CSZ EZT-430i Assembly instructions

Table of Contents CSZ EZT-430i REVC i
EZT-430i
Single/Dual Loop Controller
User Communications Reference Manual

EZT-430i Communications Manual
Table of Contents CSZ EZT-430i REVC i
Safety Information in this Manual
Notes, cautions and warnings appear throughout this book to draw your attention to important operational and
safety information.
A “NOTE” marks a short message to alert you to an important detail.
A “CAUTION” safety alert appears with information that is important for protecting your equipment and
performance.
A “WARNING” safety alert appears with information that is important for protecting you, others and equipment
from damage. Pay very close attention to all warnings that apply to your application.
This symbol (an exclamation point in a triangle) precedes a general CAUTION or WARNING
statement.
This symbol (a lightning bolt in a lightning bolt in a triangle) precedes an electric shock hazard
CAUTION or WARNING safety statement.
Technical Assistance
If you encounter a problem with your EZT-430i controller, review all of your configuration information to verify
that your selections are consistent with your application: inputs; outputs; alarms; limits; etc. If the problem
persists after checking the above, you can get technical assistance by dialing 1 [phone] or by faxing
your request to 1 [phone], Monday thru Friday, 7:30 a.m. to 5:30 p.m. Eastern Standard Time. You
can also email your request to [email protected].
An applications engineer will discuss your application with you.
Please have the following information available:
• Complete Model #’s and/or Serial #’s for Component(s) in Question
• Complete Software Version #’s
• All Configuration Information
• All User Manuals
Warranty and return information is on the back cover of this manual.
Your Comments
Your comments or suggestions on this manual are welcome. Please send them to:
Telephone: [phone] Fax: [phone]
[e-mail]

EZT-430i Communications Manual
Table of Contents CSZ EZT-430i REVC ii
1What is EZT-430i ?....................................................................................................1.1
1.1 Features...............................................................................................................................................1.1
2Communications Wiring...........................................................................................2.1
3Communication Basics ............................................................................................3.1
3.1 Explanation of Terms...........................................................................................................................3.1
4Serial Communication ..............................................................................................4.1
4.1 Interface Standards..............................................................................................................................4.2
4.1.1 Interface Converters......................................................................................................................4.3
4.2 Protocol................................................................................................................................................4.4
4.3 Creating your own Modbus Application ...............................................................................................4.6
4.3.1 Packet Syntax................................................................................................................................4.7
4.3.2 Error Checking.............................................................................................................................4.10
4.3.3 Transmitting and Receiving Messages .......................................................................................4.11
5EZT-430i Data Registers (standard serial interface) ............................................5.1
5.1 Control Registers .................................................................................................................................5.2
5.2 Automatic Program Registers..............................................................................................................5.7
5.2.1 Starting an Automatic Program on EZT-430i .............................................................................5.10
6EZT-430i Simulated F4S/D Interface Operation.......................................................12
6.1 F4S/D Supported Control/Monitoring Data Registers...........................................................................12
6.2 F4S/D Supported Profile Step Data Registers......................................................................................17
6.2.1 Limitations of Profile Download/Operation (IMPORTANT – Please Read!)..................................19
6.2.1.1 Sending Profiles to EZT-430i ..................................................................................................19
6.2.1.2 Setting Proper Step Times.......................................................................................................20
6.2.1.3 Setting Final Setpoints.............................................................................................................20
6.2.1.4 Starting a Profile.......................................................................................................................20

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What is EZT-430i CSZ EZT-430i REV C 1.1
1 What is EZT-430i?
The EZT-430i system combines all of the features of a loop controller, video/chart recorder and data logging
system into a single/intuitive device. Email, SMS (text messaging), FTP (file transfer protocol for automated
data backup) and remote view/control (Web server/VNC server) are standard with EZT-430i and can be
accessed via LAN/WAN using a PC, tablet or smart phone device.
Future Designs “EZT-430i” provides a 4.3”color touch screen interface with standard “Smart Device” user
interface features for single and dual loop OEM control applications. All loop configuration and runtime user
access is configurable at the device with no PC software required. OEM’s have the ability to configure
runtime features (screen availability, menus, language, etc...) to easily customize the system for their
requirements. These configurations can be imported/exported to any other EZT-430i single/dual loop device
for setup (from scratch) within minutes.
Individual high performance board level PID loop control boards (one for each loop) offer up to four control
outputs each, powerful profiling capabilities with up to three events and full auto tune functionality with high
resolution process inputs.
1.1 Features
Each of the EZT-430i loop control boards provide a single digital input that can be programmed as a
automatic program control input for run, hold or abort, a manual mode or failure transfer control input or a
program advance to next segment control input.
Each of the loop control boards also provide up to four control outputs which can be used as PID control
outputs for heat/cool, direct outputs for controlling external equipment related to the application through
software switches called events, or be programmed to act as system alarm outputs.
EZT-430i can be operated in single set point or automatic program control mode. Program entry is made
easy through the use of copy, paste and delete menu selections. Programs can be copied to the external
USB memory stick and then imported to another EZT-430i controller which eliminates the need to enter
duplicate programs into multiple systems.
Data file analysis tools make looking at historical data a simple task. Any control variable saved to the data
file can be plotted on the historical data chart for any time frame within the data file’s total time range.
The built in Ethernet functionality includes a ‘Web Server’ to provides access to all EZT-430i data (view only),
a VNC interface for remote control and monitoring and an NTS clock, all available via a local Intranet
connection (wired or wireless), or the World Wide Web using standard software like Microsoft’s Internet
Explorer.
EZT-430i provides a rich set of tools for control interaction and process monitoring. Views include single and
dual loop views, charts, alarm, automated program status as well as historical data, alarm log and audit trail
views. The menu driven interface eliminates screen “clutter” by providing an easy to use “Smart Device”
interface for interaction between the user and EZT-430i.
EZT-430i can store more than one year of data on its SD memory card. Data logging can be enabled
manually or automatically during program operation. Data backup is provided with a USB memory stick for
plug and play transfer of files to any PC running Microsoft Windows XP operating systems and via the FTP
back-up utility.
EZT-430i protects system access with 4 level security (user rights based), audit trails that document all user
activity and ensures data integrity by digitally signing all data files and audit trails to meet regulatory
requirements.

