User’s manual
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Lexium Controller
Modbus
Contents
Important information _________________________________________________________________________________________ 4
Documentation structure_______________________________________________________________________________________ 5
Introduction_________________________________________________________________________________________________ 6
Presentation _____________________________________________________________________________________________ 6
Connection to the bus_________________________________________________________________________________________ 7
Connecting the Modbus RJ45 connector or graphic display terminal__________________________________________________ 7
Connecting to the Lexium Controller __________________________________________________________________________ 7
Wiring recommendations ___________________________________________________________________________________ 7
RS485 standard __________________________________________________________________________________________ 7
Modbus standard schematic_________________________________________________________________________________ 8
Connecting via RJ45 wiring system ___________________________________________________________________________ 9
Connecting via junction boxes ______________________________________________________________________________ 11
Connecting on screw terminals______________________________________________________________________________ 13
Configuration ______________________________________________________________________________________________ 14
Configuring the Modbus network ____________________________________________________________________________ 14
Diagnostics ________________________________________________________________________________________________ 16
Modbus LEDs ___________________________________________________________________________________________ 16
Communication management and communication interruptions ____________________________________________________ 16
Modbus protocol ____________________________________________________________________________________________ 17
RTU mode _____________________________________________________________________________________________ 17
Principle _______________________________________________________________________________________________ 17
Addresses______________________________________________________________________________________________ 17
Modbus functions ________________________________________________________________________________________ 18
Read N output words: function 3 ____________________________________________________________________________ 18
Write one output word: function 6 ____________________________________________________________________________ 19
Diagnostics: function 8 ____________________________________________________________________________________ 19
Write N output words: function 16 (16#10) _____________________________________________________________________ 20
Identification: function 43 (16#2B) ___________________________________________________________________________ 21
Exception responses _____________________________________________________________________________________ 22
Read non-existent or protected parameters ____________________________________________________________________ 22
While every precaution has been taken in the preparation of this document,
Schneider Electric assumes no liability for any omissions or errors it may contain, nor for any damages resulting from the application or use of the information herein.
The products and options described in this document may be changed or modified at any time, either from a technical point of view or in the way they are operated. Their description can in no way be considered contractual.
3
4
Important information
PLEASE NOTE
Please read these instructions carefully and examine the equipment in order to familiarize yourself with the device before installing, operating or carrying out any maintenance work on it.
The following special messages that you will come across in this document or on the device are designed to warn you about potential risks or draw your attention to information that will clarify or simplify a procedure.
The addition of this symbol to a "Danger" or "Warning" safety label indicates the presence of an electrical hazard that will result in injury if the instructions are not followed.
This is a safety warning symbol. It warns you of potential risks of injury. You must comply with all safety messages that follow this symbol in order to avoid any risk of injury or death.
DANGER
DANGER indicates an imminently hazardous situation which, if not avoided, will result in death, serious injury or equipment damage.
WARNING
WARNING indicates a potentially hazardous situation which, if not avoided, can result in death, serious injury or equipment damage.
CAUTION
CAUTION indicates a potentially hazardous situation which, if not avoided, can result in injury or equipment damage.
PLEASE NOTE:
Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. No responsibility is assumed by
Schneider Electric for any consequences arising out of the use of this material.
BLMT00016 © 2008 Schneider Electric. All rights reserved.
WARNING
LOSS OF CONTROL
- The designer of any control scheme must consider the potential failure modes of control paths and, for certain critical control functions, must provide a means to achieve a safe state during and after a path failure. Examples of critical control functions are emergency stop and overtravel stop.
- Separate or redundant control paths must be provided for critical control functions.
- System control paths may include communication links. Consideration must be given to the implications of unanticipated transmission delays or failures of the link.
1
- Each implementation of a Lexium Motion Controller must be individually and thoroughly tested for proper operation before being placed into service.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
1. For additional information refer to NEMA ICS 1.1 (latest edition), "Safety Guidelines for the Application, Installation, and Maintenance of Solid State Control"
Documentation structure
This manual is part of a series describing the Lexium Motion Controller (LMC). The following manuals may be downloaded at www.us.telemecanique.com
Installation Manual
This manual describes:
• How to install the controller
• How to connect the controller
Optional Graphic Display Terminal User's Manual
This manual describes:
• How to install the graphic display terminal
• How to connect the graphic display terminal
• How to program the controller via the graphic display terminal
EasyMotion - Programming Manual (Not available in the USA)
Supplied preinstalled in the Lexium Controller, the application model associated with Easy Motion mode is a user-friendly tool that can be used for:
• Rapid axis configuration
• Use of Manual/Automatic mode
• Creating positioning tasks
• Editing cam profiles
• Backup and recovery of the machine parameters
• Diagnostics of the motion controller and the various axes
This programming manual also contains a table of the parameters that can be accessed via the communication protocols.
