Trane Mobrus RTU TR1 Series User manual

TR1

Series VFD
Variable Frequency Drive
ModbusTM RTU
Instruction Manual
June, 2004 TR1-SVX02A-EN
175R5563

WARNING
!
Equipment Hazard!
Rotating shafts and electrical equipment
can be hazardous. Therefore, it is strongly
recommended that all electrical work
conform to National Electrical Code (NEC)
and all local regulations. Installation, start-
up and maintenance should be performed
only by qualified personnel. Failure to
follow the NEC or local regulations could
result in death or serious injury.
Motor control equipment and electronic controls are
connected to hazardous line voltages. When servicing
drives and electronic controls, there will be exposed
components at or above line potential. Extreme care
should be taken to protect against shock. Stand on an
insulating pad and make it a habit to use only one hand
when checking components. Always work with another
person in case of an emergency. Disconnect power
whenever possible to check controls or to perform
maintenance. Be sure equipment is properly grounded.
Wear safety glasses whenever working on electric
control or rotating equipment.
WARNING
!
Hazardous Voltage!
Touching electrical parts may be fatal, even after equipment has been
disconnected from the AC input line. To be sure that capacitors have fully
discharged, wait 14 minutes for 208 V and 480 V units and 30 minutes for 600 V
units over 25 hp after power has been removed before touching any internal
component. Failure to wait for capacitors to fully discharge before touching
internal components could result in death or serious injury.
CAUTION
Electrostatic Discharge!
Electronic circuit card components are
sensitive to electrostatic discharge (ESD).
ESD can reduce performance or destroy
sensitive electronic components. Follow
proper ESD procedures during installation
or servicing to prevent damage.
WARNING
!
Unintended Start!
In Auto Mode, a start signal via digital
inputs may cause drive to start at any time.
The drive, motor, and any driven equipment
must be in operational readiness. Failure
to be in operational readiness in Auto Mode
could result in death, serious injury, or
equipment or property damage.

3
Table of Contents
Overview
Introduction ............................................................................................ 4
About This Manual.................................................................................. 4
Assumptions ........................................................................................... 4
What You Should Already Know ........................................................... 4
References .............................................................................................. 4
Modbus RTU Overview .......................................................................... 5
TR1 Series VFD with Modbus RTU Option Overview ............................. 5
Network Connection
Network Connection ................................................................................ 6
Drive DIP Switch Settings for Network Connection ............................... 6
Drive Parameter Settings for Modbus RTU Communication ................. 6
Network Configuration
Remote Terminal Unit .............................................................................. 7
Modbus RTU Message Structure ............................................................ 7
Memory Mapping: Coils ......................................................................... 9
Memory Mapping: Holding Registers .................................................... 11
Memory Mapping: Numbering ............................................................... 12
Conversion Index and Data Type ............................................................. 12
Communication Examples
Standard Modbus Functions .................................................................. 13
Example 1 Start the Drive and Give It a Reference via Modbus RTU .. 14
Example 2 Give the Drive a Reference via Modbus RTU ..................... 15
Example 3 Read Basic Drive Status Information ................................. 16
Example 4 Give the Drive a Ramp to Stop Command ......................... 18
Example 5 Give the Drive a Coast to Stop Command ......................... 19
Example 6 Set How the Drive Stores Parameter Values ...................... 20
Example 7 Write a Parameter Value from a List of Choices ................ 21
Example 8 Write a 16 Bit Parameter ...................................................... 22
Example 9 Write a 32 Bit Parameter ...................................................... 23
Example 10 Read a 32 Bit Parameter .................................................... 24
Example 11 Read Indexed Parameter and Read 8 Bit Parameter ....... 25
Example 12 Write a Text String .............................................................. 27
Example 13 Read a Text String .............................................................. 28
Exception Codes ..................................................................................... 29

