Leroy-Somer PX-MODBUS User manual

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4071 en - 03.2007 / a
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PX-MODBUS
Communication module for
POWERDRIVE, PROXIDRIVE, VARMECA 33/34
Installation

2
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
NOTE
LEROY-SOMER reserves the right to modify the characteristics of its products at any time in
order to incorporate the latest technological developments. The information contained in this
document may therefore be changed without notice.
CAUTION
For the user's own safety, this variable speed drive must be connected to an approved earth
( terminal).
If accidentally starting the installation is likely to cause a risk to personnel or the machines
being driven, it is essential to supply the equipment via an isolating switch and a
circuit-breaking device (power contactor) which can be controlled via an external safety
system (emergency stop, detection of errors on the installation).
The variable speed drive is fitted with safety devices which, in the event of a fault, control
stopping and thus stop the motor. The motor itself can become jammed for mechanical
reasons. Voltage fluctuations, and in particular power cuts, may also cause the motor to stop.
The removal of the causes of the shutdown can lead to restarting, which may be dangerous
for certain machines or installations.
In such cases, it is essential that the user takes appropriate precautions against the motor
restarting after an unscheduled stop.
The variable speed drive is designed to be able to supply a motor and the driven machine
above its rated speed.
If the motor or the machine are not mechanically designed to withstand such speeds, the user
may be exposed to serious danger resulting from their mechanical deterioration.
Before programming a high speed, it is important that the user checks that the installation can
withstand it.
The variable speed drive which is the subject of this manual is designed to be integrated in an
installation or an electrical machine, and can under no circumstances be considered to be a
safety device. It is therefore the responsibility of the machine manufacturer, the designer of the
installation or the user to take all necessary precautions to ensure that the system complies
with current standards, and to provide any devices required to ensure the safety of equipment
and personnel.
Using the drive for hoisting: when using this application, it is essential to follow the special
instructions in an application-specific manual which is available on request. It is the
responsibility of the user to obtain this manual from his usual LEROY-SOMER contact.
LEROY-SOMER declines all responsibility in the event of the above recommendations not
being observed.
........................................

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
3
SAFETY AND OPERATING INSTRUCTIONS FOR VARIABLE SPEED DRIVES
(in accordance with the low voltage directive 73/23/EEC modified by 93/68/EEC)
• Throughout the manual, this
symbol warns of consequences
which may arise from inappropriate use
of the drive, since electrical risks may
lead to material or physical damage as
well as constituting a fire hazard.
1 - General
Depending on their degree of protection,
the variable speed drives may contain
unprotected live parts, which may be
moving or rotating, as well as hot surfaces,
during operation.
Unjustified removal of protection devices,
incorrect use, faulty installation or
inappropriate operation could represent a
serious risk to personnel and equipment.
For further information, consult the manual.
All work relating to transportation,
installation, commissioning and
maintenance must be performed by
experienced, qualified personnel (see
IEC 364 or CENELEC HD 384, or DIN VDE
0100 and national specifications for
installation and accident prevention).
In these basic safety instructions, qualified
personnel means persons competent to
install, mount, commission and operate the
product and possessing the relevant
qualifications.
2 - Use
Variable speed drives are components
designed for integration in installations or
electrical machines.
When integrated in a machine,
commissioning must not take place until it
has been verified that the machine
conforms with directive 89/392/EEC
(Machinery Directive). It is also necessary
to comply with standard EN 60204, which
stipulates in particular that electrical
actuators (which include variable speed
drives) cannot be considered as
circuit-breaking devices and certainly not
as isolating switches.
Commissioning can take place only if the
requirements of the Electromagnetic
Compatibility Directive (89/336/EEC,
modified by 92/31/EEC) are met.
The variable speed drives meet the
requirements of the Low Voltage Directive
73/23/EEC, modified by 93/68/EEC. The
harmonised standards of the
DIN VDE 0160 series in connection with
standard VDE 0660, part 500 and EN
60146/VDE 0558 are also applicable.
The technical characteristics and
instructions concerning the connection
conditions specified on the nameplate and
in the documentation provided must be
observed without fail.
3 - Transportation, storage
All instructions concerning transportation,
storage and correct handling must be
observed.
The climatic conditions specified in the
technical manual must be observed.