MotionPro - Programming Manual
The Motion Pro Programming Manual is included in the software online help.
This online help describes:
• The software interface
• IEC 1131 programming
• The function libraries (standard functions, motion control functions, application functions)
• The Lexium controller configuration screens
Modbus, Ethernet, PROFIBUS DP, and DeviceNet manuals
These manuals describe:
• Connection to the bus or network
• Diagnostics
• Software setup
• The protocol communication services
5
6
Introduction
Presentation
The integrated communication port provides direct access to the Modbus protocol:
• The Modbus HMI RJ45 port, located on the front panel of the Lexium Controller is used to connect:
- The graphic display terminal
- A Magelis industrial HMI terminal
- A programmable controller (PLC)
- Another controller
- The Motion Pro/CoDeSys software workshop
The Modbus port on the Lexium Controller can be used for the following functions:
• Configuration
• Adjustment
• Control
• Monitoring
The Lexium Controller supports:
• The 2-wire RS485 physical layer
• RTU transmission mode
This manual describes how to set up the Lexium Controller on Modbus and the available Modbus services.
The slave address is configured using Motion Pro/CoDeSys
The Modbus network speed is 38.4 kbps.
It can be configured for 19.2, but this configuration limits use with Motion Pro/CoDeSys via the serial link.
LMC10/LMC20
LMC20A****
Modbus connector or graphic display terminal
Connection to the bus
Connecting the Modbus RJ45 connector or graphic display terminal
Connector on Lexium
Controller
1.......................8
MODBUS
Terminal
1
2
5
6
3
4
7
8
Description
not connected not connected not connected
B signal (RS485) = V1 signal (Modbus)
A signal (RS485) = V0 signal (Modbus) not connected
Modbus VP signal
12 V DC power supply provided by the Motion Controller (only for the power supply of an
RS485/RS232 converter or a graphic display terminal)
Modbus common signal
0V
Note: Do not use terminals marked "not connected".
Connecting to the Lexium Controller
Connection accessories must be ordered separately (please refer to the catalogs).
Connect the RJ45 cable to the "MODBUS" port on the Lexium Controller
Wiring recommendations
• Use the Telemecanique cable with 2 pairs of shielded twisted conductors (references: TSXCSA100, TSXCSA200 or TSXCSA500).
• The Modbus cable must be at least 30 cm away from the power cables.
• If it is necessary to cross the Modbus cables and the power cables, be sure they cross at right angles.
• As far as possible, connect the shielded cable to a protective ground, for example to the ground of each device if this ground is connected to the protective ground.
• Install a line terminator at each end of the line.
• Check the polarity of the line.
• Connect the common ("common" signal) to the protective ground at one or more points on the bus.
For more information, refer to the "Electromagnetic compatibility of industrial networks and fieldbuses" manual.
Cable routing practices
When wiring Lexium Controller to a Modbus network, follow all wiring practices required by national and local electrical codes. Also observe the following guidelines:
• Avoid areas of high temperature, moisture, vibration, or other mechanical stress.
• Secure the cable where necessary to prevent its weight and the weight of other cables from pulling or twisting the cable.
• Use cable ducts, raceways, or other structures to protect the cable. Use these structures for signal wiring paths. They must not contain power wiring.
• Avoid sources of electrical interference that can induce noise into the cable. Use the maximum practicable separation from such sources.
When planning cable routing within a building, follow these guidelines:
• Maintain a minimum separation of 1 m (3.28 ft) from sources of electromagnetic interference, such as:
- air conditioners and large blowers,
- elevators and escalators,
- radios and televisions,
- intercom and security systems,
- fluorescent, incandescent, and neon lighting fixtures.
• Maintain a minimum separation of 3 m (9.84 ft) from stronger electromagnetic interference generating equipment, such as:
- line and motor power wiring,
- transformers,
- generators,
- alternators.
