Honeywell UDA2182 User manual

Honeywell Process Solutions
UDA2182
Communications
User Guide
70-82-25-126
January 2009

ii UDA2182 Communications User Guide January 09
Copyright, Notices, and Trademarks
Printed in U.S.A. – © Copyright 2008 by Honeywell
Revised – January 2009
Warranty/Remedy
Honeywell warrants goods of its manufacture as being free of defective materials and faulty
workmanship. Contact your local sales office for warranty information. If warranted goods are
returned to Honeywell during the period of coverage, Honeywell will repair or replace without charge
those items it finds defective. The foregoing is Buyer's sole remedy and is in lieu of all other
warranties, expressed or implied, including those of merchantability and fitness for a
particular purpose. Specifications may change without notice. The information we supply is
believed to be accurate and reliable as of this printing. However, we assume no responsibility for its
use.
While we provide application assistance personally, through our literature and the Honeywell web
site, it is up to the customer to determine the suitability of the product in the application.
Honeywell Process Solutions
2500 W. Union Hill Drive
Phoenix, Arizona 85027
Modbus is a registered trademark of MODICON, Inc.
Windows is an addressed trademark of Microsoft Inc.
The omission of a name from this list is not to be interpreted that the name is not a trademark.
Reference: Modicon Modbus Protocol Reference Guide - PI-MBUS-300 Rev. G

January 09 UDA2182 Communications User Guide iii
About This Document
Abstract
This document provides information specific to the communications interface for Honeywell’s Universal Dual
Analyzer (UDA) 2182.
In this document you will find:
•How to wire the Ethernet and serial ports
•How to configure the Ethernet port settings
•How to use Modbus RTU to read and write UDA parameters on the serial port
•How to use Modbus TCP to read and write UDA parameters on the Ethernet port
•How to use the UDA web pages
•How to send email alarm events from the UDA
Contacts
World Wide Web
The following lists Honeywell’s World Wide Web sites that will be of interest to our customers.
Honeywell Organization WWW Address (URL)
Corporate http://www.honeywell.com
Honeywell Field Solutions http://www.honeywell.com/ps
Technical tips http://content.honeywell.com/ipc/faq
Telephone
Contact us by telephone at the numbers listed below.
Country Organization Phone Number
United States and Canada Honeywell
1-800-423-9883 Tech. Support 1-800-525-7439 Service
Acronyms and Definitions
UDA Universal Dual Analyzer
TCP Transmission Control Protocol
IP Internet Protocol
IE Internet Explorer
SMTP Simple Mail Transfer Protocol
DNS Domain Name System
DHCP Dynamic Host Configuration Protocol
TFTP Trivial File Transfer Protocol

iv UDA2182 Communications User Guide January 09
Contents
1. INTRODUCTION................................................................................................... 1
1.1 Overview........................................................................................................................................1
1.2 Specifications .................................................................................................................................2
2. COMMUNICATION CARD WIRING...................................................................... 3
2.1 Overview........................................................................................................................................3
2.2 Ethernet Port Wiring ......................................................................................................................3
2.3 Serial Port Wiring........................................................................................................................... 4
3. UDA COMMUNICATIONS SETUP ....................................................................... 5
3.1 UDA Ethernet Communications Setup...........................................................................................5
3.1.1 Overview .............................................................................................................................5
3.1.2 Setting up a Static IP Address using the Front Panel ..........................................................6
3.1.3 Setting up DHCP using the front-panel...............................................................................8
3.2 UDA Serial Communications Setup...............................................................................................9
4. MODBUS RTU SERIAL COMMUNICATION PORT........................................... 10
4.1 Overview......................................................................................................................................10
4.2 Modbus RTU Message Format ....................................................................................................10
4.3 Modbus RTU Link Layer.............................................................................................................11
4.4 General Modbus RTU message format ........................................................................................ 11
4.5 Modbus RTU Data Layer.............................................................................................................11
5. MODBUS/TCP INTERFACE............................................................................... 12
5.1 Introduction..................................................................................................................................12
5.2 Modbus/TCP Protocol..................................................................................................................12
5.3 Parameter Addressing...................................................................................................................12
6. IEEE 32-BIT FLOATING POINT REGISTER INFORMATION............................ 13
6.1 IEEE Floating Point Data Format.................................................................................................13
7. MODBUS DOUBLE REGISTER FORMAT......................................................... 16
7.1 Overview......................................................................................................................................16
7.2 IEEE Floating Point Formats........................................................................................................17
7.3 Unsigned/signed 32-bit Register Formats ....................................................................................18
7.4 Setting Up the Modbus Double Register Format ......................................................................... 19

