Installation Guide

Installation Guide

Com’X 200

Wiring of the Modbus Communication Network

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Wiring of the Modbus Communication Network

Chapter 3

Wiring of the Modbus Communication Network

Overview

This section describes how to connect a Com’X 200 on a RS 485 Modbus network with an RJ45 or an open-style connector.

It presents 2 possible network topologies.

What Is in This Chapter?

This chapter contains the following topics:

Topic

Modbus Network Characteristics

Modbus Communication Port Wiring Terminal Characteristics

Wiring the Modbus Network

Page

28

31

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27

Wiring of the Modbus Communication Network

Modbus Network Characteristics

Overview

The Modbus over Serial Line Specification and Implementation Guide, published on www.modbus.org, defines the characteristics of the Modbus protocol over serial line. The Com’X 200 complies with this specification.

Modbus Network Standard Diagram

The standard diagram corresponds to the Modbus specification on the www.modbus.org site and in particular to the 2-wire multidrop serial bus diagram.

The simplified diagram is as follows:

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Wiring of the Modbus Communication Network

Characteristics for Connection to the RS 485 Bus

The RS 485 standard allows variants of some characteristics:

 polarization line terminator

 number of slaves bus length

Characteristics

Maximum number of slaves

(without repeater)

Type of trunk cable

Standard Value

32 slaves

Single, shielded, twisted-pair cable, with

120

Ω characteristic impedance, and at least a third conductor

Maximum bus length 1,300 m (4,300 ft) at 19,200 Baud

Maximum length of tap-offs Depends on the transmission rate

Bus polarization

A 450...650

Ω pull-up resistor at the

5 V

A 450...650

Ω pull-down resistor at the common

Com’X 200 Value

20 slaves

Same as standard value

1,000 m (3,300 ft) at 115 kBaud

20 m (66 ft) for 1 tap-off

40 m (131 ft) divided by the number of tap-offs on the multiple junction box

510

Ω pull-up resistor at the 5 V

510 Ω pull-down resistor at the common

NOTE: These polarization resistors are integrated in the Com’X 200

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Wiring of the Modbus Communication Network

Characteristics

Line terminator

Common polarity

Standard Value

Line terminator at both ends of the bus

(R or RC)

Com’X 200 Value

A 120

Ω resistor +/- 5% at both ends of the bus

The common polarity is connected to the protective ground in at least 1 point on the bus.

Same as standard value

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Wiring of the Modbus Communication Network

Modbus Communication Port Wiring Terminal Characteristics

General

The main physical characteristics of a Modbus port are:

Physical interface

Connector

Polarization

Multipoint 2-wire RS 485 - electrical networking

Terminal block and RJ45

Integrated

Physical Interface and Connectors

Refer to the Com’X 200 physical description for connectors layout. (

see page 50 )

RJ45 Connector Pinout

The Com’X 200 is connected to the Modbus network with a shielded RJ45 connector in compliance with the following wiring:

Front view

The RJ45 wiring layout is:

Pin no.

1

2

3

6

7

4

5

8

Signal

D1+

D0-

0VL

Description

Not connected

Not connected

Not connected

Transceiver terminal 1

Transceiver terminal 0

Not connected

Not connected

Signal and power supply common

Open-Style Connector

Connect the Com’X 200 to the Modbus network with an open style connector in compliance with the following plug-in terminals and pin assignments.

Plug-in terminals

Pin assignments

Signal

0V

D0-

D1+

Description

Signal and power supply common

Modbus shield pin

Transceiver terminal 0

Transceiver terminal 1

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Wiring of the Modbus Communication Network

Wiring the Modbus Network

Overview

It is recommended to connect a Com’X 200 to a Modbus network on the RS 485 bus with the female shielded RJ45 connector.

This section describes 2 typical cases of connection of the Com’X 200 to the bus:

With an open-style connector.

With an RJ45 connector.

Modbus Wiring Rules

Apply all general wiring rules (

see page 24

).

NOTICE

COMMUNICATION MALFUNCTION

Place a line terminator at each end of the bus to avoid malfunctions on the communication bus.

Respect all the wiring and grounding rules in order to avoid communication malfunctions due to EMC disturbance.

Failure to follow these instructions can result in equipment damage.

NOTE: A line terminator is integrated in the Com’X 200 and can be activated through the web interface if the Com’X 200 is located at 1 end of the Modbus line.

For more information, refer to the Electrical Installation Guide (available in English only), chapter

ElectroMagnetic Compatibility (EMC).

Open-Style Connector Wiring Rules

NOTE: Add a heat-shrink sleeve at the end of the stripped cable shield to regroup metallic strands.

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Connection of the Com’X 200 via its RJ45 Connector

The wiring diagram for connecting the Com’X 200 installed in an enclosure to the RS 485 bus via the RJ45 connector is as follows:

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1 Master (PLC, PC, or communication module) with line terminator

2 Modbus shielded cable with 2 RJ45 connectors

3 Grounding of the Modbus cable shield

4 Modbus T-junction boxes VW3 A8 306 TF•• (with cable)

5 Grounding of the Modbus T-junction boxes

6 Line terminator for RJ45 plug VW3 A8 306 R (120

Ω)

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Wiring of the Modbus Communication Network

Connection of the Com’X 200 via the Open-Style Connector

The wiring diagram for connecting the Com’X 200 installed in an enclosure to the RS 485 bus via the open style connector is as follows:

Inverting pin A, –, Tx–, Rx–, D0

Non-inverting pin B, +, Tx+, Rx+, D1

Reference pin SC, G

Shield sh, shld

List of Modbus Accessories

Designation

T-junction boxes

Line terminator for RJ45 connector

Line terminator for open-style connector

Description

Box with 2 RJ45 female connector for trunk cable and an integrated 0.3 m

(1 ft) cable with 1 RJ45 male connector for tap-off

Box with 2 RJ45 female connector for trunk cable and an integrated 1 m

(3.2 ft) cable with 1 RJ45 male connector for tap-off

R = 120

Ω

R = 120

Ω

Reference Number

VW3 A8 306 TF03

VW3 A8 306 TF10

VW3 A8 306 R

VW3 A8 306 DR

List of Modbus Cables

Designation

Shielded cable for Modbus bus, with 2 RJ45 connectors

Shielded cable for Modbus bus, with 1 RJ45 connectors and 1 stripped end

Shielded cable for Modbus bus, with 2 stripped ends

Belden cable or equivalent

Length

0.3 m (1 ft)

1 m (3.2 ft)

3 m (9.8 ft)

3 m (9.8 ft)

100 m (320 ft)

200 m (640 ft)

500 m (1,600 ft)

305 m (1,000 ft)

305 m (1,000 ft)

305 m (1,000 ft)

Reference Number

VW3 A8 306 R03

VW3 A8 306 R10

VW3 A8 306 R30

VW3 A8 306 D30

TSX CSA 100

TSX CSA 200

TSX CSA 500

3107A

7201A

9842

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