7
8
Connection to the bus
When wiring in electrical equipment rooms or large electrical equipment line-ups, observe the following guidelines for cable segregation and separation of circuits:
• Use metallic conduit for Lexium Controller wiring. Do not run control network and power wiring in the same conduit.
• Separate non-metallic conduits or cable trays used to carry power wiring from metallic conduit carrying low-level control network wiring by at least 300 mm (11.8 in).
• Separate metallic conduits carrying power wiring or low-level control network wiring by at least 80 mm (3.15 in).
• Cross the metallic conduits and non-metallic conduits at right angles whenever power and control network wiring cross.
• Attenuate conducted emissions from the Lexium Controller to the line in some installations to prevent interference with telecommunication, radio, and sensitive electronic equipment. Such instances may require attenuating filters. Consult the Lexium
Controller catalog for selection and application of these filters.
RS485 standard
The RS485 standard allows variants of different characteristics:
• Polarity
• Line termination
• Distribution of a reference potential
• Number of slaves
• Length of bus
The new Modbus specifications, published on www.modbus.org in 2002 gives precise details of all these characteristics. They are also summarized in the next section (standard schematic). The new Telemecanique devices comply with these specifications.
Connection to the bus
Modbus standard schematic
The standard schematic corresponds to the Modbus specification published in 2002 on www.modbus.org
(Modbus_over_serial_line_V1.pdf, Nov 2002) and, in particular, to the 2-wire multipoint serial bus schematic.
The Lexium Controller conforms to this specification.
Schematic diagram:
Master
R
650
Ω
0 V
T
5 V
650
Ω
D1
120
Ω
1n F
D0
Common
120
Ω
1n F
R
T
Slave 1
R
T
Slave n
Type of trunk cable
Maximum length of bus
Maximum number of stations (without repeater) 32 stations, i.e., 31 slaves
Maximum length of tap links • 20 m (65.62 ft) for one tap link
• 40 m (131.23 ft) divided by the number of tap links on a multiple junction box
Bus polarization
Shielded cable with 1 twisted pair and at least a 3rd conductor
1000 m at 19200 bps with the Telemecanique TSX CSA
*
cable
Line termination
Common polarity
• One 450 to 650
Ω
pull-up resistor to the 5 V (650
Ω
or thereabouts recommended)
• One 450 to 650
Ω
pull-down resistor to the Common (650
Ω
or thereabouts recommended)
This polarization is recommended for the master.
One 120
Ω
0.25 W resistor in series with a 1nF 10 V capacitor
Yes (Common), connected to the protective ground at one or more points on the bus
9
Connection to the bus
Connecting via RJ45 wiring system
1
- Master (PLC, PC or communication module)
2
- Modbus cable depending on the type of master (see table page 11 )
3
- Modbus splitter box LU9 GC3
4
- Modbus drop cables VW3 A8 306 R**
5
- Line terminators VW3 A8 306 RC
6
- T-junction boxes VW3 A8 306 TF** (with cable)
7
- Modbus cable (to another splitter box) TSX CSA*00
LMC
Connection accessories
Description
Modbus splitter box
Modbus T-junction boxes
Line terminators
For RJ45 connector
10 RJ45 connectors and 1 screw terminal
With integrated cable (0.3 m)
With integrated cable (1 m)
R = 150 Ω
Connection cables
Description Length (m)
Cables for
Modbus bus
RS 485 double shielded twisted pair cables
1
3
3
0.3
100
200
500
Connectors
1 RJ45 connector and 1 stripped end
2 RJ45 connectors
2 RJ45 connectors
2 RJ45 connectors
Supplied without connector
Supplied without connector
Supplied without connector
6
6
5
No.
3
Reference
LU9 GC3
VW3 A8 306 TF03
VW3 A8 306 TF10
VW3 A8 306 R
No.