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What is EZT-430i CSZ EZT-430i REV C 1.2
The EZT-430i controller includes the following features:
• Single/Dual loop controller models (automatic program operation included).
• Touch screen, “Smart Device” user interface (UI).
• Video recorder mode for view only applications.
• Email, SMS, FTP, VNC and Web functionality standard.
• Remote View/Control using PC, Tablet or Smartphone.
• Detailed maintenance, alarm monitoring and alarm history.
• User configurable data logging and historical data viewer.
• 4 level security with digitally signed audit trails and data files.
• National time server connectivity with daylight savings.
• Multi-lingual user interface supports over 25 languages.
• 30,000 hour LED display

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2 Communications Wiring
The EZT-430i touch screen provides an RS232C (COM1) user communications port for connecting EZT-430i
to a PC running software such as CSZ’s Envision. In order to connect EZT-430i to a PC, a cable must be
made according to the diagram below.
NOTE: DO NOT use a standard null-modem cable to connect EZT-430i to a PC. Most computers do not
provide a standard serial port and a USB to serial converter must be used. Incompatibilities may
exist between EZT-430i and certain USB to serial adapters which will cause EZT-430i to
malfunction when connected using a standard null-modem cable.
If more than one EZT-430i controller is to be placed on the communication link with a PC, an RS232/485
converter will be required for each EZT-430i and the PC in order to convert the RS232 communications port
to RS485 multi-drop communications network for connecting multiple EZT-430i controllers on the PC
communications link.
WARNING:
To avoid potential electric shock and other hazards, all mounting and
wiring for EZT-430i must conform to the National Electric Code (NEC)
and other locally applicable codes.
Special expertise is required to install, wire, configure and operate the
EZT-430i controller. Personnel without such expertise should not
install, wire or operate nCompass.
CAUTION:
Prevent metal fragments and pieces of wire from dropping inside the
housing of any EZT-430i component. If necessary, place a cover
over the component during installation and wiring. Ingress of such
fragments and chips may cause a fire hazard, damage or malfunction
of the device.
Locate the EZT-430i touch screen and all related control components
away from AC power/motor wiring and sources of direct heat output
such as transformers, heaters or large capacity resistors.

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Communications Wiring CSZ EZT-430i REV C 2.2
NOTE: The connection requires a single twisted-pair cable that is daisy-chained from one EZT-430i to the
next. When using shielded twisted-pair cable, be sure to ground only when end of the cable,
preferably at the RS232 to RS485 network adapter. Allowing any other portion of the cable shield to
come in contact with ground, or grounding both ends, will cause ground loop currents to flow in that
section of the cable which can cause communication errors.