4
This manual is intended to be used for both
instruction and reference. It only briefly
describes the basics of the Modbus protocol
whenever necessary to gain an understanding
of the Modbus RTU for the TR1 Series VFD.
This manual is also intended to serve as a
guideline when you specify and optimize your
communication system. Even if you are an
experienced Modbus programmer, it is
Introduction
About This
Manual
What You
Should
Already Know
Assumptions
This manual provides comprehensive
instructions on the set up and operation of
the Modbus RTU protocol for the TR1 Series
VFD variable frequency drive to communicate
over a Modbus network.
The TR1 Series VFD Modbus RTU is designed
to communicate with any controller that
supports the interfaces defined in this
document. It is assumed that you have full
knowledge of the capabilities and limitations
of the controller.
This manual assumes that you have a
controller that supports the interfaces in this
document and that all the requirements
stipulated in the controller, as well as the TR1
Series VFD, are strictly observed, along with
all limitations therein.
suggested that you read this manual in its
entirety before you start programming since
important information can be found in all
sections.
References TR1TM Series VFD Installation and Operation
Manual, document number TR1-SVX10A-EN.
For specific information on installation and
operation of the variable frequency drive, refer
to the TR1 Series VFD Installation and
Operation Instruction Manual.

5
Modbus RTU
Overview
The common language used by all Modicon
controllers is the Modbus RTU (Remote
Terminal Unit) protocol. This protocol defines
a message structure that controllers will
recognize and use, regardless of the type of
networks over which they communicate. It
describes the process a controller uses to
request access to another device, how it
will respond to requests from the other
devices, and how errors will be detected
and reported. It establishes a common
format for the layout and contents of
message fields.
During communications on a Modbus RTU
network, the protocol determines how each
controller will know its device address,
recognize a message addressed to it,
determine the kind of action to be taken,
and extract any data or other information
contained in the message. If a reply is
required, the controller will construct the reply
message and send it.
Controllers communicate using a master-
slave technique in which only one device
(the master) can initiate transactions (called
queries). The other devices (slaves) respond
by supplying the requested data to the
master, or by taking the action requested in
the query.
The master can address individual slaves, or
can initiate a broadcast message to all slaves.
Slaves return a message (called a response)
to queries that are addressed to them
individually. Responses are not returned to
broadcast queries from the master.
The Modbus RTU protocol establishes the
format for the master’s query by placing into
it the device (or broadcast) address, a
function code defining the requested action,
any data to be sent, and an error-checking
field. The slave’s response message is also
constructed using Modbus protocol. It
contains fields confirming the action taken,
any data to be returned, and an error-
checking field. If an error occurs in receipt of
the message, or if the slave is unable to
perform the requested action, the slave will
construct an error message and send it in
response, or a timeout will occur.
TR1 Series
VFD with
Modbus RTU
Option
Overview
The TR1 Series variable frequency drive
communicates in Modbus RTU format over
an EIA-485 (formerly RS-485) network.
Modbus RTU allows access to the drive
Control Word and Bus Reference.
The Control Word allows Modbus to control
several important functions of the drive:
• Start
• Stop (in several ways):
Coast stop
Quick stop
DC Brake stop
Normal (ramp) stop
• Reset after a fault trip
• Run at a variety of preset speeds
• Run in reverse
• Change the active setup
• Control the drive's two built-in relays
The Bus Reference is commonly used for
speed control.
It is also possible to access the drive
parameters, read their values, and, where
possible, write values to them. This permits
a range of control possibilities, including
controlling the drive setpoint when its internal
PID controller is used.

6
The Modbus RTU interface to the TR1 Series
VFD requires drive parameter values selected
as shown. See the TR1 Series VFD Installation
and Operation Manual for details on selecting
and changing parameter values, if necessary.
Drive
Parameter
Settings for
Modbus RTU
Communica-
tion • Parameter 500, Protocol: Modbus RTU
• Parameter 501, Address: 001 - 247
• Parameter 502, Baud Rate: 300 - 9600
baud. (Factory default is 9600 baud.)
• Parameter 570, Modbus Parity/Frame:
select from the following, based on
application.
Even Parity/1 Stop
Odd Parity/1 Stop
No Parilty/1 Stop (factory default)
• Parameter 571, Modbus Communication
Timeout: 10 - 2000 ms. (Factory default
setting is 100 ms.)
Network
Connection
EIA-485 Connector
RTxD' (-)
RTxD (+)
COM
69
68
61
Pin 1
Connect the Modbus RTU control wiring to
drive terminals (+)68 and (-)69 on control card
as illustrated.
Use 18 - 24 AWG (1.5 mm) shielded, twisted
pair control wiring. Tighten to 4.5 in-lbs (0.5
Nm).
Shielded wiring must be used. Ground shield
to drive terminal 61, drive casing, or as
appropriate for the network application.
DIP switches 2 and 3, located on the main
control board of the drive directly above the
EIA-485 connector, can be used to terminate
drives on the Modbus network (see figure). In
addition to serial communication, switch 4 is
used to isolate a low voltage, external DC
power supply. The factory default switch
positions are ON (see table).
Drive DIP
Switch
Settings for
Network
Connection
Drive DIP Switches
SWITCH SETTING
Switch 1 No function
Switches 2 & 3 Used for terminating an EIA-485 interface. When
the drive is the first, last, or only device on a
network, switches 2 and 3 must be ON.
When the drive is in any other location on the
network, switches 2 and 3 must be OFF.
Switch 4 Separates the common potential of the internal 24
VDC supply from the common potential of external
24 VDC supply. When switch 4 is in the OFF
position, the external 24 VDC supply is isolated
from the drive. See the drive operation manual for
more information on switch 4.
Drive DIP Switche Settings