7
7
7
4
4
4
Reference
VW3 A8 306 D30
VW3 A8 306 R03
VW3 A8 306 R10
VW3 A8 306 R30
TSX CSA 100
TSX CSA 200
TSX CSA 500
10
Connection to the bus
Type of master
Twido PLC
TSX Micro PLC
TSX Premium PLC
Master interface Modbus connection accessories for RJ45 wiring system
Description Reference
TWD XCA RJ030 Adaptor or mini-DIN
RS485 interface module
Adaptor or screw terminal RS485 interface module
3 m cable equipped with a mini-DIN connector and an
RJ45 connector
3 m cable equipped with an RJ45 connector and stripped at the other end
Mini-DIN RS485 connector port
PCMCIA card
(TSX SCP114)
TSX SCY 11601 or TSX
SCY 21601 module
(25-way SUB-D socket)
3 m cable equipped with a mini-DIN connector and an
RJ45 connector
Stripped cable
Cable equipped with a 25-way SUB-D connector and stripped at the other end (for connection to the screw terminals of the LU9GC3 splitter box)
PCMCIA card
(TSX SCP114)
Stripped cable
Screw terminal RS485 3 m cable equipped with an RJ45 connector and stripped at the other end
RJ45 RS485 1 m cable equipped with 2 RJ45 connectors
VW3 A8 306 D30
TWD XCA RJ030
TSX SCP CM 4030
TSX SCY CM 6030
TSX SCP CM 4030
VW3 A8 306 D30
VW3 P07 306 R10
Ethernet bridge
(174 CEV 300 10)
PROFIBUS DP gateway
(LA9P307)
Fipio (LUFP1) or
PROFIBUS DP (LUFP7) or
DeviceNet (LUFP9) gateway
PC with serial port
RJ45 RS485
PC with male 9-way
SUB-D RS232 serial port
0.3 m cable equipped with 2 RJ45 connectors or
1 m cable equipped with 2 RJ45 connectors or
3 m cable equipped with 2 RJ45 connectors
RS232/RS485 converter and 3 m cable equipped with an RJ45 connector and stripped at the other end (for connection to the screw terminals of the LU9GC3 splitter box)
VW3 A8 306 R03 or
VW3 A8 306 R10 or
VW3 A8 306 R30
TSX SCA 72 and
VW3 A8 306 D30
11
Connection to the bus
Connecting via junction boxes
1
2 5
6
3 4
7
1
- Master (PLC, PC or communication module)
2
- Modbus cable depending on the type of master (see table page 13 )
3
- Modbus cable TSX CSA*00
4
- Junction box TSX SCA 50
5
- Subscriber socket TSX SCA 62
6
- Modbus drop cable VW3 A8 306
7
- Modbus drop cable VW3 A8 306 D30
LMC
Connection accessories
Description
Junction box
3 screw terminals and an RC line terminator, to be connected using cable VW3 A8 306 D30
Subscriber socket
2 female 15-way SUB-D connectors, 2 screw terminals, and an RC line terminator, to be connected using cable VW3 A8 306 or VW3 A8 306 D30
No.
4
5
Reference
TSX SCA 50
TSX SCA 62
Connection cables
Description Length (m)
Cables for Modbus bus 3
3
RS 485 double shielded twisted pair cables
100
200
500
Connectors
1 RJ45 connector and one stripped end
1 RJ45 connector and 1 male 15-way SUB-D connector for
TSX SCA 62
Supplied without connector
Supplied without connector
Supplied without connector
3
3
3
No.
7
6
Reference
VW3 A8 306 D30
VW3 A8 306
TSX CSA 100
TSX CSA 200
TSX CSA 500
12
Connection to the bus
Type of master
Twido PLC
TSX Micro PLC
TSX Premium PLC
Ethernet bridge
(174 CEV 300 10)
PROFIBUS DP gateway
(LA9P307)
Fipio (LUFP1) or
PROFIBUS DP (LUFP7) or
DeviceNet (LUPF9) gateway
PC with serial port
Master interface
Adaptor or screw terminal
RS485 interface module
Mini-DIN RS485 connector port
PCMCIA card (TSX SCP114)
TSX SCY 11601 or
TSX SCY 21601 module
(25-way SUB-D socket)
PCMCIA card (TSX SCP114)
Screw terminal RS485
RJ45 RS485
RJ45 RS485
PC with male 9-way SUB-D
RS232 serial port
Modbus connection accessories for junction boxes using screw terminals
Description
Modbus cable
Reference
TSX CSA100 or
TSX CSA200 or
TSX CSA500
Junction box TSX P ACC 01
Cable equipped with a special connector and stripped at the other end
Cable equipped with a 25-way SUB-D connector and stripped at the other end
TSX SCP CU 4030
TSX SCY CM 6030
Cable equipped with a special connector and stripped at the other end
Modbus cable
TSX SCP CU 4030
TSX CSA100 or
TSX CSA200 or
TSX CSA500
VW3 A8 306 D30 3 m cable equipped with an RJ45 connector and stripped at the other end
3 m cable equipped with an RJ45 connector and stripped at the other end
VW3 A8 306 D30
RS232/RS485 converter and
Modbus cable
TSX SCA 72 and
TSX CSA100 or
TSX CSA200 or
TSX CSA500