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Communication Basics CSZ EZT-430i REV C 3.1
3 Communication Basics
The purpose of this document is to provide users interested in using data communications with the EZT-430i,
the ability to set up and use a simple network of one or more EZT-430i controllers by providing a basic
understanding of data communications using standard definitions, interfaces and protocols.
In this manual, numbers in the format ‘0x00’ represent values in hexadecimal. Numbers in the format ‘0’
represent values in decimal and finally, numbers in the format ‘00000000’ represent values in binary unless
otherwise stated.
3.1 Explanation of Terms
Machine-to-Machine Communication
In order for machines to communicate with each other, they need a code called a character format or
character set. They require rules called protocol to govern their conversation and prevent confusion and
errors. Computers need a connecting interface over which to communicate. They may use one pair of wires
to send information in one direction and another pair to send in the opposite direction (full duplex), or they
may use one pair to send data in both directions (half duplex).
Character Format
The code or character format for EZT-430i data communications is shared by virtually everyone in the
electronics industry. This code defines a stream of 1’s and 0’s that are created by varying a voltage signal in
a regular manner. This code is the American Standard Code for Information Interchange, called ASCII.
Bits and Bytes
The word “bit” is simply the contraction of the words binary digit. A bit is the basic unit in ASCII. It is either a
“1” or a “0”. A byte is a string of eight bits that a computer treats as a single character. ASCII can use a
single byte to represent each letter of the alphabet, each digit and each punctuation mark we use.
ASCII
The ASCII code defines 128 separate characters, one for each letter, digit and punctuation mark. ASCII also
includes control characters similar to those we find on computer keys, such as backspace, shift and return. It
also has nine communications control characters for identification, enquiry (inquiry), start of text, end of text,
end of transmission, acknowledge, negative acknowledge and escape. The ASCII code is sometimes written
in a base 16 number system that is called hexadecimal or “hex” for short. The numbers 0 through 9
represents the first ten digits of this system, and the letters A through F represents the final six digits. The
128 ASCII character codes with the decimal, binary and hexadecimal equivalents are listed in the following
table.
ASCII Control Codes
ASCII Control Codes are used to give instructions to the remote device and result in specific actions, such as
a line feed instruction on a printer. ASCII Control Codes, the first 33 ASCII characters (non printable), are
important for the operation of communicating equipment. They give instruction to remote devices that result
in specific actions such as a line feed on a printer. Holding down the keyboard control key while pressing the
appropriate keyboard key is what sends these values.

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ASCII Character Chart
Char Code Decimal Binary Hex Char Code Decimal Binary Hex
NUL Ctrl @ 0 00000000 00 @ Shift 2 64 01000000 40
SOH Ctrl A 1 00000001 01 A Shift A 65 01000001 41
STX Ctrl B 2 00000010 02 B Shift B 66 01000010 42
ETX Ctrl C 3 00000011 03 C Shift C 67 01000011 43
EOT Ctrl D 4 00000100 04 D Shift D 68 01000100 44
ENQ Ctrl E 5 00000101 05 E Shift E 69 01000101 45
ACK Ctrl F 6 00000110 06 F Shift F 70 01000110 46
BEL Ctrl G 7 00000111 07 G Shift G 71 01000111 47
BS Ctrl H 8 00001000 08 H Shift H 72 01001000 48
TAB Ctrl I 9 00001001 09 I Shift I 73 01001001 49
LF Ctrl J 10 00001010 0A J Shift J 74 01001010 4A
VT Ctrl K 11 00001011 0B K Shift K 75 01001011 4B
FF Ctrl L 12 00001100 0C L Shift L 76 01001100 4C
CR Ctrl M 13 00001101 0D M Shift M 77 01001101 4D
SO Ctrl N 14 00001110 0E N Shift N 78 01001110 4E
SI Ctrl O 15 00001111 0F O Shift O 79 01001111 4F
DLE Ctrl P 16 00010000 10 P Shift P 80 01010000 50
DC1 Ctrl Q 17 00010001 11 Q Shift Q 81 01010001 51
DC2 Ctrl R 18 00010010 12 R Shift R 82 01010010 52
DC3 Ctrl S 19 00010011 13 S Shift S 83 01010011 53
DC4 Ctrl T 20 00010100 14 T Shift T 84 01010100 54
NAK Ctrl U 21 00010101 15 U Shift U 85 01010101 55
SYN Ctrl V 22 00010110 16 V Shift V 86 01010110 56
ETB Ctrl W 23 00010111 17 W Shift W 87 01010111 57
CAN Ctrl X 24 00011000 18 X Shift X 88 01011000 58
EM Ctrl Y 25 00011001 19 Y Shift Y 89 01011001 59
SUB Ctrl Z 26 00011010 1A Z Shift Z 90 01011010 5A
ESC Ctrl [ 27 00011011 1B [ [ 91 01011011 5B
FS Ctrl \ 28 00011100 1C \ \ 92 01011100 5C
GS Ctrl ] 29 00011101 1D ] ] 93 01011101 5D
RS Ctrl ^ 30 00011110 1E ^ Shift 6 94 01011110 5E
US Ctrl _ 31 00011111 1F _ Shift - 95 01011111 5F
SP SPACE 32 00100000 20 ` ` 96 01100000 60
! Shift 1 33 00100001 21 a A 97 01100001 61
" Shift ‘ 34 00100010 22 b B 98 01100010 62
# Shift 3 35 00100011 23 c C 99 01100011 63
$ Shift 4 36 00100100 24 d D 100 01100100 64
% Shift 5 37 00100101 25 e E 101 01100101 65
& Shift 7 38 00100110 26 f F 102 01100110 66
‘ ‘ 39 00100111 27 g G 103 01100111 67
( Shift 9 40 00101000 28 h H 104 01101000 68
) Shift 0 41 00101001 29 I I 105 01101001 69
* Shift 8 42 00101010 2A j J 106 01101010 6A
+ Shift = 43 00101011 2B k K 107 01101011 6B
, , 44 00101100 2C l L 108 01101100 6C
- - 45 00101101 2D m M 109 01101101 6D
. . 46 00101110 2E n N 110 01101110 6E
/ / 47 00101111 2F o O 111 01101111 6F
0 0 48 00110000 30 p P 112 01110000 70
1 1 49 00110001 31 q Q 113 01110001 71
2 2 50 00110010 32 r R 114 01110010 72
3 3 51 00110011 33 s S 115 01110011 73
4 4 52 00110100 34 t T 116 01110100 74
5 5 53 00110101 35 u U 117 01110101 75
6 6 54 00110110 36 v V 118 01110110 76
7 7 55 00110111 37 w W 119 01110111 77
8 8 56 00111000 38 x X 120 01111000 78
9 9 57 00111001 39 y Y 121 01111001 79
: Shift ; 58 00111010 3A z Z 122 01111010 7A
; ; 59 00111011 3B { Shift [ 123 01111011 7B
< Shift , 60 00111100 3C | Shift \ 124 01111100 7C
= = 61 00111101 3D } Shift ] 125 01111101 7D
> Shift. 62 00111110 3E ~ Shift ` 126 01111110 7E
? Shift / 63 00111111 3F DEL Delete 127 01111111 7F

