Lenze AC Tech POSITIONSERVO User manual

Modbus Communication Module
Communications Interface Reference Guide
P94MOD01B

2P94MOD01B
Copyright ©2005 by AC Technology Corporation.
All rights reserved. No part of this manual may be reproduced or transmitted in any form without written
permission from AC Technology Corporation. The information and technical data in this manual are subject to
change without notice. AC Tech makes no warranty of any kind with respect to this material, including, but not
limited to, the implied warranties of its merchantability and fitness for a given purpose. AC Tech assumes no
responsibility for any errors that may appear in this manual and makes no commitment to update or to keep
current the information in this manual.
MotionView®, PositionServo®, and all related indicia are either registered trademarks or trademarks of Lenze
AG in the United States and other countries.
ModBus®is a registered trademark of ‘Schneider Automation’.
This document printed in the United States of America
About These Instructions
This documentation applies to Modbus RTU and Modbus TCP/IP communications for the PositionServo drive and
should be used in conjunction with the PositionServo User Manual (S94P01) that shipped with the drive. These
documents should be read carefully as they contain important technical data and describe the installation and
operation of the drive and this option module.

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Table of Contents
1. Safety Information...................................................................................................4
1.1 Warnings, Cautions & Notes.............................................................................................4
1.2 Reference Documents...................................................................................................... 6
2. Introduction.............................................................................................................6
2.1 Modbus Overview ........................................................................................................... 6
2.2 Ethernet TCP/IP Modbus Configuration............................................................................ 6
2.3 Modbus RTU Implementation Specification ..................................................................... 7
3. Installation ..............................................................................................................9
3.1 Mechanical Installation .................................................................................................... 9
3.2 Electrical Installation....................................................................................................... 10
4 Modbus Protocol Details.........................................................................................11
4.1 Data Transmission.......................................................................................................... 11
4.2 Register Numbering........................................................................................................ 12
4.3 Supported Modbus Function Codes................................................................................. 12
5 Drive Memory Access ............................................................................................12
5.1 Mapping from Drive Variable to the Register Address...................................................... 12
5.2 Register Reading ............................................................................................................ 13
5.3 Register Writing .............................................................................................................. 13
5.4 No Response Conditions ................................................................................................. 14
5.5 Exception Responses ...................................................................................................... 15
6 Commissioning ......................................................................................................16
6.1 Drive Monitoring ............................................................................................................. 16
6.2 Controlling the Drive .......................................................................................................16
6.3 Changing Drive Parameters ............................................................................................ 16
7 Programming Parameters ......................................................................................16
7.1 Negative Number Transmission ...................................................................................... 16

4P94MOD01B
1. Safety Information
1.1 Warnings, Cautions & Notes
General
Some parts of Lenze controllers (frequency inverters, servo inverters, DC controllers) can be live, with the
potential to cause attached motors to move or rotate. Some surfaces can be hot.
Non-authorized removal of the required cover, inappropriate use, and incorrect installation or operation creates
the risk of severe injury to personnel or damage to equipment.
All operations concerning transport, installation, and commissioning as well as maintenance must be carried
out by qualified, skilled personnel (IEC 364 and CENELEC HD 384 or DIN VDE 0100 and IEC report 664 or DIN
VDE0110 and national regulations for the prevention of accidents must be observed).
According to this basic safety information, qualified skilled personnel are persons who are familiar with the
installation, assembly, commissioning, and operation of the product and who have the qualifications necessary
for their occupation.
Application as directed
Drive controllers are components which are designed for installation in electrical systems or machinery. They
are not to be used as appliances. They are intended exclusively for professional and commercial purposes
according to EN 61000-3-2. The documentation includes information on compliance with the EN 61000-3-2.
When installing the drive controllers in machines, commissioning (i.e. the starting of operation as directed)
is prohibited until it is proven that the machine complies with the regulations of the EC Directive 98/37/EC
(Machinery Directive); EN 60204 must be observed.
Commissioning (i.e. starting of operation as directed) is only allowed when there is compliance with the EMC
Directive (89/336/EEC).
The drive controllers meet the requirements of the Low Voltage Directive 73/23/EEC. The harmonised standards
of the series EN 50178/DIN VDE 0160 apply to the controllers.
The availability of controllers is restricted according to EN 61800-3. These products can cause radio
interference in residential areas.
Installation
Ensure proper handling and avoid excessive mechanical stress. Do not bend any components and do not
change any insulation distances during transport or handling. Do not touch any electronic components and
contacts.
Controllers contain electrostatically sensitive components, which can easily be damaged by inappropriate
handling. Do not damage or destroy any electrical components since this might endanger your health!
Electrical connection
When working on live drive controllers, applicable national regulations for the prevention of accidents (e.g. VBG
4) must be observed.
The electrical installation must be carried out according to the appropriate regulations (e.g. cable cross-sections,
fuses, PE connection). Additional information can be obtained from the national regulation documentation. In
the United States, electrical installation is regulated by the National Electric Code (nec) and NFPA 70 along with
state and local regulations.