Type of master
Twido PLC
TSX Micro PLC
TSX Premium PLC
Ethernet bridge
(174 CEV 300 10)
PROFIBUS DP gateway
(LA9P307)
Fipio gateway (LUFP1) or
PROFIBUS DP gateway
(LUFP7)
PC with serial port
Master interface
Adaptor or screw terminal RS485 interface module
TSX SCY 11601 or
TSX SCY 21601 module
(SUB-D 25 socket)
PCMCIA card (TSX SCP114)
Screw terminal RS485
-
Modbus connection accessories for junction boxes using
SUB-D 15
Description
Mini-DIN RS485 connector port -
PCMCIA card (TSX SCP114) Cable equipped with a special connector and a SUB-D 25 connector
Cable equipped with a 25-way SUB-D connector and stripped at the other end
-
Cable equipped with a special connector and stripped at the other end
-
-
-
Reference
TSX SCY CU 4530
TSX SCP CU 4530
TSX SCY CU 4530
RJ45 RS485
RJ45 RS485 3 m cable equipped with an RJ45 connector and a SUB-D 25 connector
VW3 A8 306
PC with male 9-way SUB-D
RS232 serial port
-
13
Connection to the bus
Connecting on screw terminals
Connection accessories
Description
Line terminators
For screw terminals
Connection cables
Description
Cables for
Modbus bus
RS 485 double shielded twisted pair cables
Length (m)
3
100
200
500
R = 150
Ω
Reference
VW3 A8 306 DR
Connectors
1 RJ45 connector and one stripped end
Supplied without connector
Supplied without connector
Supplied without connector
Reference
VW3 A8 306 D30
TSX CSA 100
TSX CSA 200
TSX CSA 500
14
Configuration
Configuring the Modbus network
The parameters of the Modbus network can be configured via the graphic display terminal or using the Motion Pro/CoDeSys software.
Configuration via the graphic display terminal
The parameters [Modbus address] and [Modbus baudrate] are available in the sub-menu
[LC CONFIGURATION]
.
Modbus parameter
[Modbus address]
[Modbus baudrate]
Description/Possible values
1 to 247
0 = Lexium Controller Modbus server disabled
Baudrate of Modbus communication
Terminal display
Default value
[1]
to
[247]
[0]
[0]
[9600]
,
[19200]
,
[38400] [38400]
NOTE:
The graphic display terminal will only operate at 38400 bps and the value 8-N-1 (8 bits sent - no parity - 1 stop bit).
Any other value will make communication with the graphic display terminal impossible.
Configuration using the Motion Pro/CoDeSys software
The configuration can be read via the PLC-Browser key word.
The key word for ascertaining the address and speed of the Modbus network is mbusinf.
15
Configuration
The key word for configuration of the Modbus network address is, for example with address 2: mbaddr 2
16
Diagnostics
Modbus LEDs
The Modbus LEDs are located on the RJ45 port, on the front panel of the Lexium Controller. They indicate the Modbus communication status.
STATUS
LED
Each LED lights up for 200 ms when a frame is being transmitted on the corresponding Modbus network, whether or not this is destined for the Lexium Controller.
Communication management and communication interruptions
If there is no Modbus communication, the LEDs on the graphic display terminal are off.
There is no specific Modbus communication interruption LED.
• Following initialization (power-up), the Lexium Controller checks that frames are being sent on the Modbus network. These frames can be sent from a Modbus PLC or an HMI, and also from a PC on which the Motion Pro/CoDeSys software is running.
If the cable is disconnected from the Modbus master, then reconnected in order to communicate using the Motion Pro/CoDeSys software, the Lexium Controller automatically detects the Motion Pro/CoDeSys frame format with no action required from the user.
It is possible to reconnect to the Modbus Master again with no action required from the user.
• Thus, when a Modbus communication interruption occurs, the Lexium Controller does not react. The communication interruption must be managed by the Modbus Master, from a PLC, a PC, an industrial terminal (Magelis), or a SCADA monitoring the Lexium Controller.
17
Modbus protocol
RTU mode
RTU transmission mode is used. The frame contains no message header byte and no end of message byte.
It is defined as follows:
Slave address
Request code Data
The data is transmitted in binary code.