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4 Serial Communication
The user communications interface for EZT-430i employs serial communication, which is the exchange of
data in a one-bit-at-a-time, sequential manner on a single data line or channel. Serial contrasts with parallel
communication, which sends several bits of information simultaneously over multiple lines or channels. Not
only is serial data communication simpler than parallel, it is also less costly.
Baud Rate
The baud unit is named after Jean Maurice Emile Baudot, who was an officer in the French Telegraph
Service. He is credited with devising the first uniform-length 5-bit code for characters of the alphabet in the
late 19th century. What baud really refers to is modulation rate or the number of times per second that a line
changes state. This is not always the same as bits per second (BPS). However, if you connect two serial
devices together using direct cables then baud and BPS are in fact the same. Thus, if you are running at
9600 BPS, then the line is also changing states 9600 times per second.
Typical baud rates used for computers are 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600
and 115200 baud. As the baud rate increases, so does the transmission rate of data. Thus you get more
information in a shorter period of time. However, the faster the transmission rate, the more susceptible it is to
error due to the quality of the cable and sources of electrical “noise” in the environment. When operating in
the standard interface mode, EZT-430i uses a 9600 baud rate. When operating in the simulated Watlow
F4S/D mode, EZT-430i uses a 19200 baud rate. In order for a device to communicate with EZT-430i , it must
have its serial port set for either 9600 baud or 19200 baud based on the selected interface type in order for
data communications to work properly.
Start and Stop Bits
The start bit informs the receiving device that a character is coming, and a stop bit tells it that a character is
complete. The start bit is always a 0. The stop bit is always a 1. The human speech equivalent of these bits
could be a clearing of the throat to get someone’s attention (start bit); and a pause at the end of a phrase
(stop bit). Both help the listener understand the message.
A stop bit has a value of 1 - or a mark state - and it can be detected correctly even if the previous data bit also
had a value of 1. This is accomplished by the stop bit's duration. Stop bits can be 1, 1.5, or 2 bit periods in
length. EZT-430i uses the default – and most common – length of 1 period for the stop bit. A device used to
communicate with EZT-430i must also have its serial port set to use a stop bit of 1 in order for data
communications to work properly.
Parity Bit
Besides the synchronization provided by the use of start and stop bits, an additional bit called a parity bit may
optionally be transmitted along with the data. A parity bit affords a small amount of error checking, to help
detect data corruption that might occur during transmission. There are several defined parity selections
available for serial communications. They are even parity, odd parity, mark parity, space parity or none at all
can be used.
When even or odd parity is being used, the number of marks (logical 1 bits) in each data byte are counted,
and a single bit is transmitted following the data bits to indicate whether the number of 1 bits just sent is even
or odd. Mark parity means that the parity bit is always set to the mark signal condition and likewise space
parity always sends the parity bit in the space signal condition. Since these two parity options serve no useful
purpose whatsoever, they are almost never used.
When operating in the standard interface mode, EZT-430i offers parity settings of Even, Odd and None.
When operating in the simulated Watlow F4S/D interface mode, the parity is defaulted to “None” and is not
adjustable. In order for a device to communicate with EZT-430i , it must have its serial port set to use the
same parity setting in order for data communications to work properly.

