Nord Drivesystems SK 700E Series Instructions and recipes

SK TU1-DEV
SK TU2-DEV
SK TU3-DEV
GB
BU 0050
USS Bus modules and MODBUS RTU
Supplementary manual for NORD frequency inverters

NORD USS and Modbus RTU Manual Safety information
2 Subject to technical amendments BU 0050 GB-3111
N O R D Frequency inverters
Safety and operating instructions for
drive power converters
(as per: Low Voltage Directive 2006/95/EEC )
1. General
During operation, drive power converters may, depending on their
protection class, have live, bare, moving or rotating parts or hot
surfaces.
Unauthorised removal of covers, improper use, incorrect installation
or operation causes a risk of serious personal injury or material
damage.
Further information can be found in this documentation.
All transportation, installation, initialisation and maintenance work
must be carried out by qualified personnel (compliant with
IEC 364, CENELEC HD 384, DIN VDE 0100, IEC 664 or
DIN VDE 0110, and national accident prevention regulations).
For the purposes of these basic safety instructions, qualified
personnel are persons who are familiar with the assembly,
installation, commissioning and operation of this product and who
have the relevant qualifications for their work.
2. Proper use in Europe
Drive power converters are components intended for installation in
electrical systems or machines.
When installed in machines, the drive power converter cannot be
commissioned (i.e. commencement of the proper use) until it has
been ensured that the machine meets the provisions of the EC
Directive 2006/42/EEC (Machine Directive); EN 60204 must also be
complied with.
Commissioning (i.e. implementation of the proper use) is only
permitted if the EMC Directive (2004/108/EEC) is complied with.
Drive power converters with the CE mark meet the requirements of
the Low Voltage Directive 2006/95/EEC. The harmonized standards
stated in the Declaration of Conformity are used for the drive power
converters.
Technical data and information for connection conditions can be
found on the name plate and in the documentation, and must be
complied with.
The drive power converters may only be used for the safety
functions which are described and for which they have been
explicitly approved.
3. Transport, storage
Information regarding transport, storage and correct handling must
be complied with.
4. Installation
The installation and cooling of the equipment must be implemented
according to the regulations in the corresponding documentation.
The drive power converters must be protected against
impermissible loads. Especially during transport and
handling, components must not be deformed and/or
insulation distances must not be changed. Touching of
electronic components and contacts must be avoided.
Drive power converters have electrostatically sensitive
components, which can be easily damaged by incorrect
handling. Electrical components must not be mechanically
damaged or destroyed (this may cause a health hazard!).
5. Electrical connections
When working on live drive power converters, the applicable
national accident prevention regulations must be complied
with (e.g. VBG A3, formerly VBG 4).
The electrical installation must be implemented according to
the applicable regulations (e.g. cable cross-section, fuses,
ground lead connections). Further information is contained
in the documentation.
Information about EMC-compliant installation –such as
shielding, earthing, location of filters and installation of
cables can be found in the drive power converter
documentation. These instructions must be complied with
even with CE marked drive power converters. Compliance
with the limiting values specified in the EMC regulations is
the responsibility of the manufacturer of the system or
machine.
6. Operation
Where necessary, systems where drive power converters
are installed must be equipped with additional monitoring
and protective equipment according to the applicable safety
requirements, e.g. legislation concerning technical
equipment, accident prevention regulations, etc.
The parameterisation and configuration of the drive power
converter must be selected so that no hazards can occur.
All covers must be kept closed during operation.
7. Maintenance and repairs
After the drive power converter is disconnected from the
power supply, live equipment components and power
connections should not be touched immediately, because of
possible charged capacitors. Observe the relevant
information signs located on the drive power converter.
Further information can be found in this documentation.
These safety instructions must be kept in a safe place!

NORD USS and Modbus RTU Manual Concerning this document
BU 0050 GB-3111 Subject to technical amendments 3
Documentation
Designation: BU 0050 GB
Part No.: 607 05 01
Device series: USS for SK 300E, SK 500E (entire series), SK 700E, SK 750E
Modbus RTU for SK 540E and SK 545E
Version list
Designation of
previous issues
Software
Version
Comments
BU 0500 GB, December 2004
Part No. 607 0502 / 5204
Latest version
BU 0050 GB, August 2011
Part No. 607 0502 / 3111
Deletion of option "DevicenNet mc" for FI series
"vector mc"
Inclusion of SK 500E series frequency inverters
Implementation of Modbus RTU (for SK 500E)
Publisher
Getriebebau NORD GmbH & Co. KG
Rudolf-Diesel-Str. 1 D-22941 Bargteheide http://www.nord.com/
Tel.: [phone] / 401-0 Fax [phone] / 401-555
NOTE
This supplementary operating manual is only valid in conjunction with the operating manual
supplied for the respective frequency inverter.