CRC16: Cyclic redundancy check parameter.
The end of the frame is detected on a silence greater than or equal to 3.5 characters.
CRC16
Principle
The Modbus protocol is a master-slave protocol.
Master
Only one device can transmit on the line at any one time.
The master manages the exchanges and only it can take the initiative.
It interrogates each of the slaves in succession.
No slave can send a message unless it is invited to do so.
In the event of an error during data exchange, the master repeats the question and declares the interrogated slave absent if no response is received within a given time period.
If a slave does not understand a message, it sends an exception response to the master.
The master may or may not repeat the request.
Slave i
Slave j
Slave k
Direct slave to slave communication is not possible.
For slave to slave communication, the master application software must be designed accordingly: to interrogate a slave and send back the data received to the other slave.
Two types of dialog are possible between master and slaves:
• The master sends a request to a slave and waits for it to respond.
• The master sends a request to all slaves without waiting for them to respond (broadcasting principle).
Addresses
• The Modbus addresses of the Lexium Controller can be configured from 1 to 247.
• Address 0 coded in a request sent by the master is reserved for broadcasting. The Lexium Controller takes account of the request but does not respond to it.
• The Lexium Controller has a Modbus server that has its own address:
- A Modbus server to enable the Lexium Controller to access all the parameters available in the Modbus table.
- The list of these parameters and variables (%MW…) used by the Motion Pro/CoDeSys software can be found in the document:
18
Modbus protocol
Modbus functions
The following table indicates which Modbus functions are managed by the Lexium Controller and specifies their limits.
The "read" and "write" functions are defined from the point of view of the master.
Code
3 = 16#03
6 = 16#06
8 = 16#08
16 = 16#10
43 = 16#2B
Modbus name
Read Holding Registers
Write Single Register
Diagnostics
Write Multiple Registers
Read Device Identification
Function name
Read N output words
Write one output word
Diagnostics
Write N output words
Identification
Broadcasting
NO
YES
NO
YES
NO
Max. value of N
121 words max.
–
121 words max.
–
Read N output words: function 3
Note: Hi = most significant bits, Lo = least significant bits.
This function can be used to read the Lexium Controller parameters, regardless of their type.
Maximum size of the number of variables that can be read in one frame: 121
Request
Slave no.
1 byte
03
1 byte
No. of first word
Hi Lo
2 bytes
Number of words
Hi Lo
2 bytes
Lo
CRC16
2 bytes
Hi
Response
Slave no.
1 byte
03
1 byte
Example 1: Using function 3 to read the 4 words %mW3102 (W3102) to %mW3105 (W3105) (16#0C1E to 16#0C21) in slave 2, where:
• %mw3102 V (W3102 = 16#0028)
• %mw3102 V (W3103 = 16#0258)
• %mw3104 V (W3104 = 16#01F4)
• %mw3105 V (W3105 = 16#0000)
Request
02 03 0C1E 0004 276C
Response
02 03
Value of:
08
Number of bytes read
1 byte
0028
W3 102
First word value
Hi Lo
2 bytes
0258
W3 103
-------
01F4
W3 104
Last word value
Hi Lo
2 bytes
0000
W3 105
52B0
Lo
CRC16
2 bytes
Hi
19
Modbus protocol
Write one output word: function 6
Request and response (the frame format is identical)
Slave no.
1 byte
06
1 byte
Hi
Word number
Lo
2 bytes
Hi
Value of word
Lo
2 bytes
Example: Writing value 16#000D to word %mw9001 (W9001) (16#2329) in slave 2 (value = 13).
Request and response:
02 06 2329 000D 9270
Lo
CRC16
2 bytes
Hi
Diagnostics: function 8
Subcode 16#00: echo
This function asks the slave being interrogated to echo (return) the message sent by the master in its entirety.
Request and response:
Slave no.
1 byte
08
1 byte
Hi
Sub-code
Lo
2 bytes
Hi
Data
N bytes
Lo Lo
CRC16
2 bytes
Hi
Sub-code
00
Request data
XX YY
Response data
XX YY
Example: Values 16#31 and 16#32 echoed by slave 4
Request and response (if function successful)
Slave no.
Request code or Response code
08
Hi
Sub-code
Lo
00 00 04
(hexadecimal values)
Echo
Value of 1st byte
31
Function executed
Value of 2nd byte
32
Lo
CRC16
Hi
74 1B
20
Modbus protocol
Write N output words: function 16 (16#10)
This function can be used to write the Lexium Controller parameters or variables, regardless of their type. The maximum size of the number of variables that can be read in one frame is 121.