4
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
4 - Installation
The installation and cooling of equipment
must comply with the specifications in the
manual supplied with the product.
The variable speed drives must be
protected against any excessive stress. In
particular, there must be no damage to
parts and/or modification of the clearance
between components during transportation
and handling. Avoid touching the electronic
components and contact parts.
The variable speed drives contain parts
which are sensitive to electrostatic stresses
and may be easily damaged if handled
incorrectly. Electrical components must not
be exposed to mechanical damage or
destruction (risks to health!).
5 - Electrical connection
When work is performed on variable speed
drives which are powered up, the national
accident prevention regulations must be
observed.
The electrical installation must comply with
the relevant specifications (for example
conductor cross-sections, protection via
fused circuit-breaker, connection of
protective conductor). More detailed
information is given in the manual.
Instructions for an installation which meets
the requirements for electromagnetic
compatibility, such as screening, earthing,
presence of filters and correct insertion of
cables and conductors, are given in the
documentation supplied with the variable
speed drives. These instructions must be
followed in all cases, even if the variable
speed drive carries the CE mark.
Adherence to the limits given in the EMC
legislation is the responsibility of the
manufacturer of the installation or the
machine.
6 - Operation
Installations in which variable speed drives
are integrated must be fitted with additional
protection and monitoring devices as laid
down in the current relevant safety
regulations, such as the law on technical
equipment, accident prevention
regulations, etc. Modifications to the
variable speed drives using control
software are permitted.
Active parts of the device and the live
power connections must not be touched
immediately after the variable speed drive
is powered down, as the capacitors may
still be charged. In view of this, the
warnings fixed to the variable speed drives
must be observed.
During operation, all doors and protective
covers must be kept closed.
7 - Servicing and maintenance
Refer to the manufacturer's documentation.
This manual is to be given to the end
user.

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
5
CONTENTS
1 - GENERAL INFORMATION................................................................................ 7
1.1 - General information ......................................................................................... 7
1.2 - Dimensions...................................................................................................... 7
2 - INSTALLATION ................................................................................................. 8
2.1 - Mounting position on POWERDRIVE drive ..................................................... 8
2.2 - Mounting position on PROXIDRIVE drive........................................................ 8
2.3 - Mounting position on VARMECA 33/34 drive .................................................. 8
3 - ELECTRICAL CONNECTIONS ......................................................................... 9
4 - SETTING THE COMMUNICATION PARAMETERS........................................ 10
5 - MODBUS RTU OPERATION ........................................................................... 12
5.1 - General information ....................................................................................... 12
5.2 - Description of exchanges............................................................................... 12
5.3 - Parameter assignment................................................................................... 13
5.4 - Data encoding................................................................................................ 13
5.5 - Control word and status word ........................................................................ 13
5.6 - Function codes............................................................................................... 14
5.7 - Example......................................................................................................... 17
5.8 - Wait time........................................................................................................ 17
5.9 - Exceptions ..................................................................................................... 17
5.10 - CRC ............................................................................................................. 18

6
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
Notes

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
7
1 - GENERAL INFORMATION
1.1 - General
PX-Modbus is a Modbus RTU option
designed for Powerdrive, Proxidrive and
Varmeca 33/34 drives.
As standard, these drives incorporate a
Modbus RTU serial link port, type RS485
2-wire, non-isolated, accessible via the
RJ45 connector. When the user wishes to
keep the keypad (KEYPAD-LCD)
permanently connected, or if he requires an
isolated link, the Modbus RTU option with
2 or 4-wire isolated RS485 serial link port
should be added.
Colour of the option label: blue.
1.2 - Dimensions
The PX-Modbus module can be
incorporated in POWERDRIVE,
PROXIDRIVE and VARMECA 33/34
drives, and does not alter the drive
dimensions.