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4.1 Interface Standards
An interface is a means for electronic systems to interact. It’s a specific kind of electrical wiring configuration.
It has nothing to do with how data is sent over that connection. The two most common interfaces used today
are RS-232, which provides a simple 1 to 1 connection and RS-485, which provides a multi-drop connection
where more than one device can be placed on the same line. The EZT-430i communications interface is RS-
232, but can be changed to RS-485 through the use of external RS232/485 adapters.
EIA-232 (Full Duplex)
An EIA-232 (formerly RS-232C) interface uses three wires: a single transmit wire; a single receive wire; and a
common line. Only two devices can use an EIA-232 interface. A -3 to -24 volt signal indicates a 1 and a +3
to +24 volt signal indicates a 0. The EIA-232 signal is referenced to the common line rather than to a
separate wire, as in EIA-485. Thus, an EIA-232 cable is limited to a maximum of 50 feet, due to noise
susceptibility.
EIA-485 (Half Duplex)
An EIA-485 interface uses two wires: a T/R+, a T/R- line. A -5-volt signal is interpreted as a 1, a +5-volt
signal as a 0. As many as 31 slave devices can be connected to a master on a multi-drop network up to 4000
feet long.
Wiring
Most PCs have a standard EIA-232 port (usually referred to as RS-232). In these instances, you must use an
interface converter to connect to an EIA-485 multi-drop system. The standards do not specify the wire size
and type. Use of 24 AWG twisted pair provides excellent results. If shielded cable is used, terminate the
shield at one end only. Always follow the manufacturer’s instructions supplied with the interface converter.
See Biasing of Buses next.
Biasing of Buses
The EIA-485 standard requires the bus to be biased for reliable communication. This requires termination
resistors to be placed across the T/R+ and T/R- wires. One resistor is placed at the PC where it connects to
the EIA-485 bus. The second resistor is placed at the last controller on the network. Do not place resistors at
each controller. The impedance of the wires used for the bus determines the resistor value. For twisted pair,
the value is typically 120 ohms. In addition, it may be necessary to have a pull-up and pull-down resistor
between the power supply and ground of the interface adapter.
Check the documentation that came with your interface adapter. Biasing the bus reduces reflection of signals
sent down the bus. These reflections are sometimes referred to as a standing wave. This condition is most
notable when communicating at high baud rates over longer distances.

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4.1.1 Interface Converters
The purpose of an interface converter is to allow two different buses to be connected together. Interface
converters are required when connecting an EIA-232 port to an EIA-485 bus. The EIA-485 bus is a half
duplex bus. This means that it can only send or receive data at any given time. Some interface converters
on the market provide the ability to have full duplex with the EIA-485 bus. This is accomplished by using two
receivers and transmitters tied in tandem. This type of converter will not work with the EZT-430i controller.
Be sure that the model you purchase is designed for half duplex.
Another consideration when selecting an interface converter is how the converter handles switching between
transmit and receive. Typically it is accomplished via a handshake line from the PC. When data flows into
the converter from the PC, a handshake line is placed high. When data flows out of the converter to the PC,
the handshake line is placed low. In this way, the handshake line controls the direction of information.
Another method of achieving this is to use a built-in timer. The converter switches to transmit when a
character is sent to it from the PC. After a period of time when the PC has not transmitted, the converter
switches to a receive mode.
It is important that you understand how your converter accomplishes this task. You are required to wire this
feature or make settings on the converter to enable this function. The PC will not talk to the controller
correctly without properly setting this. Your converter may also require settings through dip switches, to set
up communications parameters like baud rate, data bits, start bits, stop bits and handshaking. The converter
may also require a separate power supply. Some converters get their power from the handshake lines of the
PC. If you rely on this method, you will need to wire these additional lines. In addition, your software must
set these lines high. A more reliable method is to use an external power supply. This is especially necessary
when using a laptop computer. See the documentation that is provided with your converter for more
information.
Not all converters are equal in performance. If your chamber operates in a harsh, electrically noisy
environment, this can cause less robust converters to work intermittently or not at all. The following converter
has been tested and is compatible with EZT-430i . The converter is equipped with automatic send data
control circuits, driver control in the converter hardware, so you don’t have to work with software at all. The
circuit monitors data flow and enables the driver during transmission and automatically disables it when no
data is being sent. There is no need to rework software or install new drivers.
US Converters
405 W. Fairmont Dr.
Tempe, AZ 85282
E-mail: [e-mail]
www.USconverters.com
Part # XS201A RS232 to RS485 Converter
Future Design Controls
7524 West 98th Place
Bridgeview, IL 60455
Phone: [phone]
Fax: [phone]
E-mail: [e-mail]
www.futuredesigncontrols.com
Part # SNA10A Smart Network Adapter
Part # DB9M-DB9F-6ft (Cable Accessory to connect SNA10A to PC)