5 P94MOD01B
The documentation contains information about installation in compliance with EMC (shielding, grounding, filters
and cables). These notes must also be observed for CE-marked controllers.
The manufacturer of the system or machine is responsible for compliance with the required limit values
demanded by EMC legislation.
Operation
Systems including controllers must be equipped with additional monitoring and protection devices according to
the corresponding standards (e.g. technical equipment, regulations for prevention of accidents, etc.). You are
allowed to adapt the controller to your application as described in the documentation.
DANGER!
• After the controller has been disconnected from the supply
voltage, live components and power connection must not be touched
immediately, since capacitors could be charged. Wait at least 60
seconds before servic-ing the drive Please observe the corresponding
notes on the controller.
• Do not continuously cycle input power to the controller more than once
every three minutes.
• Please close all protective covers and doors during operation.
WARNING!
Network control permits automatic operation of the inverter drive.
The system design must incorporate adequate protection to prevent
personnel from accessing moving equipment while power is applied to
the drive system.
Pictographs used in these instructions:
Pictograph Signal Word Meaning Consequence if Ignored
DANGER! Warning of Hazardous Electrical
Voltage.
Reference to an imminent
danger that may result in death
or serious personal injury if the
corresponding measures are
not taken.
WARNING! Impending or possible danger to
personnel
Death or injury
STOP! Possible damage to equipment Damage to drive system or its
surroundings
NOTE Useful tip: If note is observed, it
will make using the drive easier

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1.2 Reference Documents
• Modbus Application Protocol Specification V1.1
To view this specification, visit: http://www.modbus.org/tech.php
or: http://www.modbus-ida.org/specs.php
• Modbus Over Serial Line Specification & Implementation Guide V1.0.
Refer to: http://www.modbus.org/
• PositionServo Programming Manual: PM94P01
Refer to: http://www.actech.com
NOTE:
The complete list of variables can be found in Appendix A of the PositionServo
Programming Manual (PM94P01).
2. Introduction
This reference guide assumes that the reader has a working knowledge of Modbus RTU or Modbus TCP/IP
Protocol and familiarity with the programming and operation of motion control equipment. This guide is intended
as a reference only. The PositionServo drive supports both Modbus TCP/IP and Modbus RTU communication
protocols. Modbus TCP/IP communications can be established via the PositionServo drive’s Ethernet port.
When using the RS485 option module (P/N E94ZARS41), Modbus RTU is the standard communication protocol.
Refer to Section 3 for installation of the RS485 option module.
2.1 Modbus Overview
Modbus is an internationally accepted asynchronous serial protocol designed for commercial and industrial
automation applications. The Modbus RTU architecture is based upon a Master-Slave orientation. In Modbus
RTU, the PositionServo drive always acts as the slave, responding to reads and writes from the Master. In
Modbus TCP/IP, the PositionServo drive can act as the Master or a slave. While the Modbus RTU protocol does
not specify the physical layer, the E94ZARS41 module uses a 2-wire RS-485 physical interface which is quite
common and well suited for the industrial environment. The E94ZARS41 module provides both galvanic and
optical isolation of the physical interface.
2.2 Ethernet TCP/IP Modbus Configuration
The PositionServo Drive is a standard ModbusTCP slave device and its IP address, subnet mask and default
gateway can be configured using MotionView software. It supports up to two (2) simultaneous connections
on the standard Modbus TCP port 502. On open connections with no activity for more then 75 seconds, the
PositionServo Drive sends a TCP keep-alive message every 75 seconds to check the connection status.