8
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
2 - INSTALLATION
• Always switch off the drive before connecting/disconnecting the option to/from
the drive. Check that the D.C. bus has fully discharged (this takes over a minute
on Powerdrives).
2.1 - Mounting position on POWERDRIVE drive
Offer the module to the special connector slot, push gently until you hear a "click" as it locks
in place.
2.2 - Mounting position on
PROXIDRIVE drive
Offer the module to the special connector
slot, push gently until you hear a "click" as
it locks in place.
2.3 - Mounting position on
VARMECA 33/34 drive
Offer the module to the special connector
slot, push gently until you hear a "click" as
it locks in place.
PX-Modbus
module
position
PX-Modbus
module
position
PX-Modbus
module
position

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
9
3 - ELECTRICAL CONNECTIONS
WARNING:
Always switch off the drive before connecting/disconnecting the option to/from the drive.
Check that the D.C. bus has fully discharged (this takes over a minute on Powerdrives).
9-pin female SUB-D
Pin Description
1
2
3
4
5
6
7
8
9
Shielding: 0V "com"
0V "com"
TX\
RX\
not connected
not connected
TX
RX
not connected
not connected
5-pin screw terminal block
Pin Description
1
2
3
4
5
0V "com"
RX\
RX
TX\
TX
12345
51
96

10
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
4 - SETTING THE COMMUNICATION
PARAMETERS
From version v2.20 of Powerdrive and
version v3.00 of Proxidrive and Varmeca
33/34, the PX-Modbus card parameters
are set from menu 15.
Note: Modbus configuration of the RJ45 is
still in menu 11. On subsequent versions,
Modbus configuration of the RJ45 is
completely independent from Modbus
configuration of the PX-Modbus module.
On older software versions, menu 11
configures both Modbus modules (no menu
15 in this case).
: Option code
Value 352 for Modbus.
: PX-Modbus address
Adjustment range :0 to 247
Factory setting :1
Used to define the drive address in the
case of control or monitoring via the serial
link in Modbus RTU. Avoid values including
a zero since these are used for addressing
groups of drives. This parameter is the
equivalent of 11.23 for the RJ45.
: Modbus speed
Adjustment range :300 (0) to 115200 (9)
Factory setting :19200 (6)
Used to select the data transfer speed in
Modbus RTU.
*: These speeds are non-operational on the
PROXIDRIVE and VARMECA 33/34.
This parameter is the equivalent of 11.25
for the RJ45.
: Parity, number of stop bits
Adjustment range :NONE, 2STOP (0);
NONE, 1STOP (1);
EVEN, 1STOP (2);
ODD, 1STOP (3)
Factory setting :NONE, 2STOP (0)
NONE, 2STOP (0): no parity,
2 stop bits.
NONE, 1STOP (1): no parity,
1 stop bit.
EVEN, 1STOP (2): even parity,
1 stop bit.
ODD, 1STOP (3): odd parity,
1 stop bit.
This parameter is the equivalent of 11.27
for the RJ45.
15.01
15.03
Speed (Bauds) 15.04
300 0
600 1
1200 2
2400 3
4800 4
9600 5
19200 6
38400* 7
57600* 8
115200* 9
15.04
15.05

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
11
: Minimum comms transmit
delay
Adjustment range :0 to 250 ms
Factory setting :10 ms
The adjustment step is 2 ms.
Used to insert a time between data
reception and feedback. The delay
between a request from the master and the
response from the slave drive is at least 1.5
ms.
This parameter is the equivalent of 11.26
for the RJ45.
: Modbus timeout
Adjustment range :0.0 to 25 s
Factory setting :0 s
This parameter is used to generate a
"fieldbus" fault if no data has travelled on
Modbus in the time period set by this
parameter. It can thus be used to detect a
problem on the Modbus network.
The value 0 disables Modbus monitoring.
This parameter is the equivalent of 11.63
for the RJ45.
15.06
Request from the Master
Minimum comms transmit delay
Drive response
15.06
15.07