7
Modbus RTU
Message
Framing
Structure
The controllers are setup to communicate on
the Modbus network using RTU (Remote
Terminal Unit) mode, with each 8-bit byte in a
Coding System: 8-bit binary, hexadecimal 0-9, A-F
Two hexadecimal characters contained in each 8-bit
field of the message
Bits Per Byte: 1 start bit
8 data bits, least significant bit sent first
1 bit for even/odd parity; no bit for no parity
1 stop bit if parity is used; 2 bits if no parity
Error Check Field: Cyclical Redundancy Check (CRC)
A Modbus RTU message is placed by the
transmitting device into a frame with a known
beginning and ending point. This allows
receiving devices to begin at the start of the
message, read the address portion, determine
which device is addressed (or all devices, if
the message is broadcast), and to know when
the message is completed. Partial messages
are detected and errors set as a result.
The allowable characters transmitted for all
fields are hexadecimal 0-9, A-F. The adjustable
frequency drives monitor the network bus
continuously, including ‘silent’ intervals. When
the first field (the address field) is received, each
drive or device decodes it to determine
whether it is the addressed device.
Modbus RTU messages addressed to zero
are broadcast messages. No response is
needed on broadcast messages.
To ensure the attribute data returned is the
most current, each attribute access must
include one attribute only.
A typical message frame is shown below.
Start Address Function Data CRC Check End
T1-T2-T3-T4 8 Bits 8 Bits
n x 8 Bits 16 Bits T1-T2-T3-T4
Remote
Terminal
Unit
Start/Stop Field
Messages start with a silent interval of at least
3.5 character times. This is implemented as a
multiple of character times at the selected
network baud rate (shown as Start T1-T2-
T3-T4). The first field then transmitted is the
device address. Following the last transmitted
character, a similar interval of at least 3.5
character times marks the end of the
message. A new message can begin after
this interval.
The entire message frame must be transmitted
as a continuous stream. If a silent interval of
more than 1.5 character times occurs before
completion of the frame, the receiving device
flushes the incomplete message and assumes
that the next byte will be the address field of a
new message.
Similarly, if a new message begins earlier that
3.5 character times following a previous
message, the receiving device will consider it
a continuation of the previous message. This
will cause a timeout (no response from the
slave), since the value in the final CRC field is
not valid for the combined messages.
Typical Modbus RTU Message Structure
Modbus RTU
Message
Framing
Structure
(continued)
message contains two 4-bit hexadecimal
characters. The format for each byte is shown
below.