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2.3 Modbus RTU Implementation Specification
Typical communications between master and slave would be:
• Write commands from Master
- Run command
- Reference values
- Modification of Drive operating parameters
• Read requests from Master
- Reporting of drive status
- Fault status (and fault history)
The PositionServo drive most nearly conforms to the Modicon® Micro 84 in capabilities. This may be of
importance when configuring networks for DDE Servers.The following table identifies the Modbus serial
communication specifications. If the specification is fixed (non-adjustable) the value is shown under “Range”,
if the specification is selectable, the table identifies the Parameter and available range of selections.
Table 1: ModBus Communications Module Parameters
Description Type Range
Baud Rate Selectable 19200, 38400, 57600, 115200
Data Bits Fixed 8
Parity/Stop Bits Selectable Even/1, Odd/1, None1, None2
Network Address Selectable 1 - 247
The following communication parameters are available:
RS485 configuration – If the value of this parameter is ‘Modbus slave’, the modbus slave protocol is enabled
on the RS485 port. If the value is ‘Normal’, the RS485 uses PPP (Point-to-Point Protocol). In Modbus ‘Slave’
mode the drive is configured to receive commands from the Modbus Master.
Modbus Baud Rate – the RS485 baud rate in Modbus mode. The default configuration uses 2 stop bits and
no parity. Stop and parity bits are configurable from the same RS485 configuration menu.
Modbus Reply Delay – The delay introduced after receiving a Modbus request and before sending a reply.
Note that this delay will always be >= 3.5 characters as required by the Modbus specification. Some Modbus
master devices are slow and an increase of the ‘Modbus reply delay’ value may be required to successfully
work with these devices.
Each slave device in the Modbus network must have its own unique network address. The ‘Addr’ submenu
on the drive display and the front panel buttons can be used to set the Modbus network address. The Modbus
Master has no address.
The PositionServo is a Modbus slave device in a single master, multiple slave network. Sometimes slave
devices are named servers because they wait for requests. Therefore the PositionServo drive can be one of
many slaves communicating to the Modbus master. Most terminals are configured as masters with a Modbus
generic driver.
The PositionServo drive uses the required delay of 3.5 characters time between packets to determine the end
of a packet.
The following Modbus functions are supported:
1. 03 (0x03) Read Multiple Holding Registers
2. 16 (0x10) Write Multiple Holding Registers

8P94MOD01B
Note that all parameters in the PositionServo drive are 32 bit values and they cannot be accessed by Write
Single Register functions or Read Holding Register functions with a length of 1 (one 16 bit register). The
user has to use two 16 bit registers to read/write one 32 bit register and for this purpose should reserve 2
consecutive addresses per 32 bit register.
31
Discrete Number
17 16 0 30
ModBus Discrete Number and 32-bit Format
14 1 15
Bit
29 28 27 26 25 24 23 22 21 20 19 18 13 12 11 10 9 8 7 6 5 4 3 2
16
215 1 3 4 567 8 9 10 11 12 13 14
Hex value
x0001
x4000 x0002 x8000 x2000 x1000 x0800 x0400 x0200 x0100 x0080 x0040 x0020 x0010 x0008 x0004
Figure 1: 32 bit Pack Format Discrete Data
The user doesn’t have any discrete functions but can use holding registers with DWORD (integer 32 bit) access
to write discrete values.
When the PositionServo drive receives a Modbus message, the requested function is executed and the drive
can reply with a ‘Normal’ message, an ‘Exception’ Message or a ‘No’ message. These messages are described
in the Modbus Application Protocol Specification V1.1.
The PositionServo drive also supports a Modbus broadcast address. In this case the PositionServo drive receives
a correct Modbus request and executes it without sending any reply back.
The DWORD (double word) and FLOAT numbers are sent with the LOW WORD FIRST convention by the
PositionServo drive.
15
Register_L (Bits 15 ... 0)
1 0 16 14
DWORD_ Unsigned Single Precision 32-bit Format
Register_H (Bits 31... 16)
30 17 31
HByte HByte LByte LByte
13 12 11 10 9 15 8 7 6 54 3 229 28 27 26 25 24 23 22 21 20 19 18
Figure 2: DWORD Format
31
1bit
sign
8 bits
exponent
23 bits
mantissa
23 22 0 30
IEEE 754 Floating Point: Single Precision 32-bit Format
Figure 3: FLOAT Format
Note: Some terminals may have to be configured appropriately in order to accept such a WORD order.