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4.2 Protocol
Protocol describes how to initiate an exchange. It also prevents two machines from attempting to send data
at the same time. There are a number of different data communications protocols, just as there are different
human cultural protocols that vary according to the situation.
The protocol portion of EZT-430i communications is very important, because it provides a quality of
communication that others often don’t have. Protocol-driven communications are more accurate because
they are less prone to both operator and noise errors. Protocol maintains system integrity by requiring a
response to each message. It’s like registered mail — you know that your letter has been received because
the post office sends you a signed receipt.
In EZT-430i data communications, a dialog will continue successfully as long as the messages are in the
correct form and responses are returned to the protocol leader. If the operator enters an incorrect message,
or interference comes on to the data line, there will be no response. In that case the master must retransmit
the message or go to a recovery procedure. If an operator continues to enter an incorrect message or
interference continues on the data line, the system will halt until the problem is resolved. EZT-430i uses
Modbus RTU as the protocol of choice. Modbus RTU enables a PC to read and write directly to registers
containing the EZT-430i parameters. With it, you can read all of the controller’s parameters with just a single
read command.
Modbus Remote Terminal Unit (RTU)
Gould Modicon, now called AEG Schneider, created this protocol for process control systems called
"Modbus". It has the advantage over other protocols of being extremely reliable in exchanging information.
This protocol works on the principle of packet exchanges. The packet contains the address of the controller
to receive the information, a command field that says what is to be done with the information and several
fields of data. The last item sent in the packet is a field to ensure the data is received intact. This is called a
cyclic redundancy check-sum. See the following example for information on how to generate this value. All
information is exchanged in hex numbers. EZT-430i only supports the binary version of Modbus, referenced
as RTU. The ASCII version is less efficient and is not supported. Therefore, you must be certain to format all
data in hexadecimal.
The CRC (Cyclical Redundancy Checksum) is caulated by the following steps:
1. Load a 16-bit register (called CRC register) with 0xFFFF
2. Exclusive OR the first 8-bit byte of the command message with the low order byte of the 16-bit CRC
register, putting the result in the CRC register.
3. Shift the CRC register one bit to the right with MSB zero filling. Extract and examine the LSB.
4. If the LSB of the CRC register is zero, repeat step 3, else Exclusive OR the CRC register with the
polynomial value 0xA001.
5. Repeat steps 3 and 4 until eight shifts have been performed. When this is done, a complete 8-bit byte will
have been processed.
6. Repeat steps 2 through 5 for the next 8-bit byte of the command message. Continue doing this until all
bytes of the command message have been processed. The final contents of the CRC register is the CRC
value.
When transmitting the CRC value in the message, the upper and lower bytes of the CRC value must
be swapped, i.e. the lower order byte will be transmitted first.

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Example Cyclical Redundancy Checksum (CRC) Algorithm
unsigned int ca_crc(unsigned char *start_of_packet, unsigned char *end_of_packet)
{
unsigned int crc;
unsigned char bit_count;
unsigned char *char_ptr;
/* Start at the beginning of the packet */
char_ptr = start_of_packet;
/* Initialize CRC */
crc = 0xFFFF;
/* Loop through the entire packet */
do{ /* Exclusive-OR the byte with the CRC */
crc ^= (unsigned int)*char_ptr;
/* Loop through all 8 data bits */
bit_count = 0;
do{ /* If the LSB is 1, shift the CRC and XOR the polynomial mask with the CRC */
if(crc & 0x0001){
crc >>= 1;
crc ^= 0xA001;
}
/* If the LSB is 0, shift the CRC only */
else{
crc >>= 1;
}
} while(bit_count++ < 7);
} while(char_ptr++ < end_of_packet);
return(crc);
}

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4.3 Creating your own Modbus Application
Listed below are a few of the more common software packages that claim to support the Modbus protocol.
This list is provided as informational only. Contact the software manufacturer for more information on
applying their software.
LabView by National Instruments Wonderware by Wonderware SpecView by SpecView Corporation
11500 N Mopac Expwy 26561 Rancho Pkwy. South 13409 53rd Ave NW
Austin, TX 78759-3504 Lake Forest, CA 92630 Gig Harbor, WA 98332
Phone [phone] Phone [phone] Phone [phone]
http://www.natinst.com http://www.wonderware.com http://www.specview.com
If you already have a software application that uses Modbus, you can simply skip to the EZT-430i parameter
table in the Getting Started section for the information your program requires. The rest of this section
provides information on writing a software application that uses Modbus.
1. You must code messages in eight-bit bytes, with even parity, one stop bit (8, even, 1). EZT-430i has its
parity set to even as default from the factory.
2. Negative parameter values must be written in twos' complement format. Parameters are stored in two-
byte registers accessed with read and write commands to a relative address.
3. Messages are sent in packets that must be delimited by a pause at least as long as the time it takes to
send 28 bits (3.5 characters). To determine this time in seconds, divide 28 by the baud rate. In the case
of EZT-430i communications at 9600 baud, this caulates to a minimum period of ~3ms.
In addition, the EZT-430i timeout period must be added to that in order to properly time the send and
receive messages between the host computer and multiple EZT-430i controllers on the serial link. With a
default timeout period in EZT-430i of 135ms, it makes a total pause of 138ms minimum. Thus, after you
receive a response from an EZT-430i controller at your PC, you must wait a minimum of 138ms before
sending the next command.
4. Values containing decimal points such as process values and set points, have the decimal point implied,
i.e., the data exchange can only be performed using whole numbers. Thus, the value must be scaled
appropriately in order to exchange the data correctly. For example, a setpoint of 78.4 degrees must be
sent as a value of 784 in order for EZT-430i to be set correctly. Likewise, a process value read from EZT-
430i with a value of 827 is actually 82.7 degrees. Consult the parameter table for the proper format and
allowable range of each value.
5. When monitoring a process, try to keep the number of read and write commands to a minimum of 500ms
between exchanges to a single controller. Continuously reading data at a faster rate consumes an
excess amount of the controller’s processor time and does not provided any additional benefits in process
monitoring.
Handling Communication Errors
Messages with the wrong format or illegal values will receive an exception response. Messages with the
wrong CRC or timing will receive no response. It is the user’s responsibility to handle the error appropriately
within their own software and determine whether to resend the message or halt for operator intervention.
User Responsibility
Refrain from reading or writing from/to a register that does not exist or is currently disabled. Writing values to
unassigned registers could cause system instability, malfunction or failure. Care must also be taken in that
the process can not cause damage to property or injury to personnel if the wrong commands are sent due to
operator error or equipment malfunction.

