Figure 1-2 Ethernet 10/100Base-T Network Connections - Honeywell HC900 User Manual

Process controller

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Introduction

Modbus/TCP Interface

Ethernet 10/100Base-T Network Connections

Ethernet 10/100Base-T networks operating at 10/100MB/sec. are supported. A typical network arrangement is as

shown below.

RS232/RS485

Serial Ports S1 & S2

Ethernet Host Port E1

Ethernet Host Port E2

Setting Up the Modbus/TCP Double Register Format

The HC900 predominantly uses an IEEE floating point format for communicating data to software applications

providing Modbus/TCP protocol communications drivers. A floating point value is sent as (2) consecutive 16-bit

registers, each register of which consists of two 8-bit bytes. Some software packages require the registers and bytes

to be sent in a certain order. The controller can be configured to deliver the data in four different byte orders.

The Process Control Designer software tool allows this order to be selected as follows:

Using the Utilities Worksheet in the HC Designer software, access the Set Controller Network

Parameters button and make the selection to change the Modbus TCP Double Register Format (middle

radio button).

With the Port selected for downloading this order (using a COM port or Network port), select the

appropriate byte order format if the default (FP B) is not appropriate for the application. See Table

3-1, page 10.

3. Select Next and verify (by the response in the dialog box) that the change has been made in the

controller. This order can be changed in the RUN mode.

The Modbus TCP double register transmission format selection, FP LB "Little Endian Byte-Swapped", would be

selected for interface to most third party software packages which use this format as standard. The default, FP B

"Big Endian" is used with SpecView32 or Honeywell's PlantScape/Experion/EBI software and follows the

"Honeywell" default format of other control and recording products. It should be noted that most PC software

packages offer a register (word) swap selection in their driver package anyway, so there should never be an

incompatibility.

To other subnets

10/100Base-T

C70

Run/Pgm

Pgm

Run

Run/Pgm

I/O Port

I/O