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3. Installation
This section is only applicable to Modbus RTU communication with the RS485 option module, E94ZARS41.
3.1 Mechanical Installation
Install the RS485 Communications Module as illustrated in Figure 4.
Disconnect power from drive and wait 3 minutes.
Remove the two COMM module screws that secure Option Bay 1.
With a flat head screwdriver, pry up the Option Bay 1 cover plate.
Install the RS485 COMM Module (E94ZARS41) in Option Bay 1.
Secure with two COMM module screws (max torque: 0.3Nm/3lb-in).
S921
Figure 4: Installation of RS485 Communications Module

10P94MOD01B
3.2 Electrical Installation
Table 2 and Figure 5 illustrate the pinout of the PositionServo RS485 Option Module E94ZARS41. The 3-pin
connector provides 2-wire plus isolated ground connection to the network.
Table 2: RS485 Interface Pin Designation
Terminal Name Description
1 ICOM Isolated Common
2 TxB (+) Transmit B (+)
3 TxA (-) Transmit A (-)
Figure 5: RS485 Interface Pin Designation
Connections and Shielding
Figure 6 illustrates the connection of the cables for a PositionServo drive in a Modbus master/slave network.
A 120ohm (1%) termination is necessary between the high and low terminals of the first and last slaves in the
network. Note that while ModBus serial protocol supports up to 247 slave addresses, the maximum number
of slave nodes for a network is dictated by the Modbus Master
PLC/PC
Modbus Master
PositionServo
Modbus Slave
PositionServo
Modbus Slave
GND ABGND GND
TxA TxATxB TxB
120Ω
120Ω
Modbus Network
Modbus Network
Figure 6: 120W(1%) Termination in RS485 Network

11 P94MOD01B
4 Modbus Protocol Details
The Modbus protocol defines a simple protocol data unit (PDU) independent of the underlying communication
layers. There are some additional application data unit (ADU) fields introduced by the network layer
ADU
PDU
1 Byte Address 1 Byte Function Code Data 2 Bytes CRC
Figure 7: RS485 Network Modbus Frame
The Master that initiates a Modbus transaction builds the Modbus application data unit. The function indicates
to the server what kind of action to perform. The Modbus application protocol establishes the format of a
request initiated by a client.
The function code field of a MODBUS data unit is coded in one byte. Valid codes are in the range of 1 ... 255
decimal (128 – 255 reserved for exception responses). When a message is sent from a Master to a Server
device the function code field tells the server what kind of action to perform. Sub-function codes are added to
some function codes to define multiple actions.
The data field of messages sent from a master to server devices contains additional information that the
server uses to take the action defined by the function code. This can include items like discrete and register
addresses, the quantity of the items to be handled, and the count of the actual data bytes in the field.
The data field may be nonexistent (of zero length) in certain kinds of requests. In this case the server does not
require any additional information. The function code alone specifies the action. If no error occurs related to
the Modbus function requested in a properly received Modbus ADU, the data field of a response from a server
to a master contains the data requested. If an error related to the Modbus function requested occurs, the field
contains an exception code that the server application can use to determine the next action to be taken.
For example a master can read the ON / OFF states of a group of discrete outputs or inputs or it can read/write
the data contents of a group of registers.
When the server 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 server
simply echoes the original function code.
4.1 Data Transmission
The PositionServo drive uses the RTU (Remote Terminal Unit) transmission mode of the Modbus Protocol and
operates as a Slave device on the network. All devices communicating with the drive(s) must be a Modbus
Master.
The default baud rate for the PositionServo drive is 19200. The default data format is 1 start bit, 8 data bits, no
parity and two stop bits as illustrated in Figure 8.
DATA
Start Bit 1 2 3 4 5 6 7 8 Stop bit Stop bit
Figure 8: Default Data Format