12
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
5 - MODBUS RTU OPERATION
5.1 - General
The MODBUS RTU protocol is a
master-slave type protocol (a single master
per network).
5.2 - Description of exchanges
Exchanges are initiated by the master,
which sends its request: if the slave
concerned has understood it, it sends its
response. Each frame (question or
response) contains four types of
information:
- The address of the slave concerned which
receives the question frame (request from
the master) or the address of the slave
which sends the response frame (encoded
in one byte)
- The function code which selects a
command (read or write words, bits, etc.)
for the question and response frames
(encoded in one byte)
- The data field containing the parameters
relating to the command (encoded in "n"
bytes)
- The CRC for the frame, calculated in
sixteen bits, which is used to detect
transmission errors
The frame is terminated with a minimum
silence period, equivalent to the
transmission time for 3.5 characters (e.g. at
19200 baud, the silence period must be at
least 1/19200 x 11 bits x 3.5, i.e. 2 ms). This
silence period indicates the end of the
message, and the slave can start to
process the transmitted data.
All requests from the master will result in a response from a single slave. The slave will
respond within the maximum permitted time (the minimum response time will never be less
than the silence period).
Description Characteristics
Normal physical
layer for multi-drop
operation
2-wire RS485
Bit stream Standard UART
asynchronous
symbols with
Non-Return to Zero
(NRZ)
Symbol Each symbol
consists of:
1 start bit
8 data bits (least
significant bit
transmitted first)
1 or 2 stop bits
according to 15.05
Baud rate 300, 600, 1200,
2400, 4800, 9600,
19200, 38400,
57600, 115200
baud
Address
slave Code Function Message
data CRC
16-bit Interval Silence
Master request Master request
Frame detection Frame processing
by the slave
Minimum silence period
Slave response
time
Slave response
Minimum silence period

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
13
5.3 - Parameter assignment
POWERDRIVE, PROXIDRIVE and
VARMECA 33/34 drives are configured
using a menu.parameter notation.
The "menu" and "parameter" indices can
take the values 0 to 99. Menu.parameter is
assigned to a MODBUS RTU register
menu x 100 + parameter.
In order to assign the parameters
correctly, the slave increments (+1) the
address of the received register.
Example: X = menu; Y = parameter
5.4 - Data encoding
MODBUS RTU uses a "big-endian"
representation for the addresses and data
items (except for the CRC which is
"little-endian"). This means that, when a
numerical quantity "bigger" than one byte is
transmitted, the most significant byte is
sent first.
For example:
5.5 - Control word and status word
Drive control commands can be managed
using a single parameter 6.42, called the
"control word".
This is because the value of 6.42
corresponds to a word in which each bit is
associated with a command. The
command is enabled when the bit is at 1,
and disabled when the bit is at 0.
To enable commands using the control
word, set 6.43 = 1 (control commands via
the terminals are no longer active), when
the drive is disabled.
Parameter 10.40, called the status word,
is used to group together data on the drive.
The value of 10.40 corresponds to a 15-bit
word, and each bit is associated with a
drive status parameter.
6.42: Control word
Drive parameter Register address
(protocol level)
X.Y (X x 100) + (Y – 1)
Examples:
1.02 101
1.00 99
0.01 0
12.33 1232
1st 2nd …
16 – bits 0x1234 would be: 0x12 0x34
Bits of
control
word
6.42
Corresponding
parameters Functions
06.15 Drive unlocking
16.30 Run forward
26.31 Jog
36.32 Run reverse
46.33 Forward/
56.34 Run
6-Reserved
7-Reserved
81.42 Analog
reference/
preset
reference
9-Reserved
10 - Reserved
11 - Reserved
12 - Reserved
13 10.33 Drive reset/
Reset
14 - Reserved