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4.3.1 Packet Syntax
Each message packet begins with a one-byte controller address, from 0x01 to 0x1F. The second byte in the
message packet identifies the message command: read (0x03); write single (0x06) or write multiple (0x10).
The next “n” bytes of the message packet contain register addresses and/or data. The last two bytes in the
message packet contain a two-byte Cyclical Redundancy Checksum (CRC) for error detection.
Packet format:
address
command
registers and/or data
CRC
Read Register(s) Command (0x03)
This command returns from 1 to 60 registers. This command is used for reading one or more data locations
from EZT-430i .
Packet sent to EZT-430i :
controller address (1 byte)
read command (0x03)
starting register high byte
starting register low byte
number of registers high byte (0x00)
number of registers low byte
CRC low byte
CRC high byte
Packet returned from EZT-430i :
controller address (1 byte)
read command (0x03)
number of data bytes (1 byte)
first register data low byte
first register data high byte
…
…
register n data high byte
register n data low byte
CRC low byte
CRC high byte
nn nn nn nn… nn nn
nn 03 nn nn 00 nn nn nn
nn 03 nn nn nn … nn nn nn nn

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Example: Read registers 35 and 36 (loop 1 process variable and setpoint) of controller at address 1
configured for 1 decimal point.
Sent: 01 03 00 23 00 02 35 C1
Received: 01 03 04 03 0D 01 F3 2A 61
Message data: 781 (0x030D) = process variable of 78.1
499 (0x01F3) = setpoint of 49.9
Write Register Command (0x06)
This command writes a value to a single register. This command is to be used for setting control values in
EZT-430i . To set multiple values, repeat the command for each data location.
Packet sent to EZT-430i :
controller address (1 byte)
write command (0x06)
register high byte
register low byte
data high byte
data low byte
CRC low byte
CRC high byte
Packet returned from EZT-430i :
controller address (1 byte)
write command (0x06)
register high byte
register low byte
data high byte
data low byte
CRC low byte
CRC high byte
Example: Write register 41 (loop 2 set point) of controller at address one configured with no decimal point to
75 degrees (0x004B).
Sent: 01 06 00 29 00 4B 18 35
Received: 01 06 00 29 00 4B 18 35
Write Registers Command (0x10)
nn 06 nn nn nn nn nn nn
nn 06 nn nn nn nn nn nn

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This command writes values to multiple registers in sequential order. It is used for automatic program
download only to transmit program data one step at a time to EZT-430i . See the Automatic Program
Parameters section for the list of registers and their use. If this command is used to write to registers other
than the correct program step registers, EZT-430i will respond with an acknowledgment that the message
was received; however, the command will not be executed.
Packet sent to EZT-430i :
controller address (1 byte)
write command (0x10)
starting register high byte
starting register low byte
number of registers to write high byte
number of registers to write low byte
number of data bytes
data high byte
data low byte
…
…
register n data high byte
register n data low byte
CRC low byte
CRC high byte
Packet returned from EZT-430i :
controller address (1 byte)
write command (0x10)
starting register high byte
starting register low byte
number of registers to write high byte
number of registers to write low byte
CRC low byte
CRC high byte
Exception Responses
When EZT-430i cannot process a command, it returns an exception response and sets the high bit (0x80) of
the command.
0x01 illegal command
0x02 illegal data address
0x03 illegal data value
Packet returned from EZT-430i :
controller address (1 byte)
command + 0x80
exception code (0x01 or 0x02 or 0x03)
CRC low byte
CRC high byte
nn 10 nn nn nn nn nn nn nn … nn nn nn nn
nn 10 nn nn nn nn nn nn
nn nn nn nn nn

