the network.

4 485DSS-0308 Manual

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]