ControlEdge HC900 Controller Communications User Guide

1. Introduction

1.1 Overview

Communication interfaces

The ControlEdge HC900 controller provides Modbus communication support on three communication interfaces.

 Network port: Modbus TCP on an Ethernet connection

 Serial Port S1 RS232/RS485 selectable port. (Default RS232.): Modbus RTU

 Serial Port S2 RS232/RS485 selectable port. (Default RS485.): Modbus RTU

View or print addresses

You can print out the Modbus addresses of various parameters of the configuration (signal tags, PID loops, SP programmer, etc.) using the HC Designer report functions. With HC Designer Ver. 2.1 and later, these reports may also be exported to .csv files for view/manipulation in a spreadsheet and possible import to other HMI applications.

Fixed map or custom map

The type of addressing available: fixed or custom.

1.2 Modbus/TCP Interface

Introduction

ControlEdge HC900 controllers support the Modbus/TCP (also called Modbus TCP/IP or Modbus Ethernet) protocol for communications with third party HMI and SCADA software via a direct Ethernet TCP/IP connection.

The controller’s Ethernet 10/100Base-T Host port is used for the Modbus/TCP connection. Ethernet TCP allows multiple concurrent connections to hosts for data interchange. The ControlEdge HC900 (C30/C50) supports 5 concurrent host connections using Modbus/TCP protocol messaging via this port; ControlEdge HC900 (C70/C70R) supports 10.

Interface Preparation

ATTENTION

To access the controller you must have a current Process Control Designer configuration file available. Some data is referenced relative to number, such as Signal Tags and Variables.

Other principal blocks, such as PID blocks, have offsets for parameter access dependent on the order in which the blocks were placed on the Function Block Diagram.

It is strongly recommended that you upload the controller configuration using the Process Control Designer configuration tool to assure that you have a current configuration.

The Process Control Designer tool provides a series of reports for use in Modbus Address identification. The "Tag Information" report lists the variables and Signal Tags in numeric order along with their Modbus Addresses. A "Block Modbus Address" report lists the starting addresses for all principal blocks configured, identifying the offset.

Modbus/TCP Protocol

Modbus/TCP protocol, developed by Groupe Schneider’s Modicon Division, is a popular, open standard for data interchange over Ethernet TCP/IP networks using a Modbus RTU command structure.

It is simply an encapsulation of Modicon’s Modbus RTU protocol within a TCP/IP frame as shown below, which includes header information and the Modbus frame.

The Open Modbus/TCP Specification is followed with respect to the physical, data link, and network layers. The message structure within the Modbus frame uses standard Modbus RTU function codes.

The Address part of the Modbus frame is not used (set to 00) since there is no sub-addressing intended or required. The controller IP address is the identifying address, set independently at the controller.

The error checking is supported by TCP/IP network protocols and not part of the Modbus frame.

The Transaction Identifiers and Protocol Identifiers in the header are normally all 0’s (4 bytes total) while the Length field identifies the number of bytes in the Modbus frame. The controller will transmit the correct number of bytes for the remainder of the frame. However, the controller does not check this field for messages received.

The standard IEEE 32-bit floating point and 16-bit integer formats are used.

Parameter Addressing

The definition in Table 6-1 is the fixed map overview listing starting and ending addresses.

Greater detail for parameter addressing relating to a particular function class (e.g, loops, setpoint programmer, signal tags) is in referenced sub-sections. Function Codes 1, 2, 3, 4, 5, 6, 8, 16 (10h), and 17 (11h) are supported (see Table 4-1 Modbus/TCP and Modbus RTU Function Codes Definitions).

Examples for read or write access to parameters supported by the various function codes are provided in Sections 4.3 through 4.11.

ControlEdge HC900 Ethernet Communications Setup

See the ControlEdge HC900 Control (HC) Designer Users Guide, Doc. # 51-52-25-110 or respective HC Designer Help Files for setting up the following network parameters:

IP Address, Subnet Mask (optional), Default Gateway IP Address (optional)

1. Be sure the PC, HMI panel, or other Host device has a Network Interface Card (NIC) with an IP address (fixed or DHCP served) that allows access to controllers on the same or other subnet. Consult your IT department or network administrator for allocating IP addresses to the controllers as required.

2. You will need to set each controller’s IP address prior to network connection since every ControlEdge HC900 controller is shipped with the default IP address of 192.168.1.254. Placing multiple controllers on the same network before they have been given unique IP addresses will cause problems.

3. On the PC, use the Utilities Worksheet in the HC Designer software to set up the serial RS-232 connection to the controller at the desired baud rate. This will require a null modem cable.