14
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
10.40: Status word
(1) Parameter not used on PROXIDRIVE
and VARMECA 33/34.
5.6 - Function codes
The function code determines the context
and data format of the message.
• Function code 3: Read multiple
Reading of a contiguous register or word
area. The slave sets an upper limit on the
number of registers or words that can be
read. If the limit is exceeded, the slave does
not respond.
Note: 20 drive parameters maximum can
be read.
Frame sent by the Master:
Frame returned by the slave:
Where n = 3 + number of bytes to be read.
Bitsof
status
word
10.40
Corresponding
parameters Drive status
010.01 Drive healthy
110.02 Drive active
210.03 Zero speed
310.04 Running at or
410.05 Below set speed
510.06 At speed
610.07 Above set speed
710.08 Load reached
810.09 Drive output is at
current limit
910.10 Dynamic braking
10 10.11 Braking IGBT
active
11 10.12 Braking resistor,
overload alarm
12 10.13 Direction
commanded
13 10.14 Direction running
14 10.15 (1) Mains loss
Function code Description
Decimal Hexadecimal
303 Read multiple
16-bit registers or
words
606 Write single 16-bit
register or word
16 10 Write multiple
16-bit registers or
words
23 17 Read and write
multiple 16-bit
registers or words
Bytes Description
0Slave address (1 to 247)
1Function code 0x03
2Start word or register address
MS byte
3Start word or register address
LS byte
4Number of words or registers to
be read MS byte
5Number of words or registers to
be read LS byte
6CRC LS byte
7CRC MS byte
Bytes Description
0Slave address
1Function code 0x03
2Number of bytes to be read
3Word or register 0 MS byte
4Word or register 0 LS byte
5Word or register 1 MS byte
6Word or register 1 LS byte
... …
nCRC LS byte
n + 1 CRC MS byte
slave n
Command (03)
Start word address
Number of words
CRC
1
hexadecimal byte
2
hexadecimal bytes
CRC
slave n
Command (03)
No. of bytes
Word number 0
Word number 1
…
1
hexadecimal byte
2
hexadecimal bytes

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
15
• Function code 6: Write single register
or word
Writing of a value to a single 16-bit register
or word. The normal response is an "echo"
of the request, after the register or word has
been written to.
Frame sent by the Master:
Frame sent by the slave:
• Function code 16: Write multiple
Writing of a contiguous register or word
area. The slave sets an upper limit on the
number of registers or words that can be
written. If the limit is exceeded, the slave
does not respond.
Note: 12 drive parameters maximum can
be written.
Frame sent by the Master:
Where n = 7 + number of bytes to be
written.
Bytes Description
0Slave address (0 to 247)
1Function code 0x06
2Word or register address MS
byte
3Word or register address LS byte
4Word or register value MS byte
5Word or register value LS byte
6CRC LS byte
7CRC MS byte
Bytes Description
0Slave address
1Function code 0x06
2Word or register address MS
byte
3Word or register address LS byte
4Word or register value MS byte
5Word or register value LS byte
6CRC LS byte
7CRC MS byte
CRC
slave n
Command (06)
Word address
Word value
1
hexadecimal byte
2
hexadecimal bytes
Bytes Description
0Slave address (1 to 247)
1Function code 0x10
2Start word or register address
MS byte
3Start word or register address
LS byte
4Number of words or registers to
be written MS byte
5Number of words or registers to
be written LS byte
6Number of bytes to be written
7Word or register 0 to be written
MS byte
8Word or register 0 to be written
LS byte
9Word or register 1 to be written
MS byte
10 Word or register 1 to be written
LS byte
... …
nCRC LS byte
n + 1 CRC MS byte
Start word address
Number of words
CRC
Nbs octets
Word number 0
Word number 1
…
slave n
Command (10h)
1 hexadecimal
byte
1
hexadecimal
byte 2
hexadecimal bytes
2
hexadecimal bytes