8
Address Field
The address field of a message frame contains
8 bits. Valid slave device addresses are in the
range of 0 – 247 decimal. The individual slave
devices are assigned addresses in the range
of 1 – 247. (0 is reserved for broadcast mode,
which all slaves recognize.) A master
addresses a slave by placing the slave address
in the address field of the message. When
the slave sends its response, it places its own
address in this address field to let the master
know which slave is responding.
Function Field
The function field of a message frame contains
8 bits. Valid codes are in the range of 1 – 255
decimal. When a message is sent from a
master to a slave device, the function code
field tells the slave what kind of action to
perform.
When the slave responds to the master, it
uses the function code field to indicate either
a normal (error-free) response, or that some
kind of error occurred (called an exception
response). For a normal response, the slave
simply echoes the original function code. For
an exception response, the slave returns a
code that is equivalent to the original function
code with its most-significant bit set to a logic
1. In addition, the slave places a unique code
into the data field of the response message.
This tells the master what kind of error
occurred, or the reason for the exception. See
the Exception Codes section in this manual
for definitions.
Data Field
The data field is constructed using sets of two
hexadecimal digits, in the range of 00 to FF
hexadecimal. These are made from one RTU
character. The data field of messages sent
from a master to slave device contains
additional information which the slave must
use to take the action defined by the function
code. This can include items like coil or register
addresses, the quantity of items to be handled,
and the count of actual data bytes in the field.
The data field can have a length of zero.
CRC Check Field
Messages include an error-checking field that
is based on a cyclical redundancy check (CRC)
method. The CRC field checks the contents
of the entire message. It is applied regardless
of any parity check method used for the
individual characters of the message. The CRC
value is calculated by the transmitting device,
which appends the CRC as the last field in
the message. The receiving device
recalculates a CRC during receipt of the
message and compares the calculated value
to the actual value received in the CRC field.
If the two values are not equal, a bus timeout
results.
The error checking field contains a 16-bit binary
value implemented as two 8-bit bytes. When
this is done, the low-order byte of the field is
appended first, followed by the high-order byte.
The CRC high-order byte is the last byte sent
in the message.
Coil/Register Addressing
All data addresses in Modbus messages are
referenced to zero. The first occurrence of a
data item is addressed as item number zero.
For example:
The coil known as ‘coil 1’ in a programmable
controller is addressed as coil 0000 in the data
address field of a Modbus message. Coil 127
decimal is addressed as coil 007EHEX (126
decimal).
Holding register 40001 is addressed as register
0000 in the data address field of the message.
The function code field already specifies a
‘holding register’ operation. Therefore, the
‘4XXXX’ reference is implicit. Holding register
40150 is addressed as register 0095BHEX (149
decimal).
Modbus RTU
Message
Framing
Structure
(continued)

9
Memory
Mapping:
Coils
This is primarily used to control drive operation
and to read out basic status information.
Coil 65 determines whether parameter
changes made via Modbus RTU are held in
the temporary memory (RAM) of the drive or
are, in addition, written to permanent memory
(EEPROM).
Coil
Number Description Signal Direction
1 – 16 Drive Control Word (see table) Master to Drive
17 - 32 Drive Speed or Setpoint Reference
0HEX = 0% Reference, the value set in
parameter 204.
4000HEX = 100% Reference, the value
set in parameter 205.
8000HEX = 200% Reference, the
maximum value that can be
transmitted via Modbus RTU.
In most cases, if references from multiple
sources are supplied to the drive, the drive
will respond to the sum of the references
Master to Drive
33 – 48 Drive Status Word (see table) Drive to Master
49 – 64 Open Loop Mode: Drive Output
Frequency
0HEX = 0% of the reference value set in
parameter 204.
4000HEX = 100% of the reference value
set in parameter 205.
Closed Loop Mode: Drive Feedback
Signal
0HEX = 0% of the reference value set in
parameter 204.
4000HEX = 100% of the Reference value
set in parameter 205.
Drive to Master
65 Parameter Write Control (Master to Drive)
0
Î
Parameter changes are written to
the drive’s RAM and are lost when
power is removed from the drive.
1
Î
Parameter changes are written to
the drive RAM and to its EEPROM
and are maintained when power is
removed from the drive.
Master to Drive
66 - 65536 Reserved

10
Coil 0 1
01 Preset Ref. LSB
02 Preset Ref. MSB
03 DC Brake No DC Brake
04 Coast stop No coast stop
05 Quick stop No quick stop
06 Freeze freq. No freeze freq.
07 Ramp stop Start
08 No reset Reset
09 No j og Jog
10 no function
11 Data not valid Data valid
12 Relay 1 OFF Relay 1 ON
13 Relay 2 OFF Relay 2 ON
14 Setup LSB
15 Setup MSB
16 No reversing Reversing
Memory
Mapping:
Coils
(continued)
Coil 0 1
33 Control not ready Control ready
34 Drive not ready Drive ready
35 Coasting Stop Safety closed
36 No alarm Alarm
37 Not in use
38 Not in use
39 Not in use
40 No warning Warning
41 Not at reference At reference
42 Hand mode Auto mode
43 Out of frequency range In frequency range
44 Stopped Running
45 No function No function
46 No voltage warning Voltage warning
47 Not in current limit Current limit
48 No thermal warning Thermal warning
Control Word Coil Description
Status Word Coil Description
Stop Commands
The precedence of the stop
commands is as follows:
1. Coast stop
2. Quick stop
3. DC Brake
4. Normal (Ramp) stop