January 09 UDA2182 Communications User Guide v
8. MODBUS/TCP & MODBUS RTU FUNCTION CODES....................................... 21
8.1 Function code definitions.............................................................................................................21
8.2 Function Code 03- Read Holding (Data) Registers......................................................................22
8.3 Function Code 04 - Read Input Registers.....................................................................................23
8.4 Function Code 16 (10h) - Preset Multiple Registers....................................................................24
8.5 Function Code 17 (11h) - Report UDA ID................................................................................... 25
9. MODBUS RTU EXCEPTION CODES................................................................. 27
9.1 Introduction..................................................................................................................................27
10. PARAMETERS ACCESSIBLE WITH FUNCTION CODES 03 AND 10H........... 29
10.1 Variables...................................................................................................................................29
10.2 Holding Registers Map.............................................................................................................29
11. PARAMETERS ACCESSIBLE WITH FUNCTION CODE 04.............................. 31
11.1 Signals.......................................................................................................................................31
11.2 Input Registers Map..................................................................................................................31
12. WEB PAGES....................................................................................................... 38
12.1 Overview...................................................................................................................................38
12.2 Login Page................................................................................................................................38
12.3 Welcome Page ..........................................................................................................................40
12.4 Network Configuration Page ....................................................................................................41
12.4.1 IP Address Configuration Page......................................................................................42
12.4.2 SMPT Server Name Configuration Page.......................................................................43
12.4.3 Add Alarm Recipient Configuration Page.....................................................................44
12.4.4 UDA Email Address Configuration Page......................................................................45
12.5 Parameters Page........................................................................................................................46
12.6 Optional Parameters Page.........................................................................................................47
12.7 Event History Web Page...........................................................................................................48
12.8 About Web Page.......................................................................................................................49
12.9 Contact Web Page.....................................................................................................................50
12.10 Website Page.........................................................................................................................51
12.11 Log Off Page.........................................................................................................................52
INDEX...........................................................................................................................53

vi UDA2182 Communications User Guide January 09
Tables
Table 3-1 Configurable Parameters ______________________________________________________ 5
Table 3-2 Setting Up a Static Address ____________________________________________________ 6
Table 3-3 Setting Up DHCP using the Front Panel __________________________________________ 8
Table 4-1 Modbus RTU Message Formats _______________________________________________ 10
Table 7-1 Modbus Double Register Format Selections ______________________________________ 16
Table 7-2 IEEE Floating Point Number Examples in Big Endian Format _______________________ 18
Table 8-1 Modbus/TCP and Modbus RTU Function Codes Definitions_________________________ 21
Table 9-1 Modbus RTU Data Layer Status Exception Codes _________________________________ 28
Table 10-1 Holding Registers Map _____________________________________________________ 29
Table 11-1 Holding Registers Map _____________________________________________________ 31
Table 12-1 Setting a Static IP Address __________________________________________________ 42
Table 12-2 Setting a SMPT Server Name ________________________________________________ 43
Table 12-3 Adding an Alarm Recipient__________________________________________________ 44
Table 12-4 UDA Email Address Configuration____________________________________________ 45

January 09 UDA2182 Communications User Guide vii
Figures
Figure 2-1 Communication Card Location_________________________________________________ 3
Figure 2-2 Ethernet Port Wiring _________________________________________________________ 3
Figure 2-3 Serial Port Wiring ___________________________________________________________ 4
Figure 5-1 Modbus RTU Protocol within a TCP/IP Frame___________________________________ 12
Figure 6-1 IEEE Floating Point Data format______________________________________________ 13
Figure 7-1 IEEE Floating Point Formats_________________________________________________ 17
Figure 12-1 Login Page ______________________________________________________________ 38
Figure 12-2 Welcome Page ___________________________________________________________ 40
Figure 12-3 Network Configuration Page ________________________________________________ 41
Figure 12-4 IP Address Configuration___________________________________________________ 42
Figure 12-5 SMTP Server Name _______________________________________________________ 43
Figure 12-6 Add Alarm Recipient ______________________________________________________ 44
Figure 12-7 UDA Email Address Configuration___________________________________________ 45
Figure 12-8 Monitor Parameters Page___________________________________________________ 46
Figure 12-9 Monitor Optional Parameters Page ___________________________________________ 47
Figure 12-10 Event History Page_______________________________________________________ 48
Figure 12-11 About Page_____________________________________________________________ 49
Figure 12-12 Contact Page____________________________________________________________ 50
Figure 12-13 Honeywell Website Page __________________________________________________ 51
Figure 12-14 Log Off Page ___________________________________________________________ 52

