Vacon CX Series, CX211OPT, CXS Series, CXL Series User Manual

Modbus

Fieldbus

Option Board

USER’S MANUAL

Subject to changes without notice

VACON

CX/CXL/CXS

FREQUENCY CONVERTERS

F O R S M O O T H C O N T R O L

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INDEX

1. GENERAL............................................................................................................................................3

2. SPECIFICATIONS................................................................................................................................4

3. MODBUS.............................................................................................................................................5

3.1 General ...........................................................................................................................................5

3.2 Modbus frames ................................................................................................................................6

3.3 Modbus functions .............................................................................................................................6

3.4 Error detection .................................................................................................................................6

3.5 Exception responses ........................................................................................................................7

4. INSTALLATION ...................................................................................................................................8

5. CONNECTIONS.................................................................................................................................. 10

5.1 Board layout .................................................................................................................................. 10

5.2 Modbus connections ....................................................................................................................... 10

5.3 I/O-control connections ................................................................................................................... 11

6. COMMISSIONING.............................................................................................................................. 12

7. MODBUS-VACON CX INTERFACE...................................................................................................... 13

7.1 Modbus function codes ................................................................................................................... 13

7.1.1 Function code 1, Read Control Bits .......................................................................................... 13

7.1.2 Function code 2, Read Status Bits........................................................................................... 13

7.1.3 Function code 3, Read Parameters .......................................................................................... 13

7.1.4 Function code 4, Read Variables ............................................................................................. 14

7.1.5 Function code 5, Write Control Bits.......................................................................................... 14

7.1.6 Function code 6, Write Parameter............................................................................................ 14

7.1.7 Function code 8, Diagnostic.................................................................................................... 14

7.2 VACON control interface ................................................................................................................. 16

7.3 VACON parameters........................................................................................................................ 17

7.3.1 Frequency reference ............................................................................................................... 17

7.3.2 Monitoring variables ................................................................................................................ 17

7.3.3 Active Fault Code................................................................................................................... 18

7.3.4 Parameter Write and Read...................................................................................................... 19

7.4 CONNECTIONS (small Modbus Board for Vacon CXS, Vacon CX211OPT) ........................................... 20

7.4.1 Board layout .......................................................................................................................... 20

7.4.2 Modbus connections ............................................................................................................... 20

7.5 Installation of CX211OPT in Vacon CXS drives ................................................................................... 21

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1. GENERAL

Vacon frequency converters can be connected to the Modbus by using the fieldbus board. The converter
can then be controlled, monitored and programmed from the Host system.

The used I/O can be also extended with the Fieldbus board:

• 4 digital inputs (standard signals)

• 4 digital outputs (standard signals)

• Thermistor input (can be directly connected to the motor thermistors for overtemperature trip)

• Encoder input

The Fieldbus board can be installed into the already existing place of the option board inside the frequency
converter.

The control connections are isolated from the mains potential and I/O ground is connected to the frame of
the device via a 1 MΩ resistor and 4.7 nF capacitor*. The control I/O ground can be connected also
directly to the frame by changing the position of the jumper X9 (GND ON/OFF) to ON-position. Digital
inputs and digital outputs are also isolated from the I/O ground.

NOTE !

Internal components and circuit boards (except for the isolated I/O terminals) are at mains
potential when the frequency converter is connected to the mains. This voltage is extremely
dangerous and may cause death or severe injury if you come in contact with it.

The control I/O terminals are isolated from the mains potential, but the I/Os (if jumper X9 is in
OFF position) may have dangerous voltage connected even if the power is off on the frequency
converter.

* Default value (X9 is GND OFF- position)

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2. SPECIFICATIONS

Modbus - Interface 9-pin DSUB connector (female)
connections Transfer method RS-485, Half duplex

Transfer cable Twisted pair (1 pair and shield)
Electrical isolation 500 V DC

I/O -control Digital input (4 pcs) 24 V: “0” ≤10 V, “1” ≥18 V, Ri = 5 kΩ
connections Digital output (4 pcs) Open collector output, 50 mA/48 V

Termistor input (1 pcs) R

trip

= 4.7 kΩ

Encoder input (3 pcs) 24 V: “0” ≤10 V, “1” ≥18 V, Ri = 3.3 kΩ

5 V : “0” ≤2 V, “1” ≥3 V, Ri = 330 Ω

Aux. voltage 24 V (±20%), max 50 mA

Safety Fulfills EN50178 standard

Table 2-1. Specifications

Communication mode RTU
Function codes 1

2
3
4
5
6
8

Broadcast (codes 5,6)