12P94MOD01B
4.2 Register Numbering
Modbus 4X register numbers are always one greater than the actual drive register numbers. For example:
drive register #24 would correspond to Modbus 4X register #25.
4.3 Supported Modbus Function Codes
The function codes supported by the drive are:
1. 03 (0x03) Read Multiple 4X Holding Registers
2. 16 (0x10) Write Multiple 4X Holding Registers
5 Drive Memory Access
The PositionServo drive uses one type of register, (4X Holding Registers) when communicating via Modbus.
Either the RAM copy or the EPM (non-volatile copy) and RAM copy of each register can be accessed at one
time. Each register can be accessed as a 32 bit integer (called DWORD throughout this document) or as a Float
value.
5.1 Mapping from Drive Variable to the Register Address
The memory address ranges are divided into six ranges according to the variable type as shown in Table 3.
Table 3: Memory Address Ranges
Variable Type Memory Range
RAM Integer 0 - 511
RAM Float 512 - 1023
EPM Integer 1024 - 1535
EPM Float 1556 - 2047
RAM 16-bit Integer 2068 - 2303
EPM 16-bit Integer 2304 - 2560
Table 4: Hex to Decimal Number Reference
Hex 0x00 0x1FF 0x200 0x3FF 0x400 0x5FF 0x600 0x7FF 0x800 0x8FF 0x900 0xA00
Decimal 0 511 512 1023 1024 1535 1536 2047 2048 2303 2304 2560
The register address of a drive variable can be calculated by one of the following methods:
NOTE: All values in decimal notation
To access the <variable index> as a RAM-integer, use the following formula to calculate this register address
(maximum address allowed is 511):
<register address> = 0 + 2 * <variable index> + 1;
To access the <variable index> as a RAM-float, use the following formula to calculate this register address
(maximum address allowed is 1023):
<register address> = 512 + 2 * <variable index> + 1;
To access the<variable index> as a EPM-integer, use the following formula to calculate this register address
(maximum address allowed is 1535):
<register address> = 1024 + 2 * <variable index> + 1;

13 P94MOD01B
To access the <variable index> as EPM-float, use the following formula to calculate this register address
(maximum address allowed is 2047):
<register address> = 1536 + 2 * <variable index> + 1;
Two special methods are created for those terminals that can omly handle 16-bit registers:
To access the <variable index> as a RAM- 16 bit integer register (the RAM copy of a variable that is represented
as a 16 bit integer) use the following formula to calculate this register address (maximum address allowed is
2303):
<register address> = 2048 + <variable index> + 1;
For these terminals the values are represented only as integers. The variable index is not multiplied by 2
because one variable is mapped to one register only. If the variable, which is represented as a 32 bit value
internally, is out of range (lower than minimum or higher than maximum value for 16 bit integers), then the
return value is truncated to the closest value supported by the 16 bit signed number. The access to a variable
using this register address range will only read/write the RAM copy of a variable.
To access the <variable index> as an EPM -16 bit signed integer register (the EPM copy of a variable that is
represented as a 16 bit integer) use the following formula to calculate this register address (maximum address
allowed is 2560):
<register address> = 2304 + <variable index> + 1;
For these terminals the values are represented only as integers. The variable index is not multiplied by 2
because one variable is mapped to one register only. If the variable, which is represented as a 32 bit value
internally, is out of range (lower than minimum or higher than maximum value for 16 bit integers), then the
return value is truncated to the closest value supported by the 16 bit register. The access to a variable using
this register address range will read only the RAM copy of a variable and write both the RAM and EPM copies
of a variable.
Register and variable addresses and their mapping based on the type of access are illustrated in Figure 9.
5.2 Register Reading
Use the function code “03 (0x03) Read 4X Holding Registers” to read an adjoining block of holding registers in
a remote device. The request PDU (protocol data unit) specifies the starting register address and the number
of registers. PDU registers are addressed beginning with 0 (i.e. Register #1-16 would be numbered 0-15). The
response is packed two bytes to a register with the binary contents right justified in each byte.
5.3 Register Writing
No discrete register access is provided for PositionServo Drive. Use the “16 (0x10) Write Multiple Registers”
function to write binary values. This requires the user programming to pack bits into user registers.
The function code “16 (0x10) Write Multiple Registers” is used to write a block of adjoining registers (1-123,
Master device dependent) in a remote device. Specify the the requested written values in the request data
field. Data is packed two bytes to a register. A normal response returns the function code, starting address
and number of registers written.