Introduction
January 09 UDA2182 Communications User Guide 1
1. Introduction
1.1 Overview
The UDA2182 provides Modbus communications support on two communication interfaces using the
optional Communication Card.
Serial port provides
•RS422/RS485 multi-drop
•2400 to 115200 programmable baud rate
•Modbus RTU protocol to read signals including PV, Temperature, Alarm Status, outputs, relay
status, etc.
•Read/write four analog and four digital variables (Note 1)
•Can communicate to the P.IE. tool
Ethernet port provides:
•Up to 5 Modbus TCP connections simultaneously
•Ethernet parameters are configured via the front-panel or web pages.
•Web server with up to 10 clients simultaneously
•Web pages (Note 2) setup the Ethernet port settings and monitor readings, alarms, statuses,
events. See Section 12
•Multi-language email to send alarm status changes. Alarm notification to eight email addresses.
These must be configured using web pages signed in as the administrator.
•DHCP: ( Dynamic Host Configuration Protocol) selectable via web page or front-panel
•Firmware upgrade to Main CPU board
•Firmware upgrade to Communications card
•Can communicate to the P.IE. tool
Note 1
There are four analog and four digital variables. These variables can be read and written remotely using
Modbus function codes.
Variables will appear as a selection for various parameters:
•Analog variables can be an alarm source, analog relay source, current output source, monitor
source, math source, auxiliary switch source, PID TRV, and PID remote setpoint.
•Digital variables can be an alarm disable, remote setpoint select, Tune Set2 select, digital relay
source, logic-in source, auxiliary switch select, PID TRC select, PID RSP select, and auto cycle
start source.
Note 2
Web pages (Section 12) provide the following:
•Multiple language support
•“Guest” accessibility for read-only permission
•“Admin” accessibility for read and write permission
•Readings of Inputs, Outputs, and Relay Outputs
•Status of Inputs, Outputs, and Alarms.
•Readings and Status of optional parameters (control, pharma, and auto-cycle)
•List of last twelve events
•Network configuration including IP address, subnet mask, gateway etc.
•Email configuration for alarm event notification

Introduction
2 UDA2182 Communications User Guide January 09
1.2 Specifications
RS422/RS485 Modbus
RTU Slave
Communications Interface
(Optional)
Baud Rate: 2400, 4800, 9600, 19200, 38400, 57600, or 115200 selectable
Data Format:: IEEE floating point and 32-bit integer. Word swap configurable.
Length of Link:
2000 ft (600 m) max. with Belden 9271 Twinax Cable and 120 ohm termination resistors
4000 ft (1200 m) max. with Belden 8227 Twinax Cable and 100 ohm termination resistors
Link Characteristics: Two-wire (half-duplex), multi-drop Modbus RTU protocol, 15 drops maximum or
up to 31 drops for shorter link length.
Modbus RTU slave: Provides monitoring of inputs outputs, statuses, alarms, and variables. Provides
writing of variables for remotely modifying parameter settings.
Ethernet TCP/IP
Communications Interface
(Optional)
Type: 10 or 100 BaseT; auto-speed and auto-polarity sensing
Length of Link: 330 ft. (100 m) maximum. Use Shielded twisted-pair, Category 5 (STP CAT5) Ethernet
cable.
Link Characteristics: Four-wire plus shield, single drop, five hops maximum
IP Address: IP Address is 192.168.1.254 as shipped from the factory
Recommended network configuration: Use Switch rather than Hub in order to maximize UDA Ethernet
performance
Configuration: Ethernet parameters are configured via the front-panel or web pages.
Modbus TCP/IP: Five simultaneous socket connections provide monitoring of inputs outputs, statuses,
alarms, and variables. Provides writing of variables for remotely modifying parameter settings.
Modbus TCP/IP Data Format: IEEE floating point and 32-bit integer. Word swap configurable.
Web server: multiple client support
Web pages: monitoring inputs, outputs, statuses, alarms, and events
Multi-language Email: Alarm notification to eight email addresses. These must be configured using
web pages signed in as the administrator.
DHCP: ( Dynamic Host Configuration Protocol) selectable via web page or front-panel