Read Digital Output
Read Digital Input
Read Holding Register
Read Input Register
Write Single Digital Output
Write Single Register
Diagnostic

Communication parameters

- Address

- Parity

- Stop Bits

- Baud Rate

1 to 247

None, Odd or Even

1

300 to 19200 Baud

Table 2-2. Modbus communication data

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3. MODBUS

3.1 General

The MODBUS protocol is an industrial communications and distributed control system to integrate PLCs,
computers, terminals, and other monitoring, sensing, and control devices. MODBUS is a Master-Slave
communications protocol. The Master controls all serial activity by selectively polling one or more slave
devices. The protocol provides for one master device and up to 247 slave devices on a common line.
Each device is assigned an address to distinguish it from all other connected devices.

The MODBUS protocol uses the master-slave technique, in which only one device (the master) can initiate
a transaction. The other devices (the slaves) respond by supplying the request data to the master, or by
taking the action requested in the query. The master can address individual slaves or initiate a broadcast
message to all slaves. Slaves return a message (‘response’) to queries that are addressed to them
individually. Responses are not returned to broadcast queries from the master.

A transaction comprises a single query and single response frame or a single broadcast frame. The
transaction frames are defined below.

Query message from master

Device address Device address

Function code Function code

Eight-Bit Eight-Bit

Data Bytes Data Bytes

Error Check Error Check

Response message from slave

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3.2 Modbus frames

Two modes of transmission are available for use in a MODBUS system. The modes are ASCII (American
Standard Code for Information Interchange), and RTU, (Remote Terminal Unit.). The Fieldbus board uses

only RTU mode.

The format for each byte in RTU mode:
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)
In RTU mode, messages start and end with a silent 3.5 characters times (T1-T2-T3-T4). The entire

message frame must be transmitted as a continuous stream. A typical message frame is shown below.

Start Address Function Data CRC Check End
T1-T2-T3-T4 8 bits 8 bits n*8bits 16 bits T1-T2-T3-T4

The individual slave devices are assigned addresses in the range of 1 - 247. Address 0 is used for the
broadcast address, which all slave devices recognize.

3.3 Modbus functions

The Function Code field tells the addressed slave what function to perform. The following table lists those
functions supported by the Fieldbus board:

Code Name Meaning of Fieldbus board

01 READ COIL STATUS Read Control bits
02 READ INPUT STATUS Read Status bits
03 READ HOLDING REGISTER Read VACON parameter
04 READ INPUT REGISTER Read VACON variable
05 FORCE SINGLE COIL Write Control bits
06 PRESET SINGLE REGISTER Write VACON parameter
08 DIAGNOSTICS Test and checking of the communication system

3.4 Error detection

Communications errors usually consist of a changed bit or bits within a message. Communications errors
are detected by character framing, a parity check, and a redundancy check.

The MODBUS system provides several levels of error checking to assure the quality of the data
transmission. To detect multibit errors where the parity has not changed, the system uses redundancy
checks: Cyclical Redundancy Check, (CRC), for the RTU mode and Longitudinal Redundancy Check,
(LRC), for the ASCII mode. The Fieldbus board uses only RTU mode.

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3.5 Exception responses

If the slave receives the query without a communication error, but cannot handle it, the slave will return an
exception response informing the master of the nature of the error. The exception response codes are
listed below.

Code Name Description
01 ILLEGAL FUNCTION The message function requested is not recognized by the

slave.

02 ILLEGAL DATA ADDRESS The received data address is not an allowable address for

the slave.

03 ILLEGAL DATA VALUE The received data value is not an allowable value for the

slave.

04 SLAVE DEVICE ERROR An unrecoverable error occurred while the slave was

attempting to perform the requested action,

06 SLAVE DEVICE BUSY The message was received without error, but the slave was

engaged in processing a long duration program command

In an exception response, the slave sets a most-significant bit (MSB) of the function code to 1. The slave
returns an exception code in the data field.

Example:
Query:

01 01 04 2E 00 01 CRC16

Slave
address

Function Starting

address HI

Starting
address LO

Number of
bits HI

Number of
bits LO

2 bytes

Exception Response:

01 81 02 CRC16

Slave
address

Function Response

code

2 bytes