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4.3.2 Error Checking
In Modbus communications, every message sent from the master (your software) receives a response from
the slave (EZT-430i ), including write commands. Thus, after each command sent, you must read the
controller response before sending the next message. This provides the method of error checking in order to
verify that the message you sent was received correctly, and that the controller is operating accordingly. This
allows you to then determine the appropriate recovery response in case the message was not received
correctly by the controller, and what action is to be taken by an operator and/or the software itself.
The exception responses provide a basic form of error checking. When an exception response is received,
the code provided in the response will tell you what the error was in the sent message. However, this is only
valid if the controller receives the message you sent, and there was an out-of-range value or simple
transmission error in the message. It does not validate incomplete or failed transmissions. To insure that the
data you receive from a read command is correct, and that the controller properly received a write command,
you must parse the controller’s response and validate the return message to insure it is correct.
In order to validate that the message you received is correct, you must caulate the CRC for the received
message and compare it with the CRC that the controller appended to the message. This verifies that the
data you received was what EZT-430i sent. If the CRC’s do not match, there was an error in the transmission
and the entire message should be ignored. This could then be followed by an attempt to resend the failed
command, or halt operation and alert an operator.
Example: Read registers 35 and 36 (loop 1 process variable and setpoint) of controller at address 1.
Command sent to EZT-430i : 01 03 00 23 00 02 35 C1
Message received from EZT-430i : 01 03 04 03 0D 01 F3 2A 61
Caulated CRC: 2A61 (caulated from message 01 03 04 03 0D 01 F3)
Received CRC: 2A61
The caulated CRC matches the received CRC, the message is valid. Note that the last two bytes of
the received message are not used to caulate the CRC. The last two bytes are the CRC that EZT-
430i appended to the message. Do not include them when caulating the CRC.

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Transmitting and Receiving Messages
In order to reliably communicate with EZT-430i , it is important to develop an efficient means of transmitting
and receiving messages. Modbus is a structured protocol and it must be properly followed. It is
recommended, if possible, to locate an existing communication driver to incorporate into your software.
Developing one from scratch can be challenging. However, if one is not available, or you choose to develop
one yourself, the following guidelines may be of assistance.
Transmitting Messages
When sending a message to EZT-430i , it is important to remember that Modbus RTU protocol does not have
start-of-transmission or end-of-transmission characters. All messages are “framed” using timeouts between
characters. EZT-430i uses its own fixed timeout setting of 135ms. Thus, if the entire message is not received
by EZT-430i within 135ms, it will discard the data it has received and assume the next data byte received is
the start of the next valid message.
The timeout must be considered carefully when developing your application. In creating your message, there
are several steps that must be executed in order to build the packet and format the data properly into
hexadecimal to send out the serial port of your PC. If you write code in a manner that steps byte by byte
through sending the message out the serial port, formatting each piece of data prior to sending it, there is a
good possibility that two much time may pass between characters, thus causing a failed transmission.
Therefore, it is recommended that the entire message, including the CRC, be created and assembled prior to
being sent to the serial port. By assembling the main body of the message first, you can then pass it to the
CRC algorithm which can step sequentially through the message, generate the CRC and append it to the
message body. Once the message is completely assembled, it can then be sent out the serial port as a
completed packet. This will insure that the message reaches EZT-430i within the proper time frame.
Receiving Messages
Due to the fact that Modbus RTU protocol does not have start-of-transmission or end-of-transmission
characters, if the serial port driver you are using does not support an interval timeout setting allowing you to
automatically terminate a read after a specified time passes between bytes (signaling the end of a message),
you must know how long the message will be that you are receiving. That allows you to know how many
bytes to read from your serial port and when you have received the entire message. If you rely on a
maximum timeout period to terminate the read, depending upon the length of the received message, you will
either loose a portion of the message or have to set the timeout period so high, that it will greatly affect the
throughput of your code.
As can be seen from the previous examples for read and write commands in Section 4.3.1, the length of the
returned message will very based on the type of command, and for read commands, how many registers are
being returned. Response messages can vary in length from as little as 5 bytes for an exception response to
as many as 125 bytes for a read command. Therefore, in order to read in the message efficiently, you need
to know what type of command it is in response to.
The response messages are always coded with the first two bytes of the message as the controller address
and command type. When executing a read, read in only the first 2 bytes of data at the serial port. Examine
the second byte and determine what the command is. If it is a write command (0x06 or 0x10), you know the
response message is 8 bytes long. You can then read in the next 6 bytes of data from the serial port to
complete the message. You can then caulate the CRC for the first 6 bytes of that message, and compare it to
the last 2 bytes. If they match, then the communication completed successfully.
If the response is to a read command (0x03), you must then perform a single byte read from your serial port in
order to get the next byte of the message. The third byte in a read response message is the number of data
bytes in the message. By reading in this value, you then know how many data bytes follow. Note that this
value does not include the 2 bytes for the CRC. Thus, when reading in the rest of the message, you will read
in the number of data bytes plus an additional two, in order to get the CRC. You can then caulate the CRC
for the message and compare it to the last two bytes. If they match, the data you received is valid.