Communication Card Wiring
January 09 UDA2182 Communications User Guide 3
2. Communication Card Wiring
2.1 Overview
The Communications Card provides one Serial Port and one Ethernet Port. It is installed in the slot next to
the Power Supply Board.
Power Supply Board Communications Card
Ethernet Port
RS485 Port
Power Supply Board Communications Card
Ethernet Port
RS485 Port
Figure 2-1 Communication Card Location
2.2 Ethernet Port Wiring
Ethernet RJ45 ConnectorEthernet RJ45 Connector
Figure 2-2 Ethernet Port Wiring
•Connect terminal 1 of the Communications Card to the chassis ground bar
•Connect an Ethernet cable to the Ethernet card’s RJ45 connector. Cable polarity can be
either Straight-thru or Cross over.

Communication Card Wiring
4 UDA2182 Communications User Guide January 09
2.3 Serial Port Wiring
Figure 2-3 Serial Port Wiring
•Terminal 1 must be connected to chassis ground even if only Ethernet communications will be
used. The jumper is not installed by the factory.
•Terminal 2 is a floating terminal that can be used to daisy-chain the shield.
•Terminal 3 is the negative communication signal
•Terminal 4 is the positive communication signal
•If the UDA is at the end of the link, connect a terminating resistor across TX+ and TX-. Use a 120
ohm resistor for Belden 9271 Twinax Cable. Use a 100 ohm resistor for Belden 8227 Twinax
Cable.
•The shield must be grounded at one end. Normally, this is done at the host’s connector. If this is not
possible, and the UDA is at the end of the link, connect a jumper between terminal 1 (chassis
ground) and terminal 2 (shield).

UDA Communications Setup
January 09 UDA2182 Communications User Guide 5
3. UDA Communications Setup
3.1 UDA Ethernet Communications Setup
3.1.1 Overview
The UDA provides the capability to use either a static IP address or a dynamically allocated IP address. A
dynamically allocated IP address requires a DHCP host to be present on the network which provides the
UDA with an IP address when it first connects to the link. In most cases, a static IP address will be used for
Modbus TCP because the client needs to know the actual IP of the UDA in order to communicate to it. If
DHCP is desired, the DHCP IP address should be permanently assigned to the MAC address of the UDA
communication card. The MAC address is visible from the front panel in the Communications Status Menu
and the “about” web page.
The Ethernet parameters can be set up using the UDA front-panel or the web pages. The PIE tool cannot be
used to setup the Ethernet parameters.
Table 3-1 Configurable Parameters
Parameter Description Default value
IP Address This is the address of the device on the Ethernet link. It is
made up of four bytes called octets and is identified in decimal
notation where each number represents a value from 0 to
255. If DHCP is used, this address gets automatically
assigned by the DHCP server.
192.168.1.254
Subnet Mask The subnet mask defines the size of the subnet. 255.255.255.0
Default
Gateway The IP address of the device (router or switch) that provides access to another network. If the Modbus TCP client and the
UDA are on the same subnet, this address is not needed. It is
needed if e-mail and web pages are used. If DHCP is used,
this address gets automatically assigned by the DHCP server.
1.0.0.0
DNS Server The IP address of the network’s domain name server. This
address is needed when a domain name is used for the email
server. It is not used for Modbus TCP or web pages. If DHCP
is used, this address gets automatically assigned by the
DHCP server.
1.0.0.0