14P94MOD01B
Access X
as decimal
Access X as
32 bit integer
Access X as
32 bit integer
Access X
as decimal
Access X as
16 bit integer
Access X as
16 bit integer
Register X
offset + 0
Register X
offset + 512
Register X
offset + 1024
Register X
offset + 1536
Register X
offset + 2048
Register X
offset + 2304
EPM Location
of variable X
RAM Location
of variable X
EPM Location
of variable X
RAM Location
of variable X
EPM changes
update the
RAM copy
by default
Figure 9: Mapping Register and Variable Addresses based on Access Type
5.4 No Response Conditions
The PositionServo Drive will not respond to any message that:
• contains one or more parity errors
• has an invalid CRC value
• was not directed to the drive’s network address
• is not at least 8 bytes long (minimum required for the supported functions)
• is more than 18 bytes long (maximum allowed before input buffer overflow occurs)

15 P94MOD01B
5.5 Exception Responses
Per Modbus Application Protocol Specification V1.1b, a Modbus Exception response provides the client with the
relevant information concerning the error detected during the processing. The exception function code = the
request function code + 0x80 (an exception code is provided to indicate the reason of the error).
If you try to read a 32 bit register using a read holding register command for one 16 bit register and using the
base address of the register, then it will return the least significant word of the 32 bit register because the
PositionServo drive uses least-significant-word-first rule.
If you try to read a 32 bit register using a read holding register command for one 16 bit register and using the
base address of the register plus one, then it will return the most significant word of the 32 bit register.
Notice that this kind of usage is not useful unless you retrieve both halves of a register and re-build the initial
value on the client/user side. Request for LSW of 32 Bit value as described above gets MSW to be cached.
When MSW is requested, the cached value is returned to allow automatic operation.
If you try to write a 32 bit register using a write multiple register command that writes only one 16 bit register
at a time, then the write command is completed only after you write the second word (MSW). No partial writes
are executed internally to allow automatic operation and ensure 32 bit value integrity.
Modbus as a protocol does not define the formatting of the data in any one or block of registers. The Modbus
Master and slave must both be programmed to interpret the data in the same format.
Exception Codes
If you try to access a function that is not supported by PositionServo drive, the return value is “Illegal Function”
(as defined by “Modbus application Protocol specification V1.1”) which is exception code 0x01.
If you try to access an illegal register address the return code value is “Illegal data address” (as defined by
“Modbus application Protocol specification V1.1”) which is exception code 0x02.
If you try to set a value that is not allowed for a certain variable, the return value is “Illegal Data Value” (as
defined by “Modbus application Protocol specification V1.1”) which is exception code 0x03.

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6 Commissioning
6.1 Drive Monitoring
The network will read the drive parameters as long as Modbus communications are enabled. Set the variable
#175=1 (Modbus); configure variables #172-173 correctly and program the Modbus Master to poll the
appropriate register.
NOTE:
The complete list of variables can be found in Appendix A of the PositionServo
Programming Manual (PM94P01).
6.2 Controlling the Drive
Controlling the drive over Modbus is essentially identical to controlling the drive from the User’s program.
The list of variables and their functionality is identical for both User’s program and Modbus control. Refer to
the variable table in the PositionServo Programming Manual (PM94P01) for the functionality of the drive’s
variables.
6.3 Changing Drive Parameters
To change drive parameters, simply write to the appropriate register as listed in the PositionServo Programming
Manual (PM94P01)
7 Programming Parameters
NOTE:
The complete list of variables can be found in Appendix A of the PositionServo
Programming Manual (PM94P01).
Drive variables #172-176 are RS-485 communication programming parameters specifically for configuration
of the RS-485 interface.
7.1 Negative Number Transmission
Drive variables 51, 60, 79, 81 and 90 are signed integer values and could be negative (refer to drive User
and Programming manual for details on these parameters). These registers are sent over the modbus
communications in signed internal units.

AC Technology Corporation
www.actech.com
630 Douglas Street
Uxbridge, MA 01569
Telephone: [phone]
Facsimile: [phone]
P94MOD01B