16
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
Frame returned by the slave:
• Function code 23: Read/write
Writing and reading of two contiguous
register or word areas. The slave sets an
upper limit on the number of registers or
words that can be written. If the limit is
exceeded, the slave does not respond.
Note: 20 drive parameters maximum can
be read and 10 drive parameters maximum
can be written.
Frame sent by the Master:
Where n = 11 + number of bytes to be
written.
Frame returned by the slave:
Where n = 3 + number of bytes to be read.
Bytes Description
0Slave address (1 to 247)
1Function code 0x10
2Start word or register address
MS byte
3Start word or register address
LS byte
4Number of words or registers
written MS byte
5Number of words or registers
written LS byte
6CRC LS byte
7CRC MS byte
slave n
Start word address
Number of words
CRC
1
hexadecimal byte
2
hexadecimal bytes
Command (10h)
Bytes Description
0Slave address (1 to 247)
1Function code 0x17
2Start word or register address to
be read MS byte
3Start word or register address to
be read LS byte
4Number of words or registers to
be read MS byte
5Number of words or registers to
be read LS byte
6Start word or register address to
be written MS byte
7Start word or register address to
be written LS byte
8Number of words or registers to
be written MS byte
9Number of words or registers to
be written LS byte
10 Number of bytes to be written
11 Word or register 0 MS byte
12 Word or register 0 LS byte
13 Word or register 1 MS byte
14 Word or register 1 LS byte
... …
nCRC LS byte
n + 1 CRC MS byte
Bytes Description
0Slave address (1 to 247)
1Function code 0x17
2Number of bytes to be read
3Word or register 0 MS byte
4Word or register 0 LS byte
5Word or register 1 MS byte
6Word or register 1 LS byte
... …
nCRC LS byte
n + 1 CRC MS byte

INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
17
5.7 - Example
Drive address = 1 (Default address).
Reading of 3 drive parameters from 1.05.
1.05 becomes 1.04 which is equal to 68 in hexadecimal (Modbus address = parameter
address - 1).
• Request
• Response
5.8 - Wait time
In MODBUS RTU, when the master sends
a message to a slave, it sets a wait time
between the end of its request and the start
of the response from the slave, which
makes it possible to detect any missing
response.
5.9 - Exceptions
If the message is incorrect and the frame is
not received, or if the CRC is faulty, then
the slave will not produce an exception, and
in this case the master will not obtain a
response from the slave ("timeout"). If a
write request (function code 16 or 23)
exceeds the maximum size accepted by
the slave, then the slave will reject the
message. No exception will be transmitted
and the master will not obtain a response.
Example (hex) RTU (binary)
Slave address 10000 0001
Function 03 0000 0011
Start word or register address (MS byte) 00 0000 0000
Start word or register address (LS byte) 68 0110 1000
Number of words or registers (MS byte) 00 0000 0000
Number of words or registers (LS byte) 03 0000 0011
CRC check: LS byte 84 1000 0100
MS byte 17 0001 0111
Total bytes: 8
Example (hex) RTU (binary)
Slave address 10000 0001
Function 03 0000 0011
Number of bytes 06 0000 0110
Word or register 0 (MS byte) 00 0000 0000
Word or register 0 (LS byte) 2D 0010 1101
Word or register 1 (MS byte) 05 0000 0101
Word or register 1 (LS byte) DC 1101 1100
Word or register 2 (MS byte) 00 0000 0000
Word or register 2 (LS byte) 00 0000 0000
CRC check: LS byte 4C 0100 1100
MS byte 45 0100 0101
Total bytes: 11

18
INSTALLATION
PX-MODBUS
Communication module for POWERDRIVE, PROXIDRIVE, VARMECA 33/34
4071 en - 03.2007 / a
LEROY-SOMER
5.10 - CRC
This control word is used to detect
transmission errors. It is calculated in
16 bits from all the bytes of the question
and response frames.
Algorithm:
START
CRC = 0xFFFF
Number of bytes processed = 0
Next byte = first byte
REPEAT
{Byte to be processed = next byte;
CRC = CRC XOR byte to be
processed
REPEAT eight times
{IF (CRC odd) then
CRC = CRC/2 XOR
0xA001
elseCRC = CRC/2
}
Number of bytes processed =
Number of bytes processed + 1
}
WHILE(Number of bytes processed ≤
Number of bytes to be
processed)
END.

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