UDA Communications Setup
6 UDA2182 Communications User Guide January 09
3.1.2 Setting up a Static IP Address using the Front Panel
Be sure you have an IP address that allows it to be accessible on the intended Ethernet network. Consult
your IT department or network administrator for allocating IP addresses to the UDAs as required.
You will need to set each UDA’s IP address prior to network connection since every UDA is shipped with
the default IP address of 192.168.1.254. Placing multiple UDAs on the same network before they have
been given unique IP addresses will cause problems.
Table 3-2 Setting Up a Static Address
Step Action
1 On the front panel, select the Communication menu option in the Setup menu.
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
2 In the Communication menu, select Ethernet.
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
You will see the following Parameters:
Port Reset
DHCP (Dynamic Host Configuration Protocol)
IP Addr Octet 1-4 (IP Address)
SbntMsk Octet 1-4 (Subnet Mask)
Dflt Gtwy Octet 1-4 (Default Gateway)
DNS Srvr Octet 1-4 (Domain Name Service)
3 Set DHCP to No.
4 Set the IP Addr octets 1 through 4 to the IP address where octet 1 is the left-most IP
address octet and octet 4 is the right-most IP address octet. For example, for the default
address of 192.168.1.254, octet 1 equals 192, octet 2 equals 168, octet 3 equals 1, and
octet 4 equals 254.
5 Set the subnet mask octets 1 through 4.
6 Set the Default gateway octets 1 through 4.
7 If you are not using a DNS server to identify your email server’s address, you can leave the

UDA Communications Setup
January 09 UDA2182 Communications User Guide 7
Step Action
DNS server octets equal to their defaults. You don’t need the DNS server for Modbus TCP
or web pages.
8 Scroll to Port Reset at the top of the menu, and press enter.
Change the value to Enable and press enter to lock the values into the communication card.
To verify the UDA IP address, connect the UDA to your network or directly to a PC, and ping the IP
address. When connecting directly to the PC, you need to make sure the PC Network card is configured to
be on the same subnet.
Note: The fixed IP address of each UDA shall be set independently prior to placing on the network. See
your IT systems administrator for allocating IP addresses, subnet masks, or default gateway IP address as
necessary (network address filtering and routing may be necessary if the UDA network access will not to
be confined locally within the plant environment).

UDA Communications Setup
8 UDA2182 Communications User Guide January 09
3.1.3 Setting up DHCP using the front-panel
It is recommended that the IP addresses assigned to the UDA by the DHCP server are fixed, so that the
Modbus host can locate the UDA on the network. Consult your IT department or network administrator for
allocating DHCP IP addresses to specific devices.
Table 3-3 Setting Up DHCP using the Front Panel
Step Action
1 On the front panel, select the Communication menu option in the Setup menu.
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
2 In the Communication menu, select Ethernet.
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
You will see the following Parameters:
Port Reset
DHCP (Dynamic Host Configuration Protocol)
IP Addr Octet 1-4 (IP Address)
SbntMsk Octet 1-4 (Subnet Mask)
Dflt Gtwy Octet 1-4 (Default Gateway)
DNS Srvr Octet 1-4 (Domain Name Service)
3 Set DHCP to Yes.
4 Scroll to Port Reset at the top of the menu, and press enter.
Change the value to Enable and press enter to lock the setting into the communication card.
Once all of the UDAs are set to DHCP, power them down, connect them to the network, and then power
them up. The DHCP server should automatically assign the IP address for each UDA.
Go to the Comm Status menu in the Status Displays menu to verify that the DHCP server automatically set
the IP address.

UDA Communications Setup
January 09 UDA2182 Communications User Guide 9
3.2 UDA Serial Communications Setup
Be sure you have an IP address that allows it to be accessible on the intended Ethernet network. Consult
your IT department or network administrator for allocating IP addresses to the UDAs as required.
You will need to set each UDA’s IP address prior to network connection since every UDA is shipped with
the default IP address of 192.168.1.254. Placing multiple UDAs on the same network before they have
been given unique IP addresses will cause problems.
Table 3-4 Setting Up the serial communications
Step Action
1 On the front panel, select the Communication menu option in the Setup menu.
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
Setup
Inputs
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control*
Math
Communication
Monitors
Auxiliary
Auto Cycling*
Setup
Relays
Outputs
Maintenance
Alarms
Logic
PID Control
Math
Communication
Monitors
Auxiliary
Auto Cycling
Setup
Relays
Alarms
Logic
PID Control*
Math
Monitors
Auxiliary
Auto Cycling*
Variables
2 In the Communication menu, select RS485.
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
COMMUNICATION
RS485
Ethernet
IR FrontPanel
Modbus
You will see the following Parameters:
Port Reset
Address
Baud Rate
3 Set the Address to a unique address on your RS485 link.
Note: An address of 0 sets the UDA to its offline state.
4 Set the Baud Rate to the link’s baud rate.
Note: Other link characteristics are fixed to: no parity, 1 stop bit, and eight bit characters
5 Scroll to Port Reset at the top of the menu, and press enter.
Change the value to Enable and press enter to lock the values into the communication card.