Request
Slave no.
1 byte
10
1 byte
No. of first word
Hi Lo
2 bytes
Number of words Number of bytes
Hi Lo
2 bytes 1 byte
Value of first word
Hi Lo
2 bytes
-------
Lo
CRC16
Hi
2 bytes
Response
Slave no.
10
1 byte 1 byte
No. of first word
Hi Lo
2 bytes
Number of words
Hi Lo
2 bytes
Lo
CRC16
2 bytes
Hi
Example: Writing values 20 and 30 to words W9001 and W9002 in slave 2 (W9001 to 20 and W9002 to 30)
Request
Slave no.
02
Request code
10
No. of first word
Hi
23
Lo
29
Number of words
Hi Lo
00 02
Number of bytes
04
Value of first word Value of second word
Hi Lo Hi Lo
00 14 00 1E
CRC16
Lo
73
Hi
A4
Response
Slave no.
Response code
10
Hi
No. of first word
Lo
23 29
Number of words
Hi Lo
00 02
Lo
9B
CRC16
Hi
B7 02
(hexadecimal values)
21
Modbus protocol
Identification: function 43 (16#2B)
Request
Slave no.
1 byte
2B
1 byte
Type of MEI
0E
1 byte
ReadDeviceId
01
1 byte
Response
Slave no.
1 byte
2B
1 byte
Type of MEI
0E
1 byte
ReadDeviceId
01
1 byte
------Number of additional frames
00
1 byte
Object Id
00
1 byte
Lo
CRC16
2 bytes
Hi
Degree of conformity
02
1 byte
Next object Id
00
1 byte
-------
Number of objects
04
1 byte
-------
------------Id of object no. 1
00
1 byte
------Id of object no. 2
01
1 byte
------Id of object no. 3
02
1 byte
Length of object no. 1
0D
1 byte
Length of object no. 2
0B
1 byte
Length of object no. 3
04
1 byte
Value of object no. 1
“Telemecanique”
13 bytes
Value of object no. 2
“LMC20”
11 bytes
Value of object no. 3
“0201”
0 4 bytes
-------
-------
-------
Lo
1 byte
CRC16
Hi
1 byte
The total response size given in this example equals 55 bytes
The response contains the following three objects:
• Object no.
1:
• Object no.
2:
• Object no.
3:
Manufacturer name (always "Telemecanique", i.e., 13 bytes).
Device reference (ASCII string; for example: “LMC20”, i.e.,11 bytes).
The length of this object varies according to device type. Use the “Length of object no. 2” field to determine the length.
Device version, in "MMmm" format where "MM" represents the determinant and "mm" the subdeterminant
(4-byte ASCII string; for example: “0201” for version 2.1).
Negative response specifically related to the Identification function:
Slave no.
1 byte
2B + 80
AB
1 byte
Type of MEI
0E
1 byte
Error code
00 to 02
1 byte
Lo
1 byte
CRC16
Hi
1 byte
Error code:
16#00 =
16#01 =
16#02 =
No error
The question code (16#2B), the Type of MEI (16#0E) or the ReadDeviceId (16#01) contained in the question is incorrect.
The Object Id (16#00) contained in the question is incorrect.
22
Modbus protocol
Exception responses
An exception response is returned by a slave when it is unable to perform the request addressed to it.
Format of an exception response:
Slave no.
Response code Error code
CRC16
Lo Hi
1 byte 1 byte 1 byte 2 bytes
Response code: function code of the request + 16#80 (the most significant bit is set to 1).
Error code:
1 = The requested function is not recognized by the slave
2 = The word addresses indicated in the request do not exist in the slave
3 = The word values indicated in the request are not permissible in the slave
4 = The slave has started to execute the request but cannot continue to process it completely
Read non-existent or protected parameters
When a set of parameters is read or when a non-existent or protected parameter is written by a Modbus function, the Lexium Controller sends an exception response.
The list of parameters or variables that can be accessed by Modbus is as follows:
• From 0 to 59999, all the parameters are available.
• A large number of the parameters from 60000 upwards are not available and are used for Ethernet connectivity and functions.
• After the Ethernet parameters, the zone does not exist.
For a list of the available Ethernet parameters, refer to the Ethernet manual.
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