Modbus RTU Serial Communication Port
10 UDA2182 Communications User Guide January 09
4. Modbus RTU Serial Communication Port
4.1 Overview
The Modbus RTU implementation is designed to provide a popular data exchange format connecting the UDA to
both Honeywell and foreign master devices via the optional serial communication port. Modbus RTU allows the
instrument to be a citizen on a data link shared with other devices, which subscribe to the Modicon Modbus
Protocol Reference Guide PI-MBUS-300 Rev. G specification.
The UDA does not emulate any MODICON type device. The Modbus RTU specification is respected in the
physical and data link layers. The message structure of the Modbus RTU function codes is employed and standard
IEEE 32-bit floating point and integer formats are used. Data register mapping is unique to the UDA. Sections 10
and 11 describe the parameter mapping for the UDA.
4.2 Modbus RTU Message Format
Table 4-1 Modbus RTU Message Formats
Coding system 8 bit binary
Number of data bits per
character 10 Bits
start bits – 1
data bits – 8
stop bits – 1
Parity None
Bit transfer rate 2400, 4800, 9600, 19200, 38400, 57600, 115200 Selectable
Duplex Half duplex Transceiver or TX/RX
Error checking CRC (cyclic redundancy check)
Polynomial (CRC-16 10100000000001)
Bit transfer order LSB first
End of message Idle line for 3.5 or more characters (>1.82 msec for 19200).

Modbus RTU Serial Communication Port
January 09 UDA2182 Communications User Guide 11
4.3 Modbus RTU Link Layer
The link layer includes the following properties/behaviors:
•Slave address recognition,
•Start / End of Frame detection,
•CRC-16 generation / checking,
•Transmit / receive message time-out,
•Buffer overflow detection,
•Framing error detection,
•Idle line detection.
Errors detected by the physical layer in messages received by the slave are ignored and the physical layer
automatically restarts by initiating a new receive on the next idle line detection.
4.4 General Modbus RTU message format
Query message format
[Slave Address, Function Code, Function code dependent data, CRC 16]
Response message format
[Slave Address, Function Code*, Function code dependent data, CRC 16]
* If an error is detected in a valid message the response function code is modified by adding 80 (hex) and the
function code dependent data is replaced by an exception response code as described in 9 - Modbus RTU
Exception Codes .
Between messages, the RS-485 link is in a high impedance state. During this time receiving devices are
more susceptible to noise generated false start of messages. Although noise-generated messages are
rejected due to address, framing, and CRC checking, they can cause the loss of a good message when they
are included in the message stream. In the slave the transmitting device enables its transmitter line diver
and forces an idle line state onto the link for three character time slots prior to transmitting. This forces
termination of any noise generated messages and improves message frame synchronization.
4.5 Modbus RTU Data Layer
The data layer includes:
•Diagnostic loopback,
•Function code recognition / rejection,
•Busy / repoll,
•Data error code generation
Errors detected by the data layer are rejected and the slave responds to the polling device with a Modbus-
type status exception error. A summary of the Modbus status exception codes is listed in Section 9 -
Modbus RTU Exception Codes.

Modbus/TCP Interface
12 UDA2182 Communications User Guide January 09
5. Modbus/TCP Interface
5.1 Introduction
UDA2182 supports 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 UDA’s optional 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 UDA supports 5 concurrent
host connections using Modbus/TCP protocol messaging via this port. The number of client hosts that can
access the UDA depends upon the ability of the applications to share these connections.
5.2 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.
Figure 5-1 Modbus RTU Protocol within a TCP/IP 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 UDA IP address is the identifying address, set independently at the UDA.
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 standard IEEE 32-bit floating point, 32-bit and 16-bit integer formats are used. Both big and little endian
floating point word order are supported using a Modbus Word Swap configuration parameter.
5.3 Parameter Addressing
Shown in Sections 10 and 11 are maps listing the parameter addresses.
Examples for read or write access to parameters supported by the various function codes are provided in Section 8.