NORD DeviceNet Manual Concerning this document
4 Subject to technical amendments BU 0050 GB-3111
Intended use of the frequency inverter
Compliance with the operating instructions is necessary for fault-free operation and the
acceptance of any warranty claims. These operating instructions must be read before
working with the device!
These operating instructions contain important information about servicing. They must
therefore be kept close to the device.
The described optional modules can only be used for the specifically defined frequency
inverter series, use across series is only possible with the SK TU2-… module with SK 300E
and SK 750E. The use of these modules with other devices is not permitted and can lead to
their destruction.
The described optional modules and the corresponding frequency inverters are devices for
stationary installation in control cabinets or decentralised structures. All details
regarding technical data and permissible conditions at the installation site must be
complied with.
Commissioning (commencement of the intended use) is not permitted until it has been ensured
that the machine complies with the EMC Directive 204/108/EEC and that the conformity of
the end product meets the Machinery Directive 2006/42/EEC (observe EN 60204).
Getriebebau NORD GmbH & Co. KG, 2011

Contents
BU 0050 GB-3111 Subject to technical amendments 5
FOREWORD ................................................................................................................................7
1 USS ...........................................................................................................................................7
1.1 General information..............................................................................................7
1.1.1 The USS Protocol .....................................................................................................7
1.1.2 Features....................................................................................................................7
1.1.3 Delivery.....................................................................................................................7
1.1.4 Scope of supply.........................................................................................................8
1.1.5 Certifications.............................................................................................................8
1.1.6 Identification System.................................................................................................8
1.2 Modules................................................................................................................9
1.2.1 SK 500E....................................................................................................................9
1.2.2 SK 700E..................................................................................................................12
1.2.3 SK 300E..................................................................................................................18
1.3 USS Protocol Specification ................................................................................19
1.3.1 General information.................................................................................................19
1.3.2 Telegram Structure .................................................................................................19
1.3.3 Data Coding............................................................................................................20
1.3.4 Character Frame.....................................................................................................20
1.3.5 Transfer Procedure.................................................................................................21
1.3.6 Start Pause Time ....................................................................................................21
1.3.7 Response Delay Time.............................................................................................22
1.4 Bus Configuration...............................................................................................23
1.4.1 General information.................................................................................................23
1.4.2 Topology.................................................................................................................23
1.4.3 Transfer Method......................................................................................................23
1.4.4 Installation of the Bus System.................................................................................24
1.5 Data transmission...............................................................................................26
1.5.1 Structure of reference data .....................................................................................26
1.5.2 PPO types...............................................................................................................27
1.5.3 Process data (PZD).................................................................................................29
1.5.4 Parameter range (PKW)..........................................................................................39
1.6 Telegram examples............................................................................................43
1.6.1 The Macro Generator..............................................................................................43
1.6.2 Switch-on block Standby....................................................................................44
1.6.3 Enable with 50% setpoint........................................................................................46
1.6.4 Writing a parameter.................................................................................................47
1.6.5 Reading the acceleration time parameter ...............................................................48
1.7 Master Telegram Times .....................................................................................49
1.8 Frequency Inverter Settings ...............................................................................50
1.8.1 Frequency inverter bus parameters ........................................................................50
2 MODBUS RTU........................................................................................................................61
2.1 The bus system..................................................................................................61
2.2 Features .............................................................................................................61
2.3 Telegram Structure.............................................................................................62
2.4 RTU Frames.......................................................................................................62
2.5 Function Codes ..................................................................................................62
2.5.1 01h Read Coil .........................................................................................................63
2.5.2 05h Write Single Coils.............................................................................................63
2.5.3 0Fh Write Multiple Coils..........................................................................................64
2.5.4 03h Read Holding Register.....................................................................................65
2.5.5 06h Write Single Register .......................................................................................66
2.5.6 10h Write Multiple Register.....................................................................................66
2.6 Exception Responses.........................................................................................68
2.7 Watchdog ...........................................................................................................68
2.8 Description of parameters ..................................................................................69

NORD USS and Modbus RTU Manual
6 Subject to technical amendments BU 0050 GB-3111
3 FAULTS.................................................................................................................................. 71
3.1 Troubleshooting................................................................................................. 71
3.1.1 Error display............................................................................................................71
3.1.2 Error memory..........................................................................................................71
3.2 Error messages ................................................................................................. 72
4 ADDITIONAL INFORMATION............................................................................................... 73
4.1 Maintenance and servicing information............................................................. 73
4.2 Abbreviations in this manual.............................................................................. 73
5 KEYWORD INDEX................................................................................................................. 74

1.1 USS - General information
BU 0050 GB-3111 Subject to technical amendments 7
Foreword
This supplementary documentation is valid for the SK 300E, SK 500E, SK 700E series and for the SK 750E.
It describes the setup of communication via RS485.
For this, the main emphasis is on communication according to the USS protocol. Corresponding optional
modules are available for the SK 700E and SK 750E series. The SK 300E and SK 500E series have an
appropriate interface integrated as standard.
In addition, the requirements of Modbus communication (SK 540E and higher) will be considered.
1 USS
1.1 General information
1.1.1 The USS Protocol
With the aid of the USS protocol, a user can set up a serial bus coupling between a higher level Master and
several slave systems. Master systems can for example be memory programmable control units (SPS) or
PCs.
The USS protocol allows the user to implement automation tasks with conveying according to time-cycled
telegram traffic (fixed telegram length required), as well as visualisation tasks.
The USS protocol is a simple, serial transfer protocol defined by Siemens, which if fully tailored to the needs
of drive technology.
1.1.2 Features
Support of a multiple point coupling, e.g. EIA RS 485 hardware or a point-to-point coupling, e.g. EIA RS 232.
Master / Slave access procedure
Single Master System
Maximum 32 participants (maximum 31 slaves)
Simple, secure telegram framework
Same physical bus design as PROFIBUS (DIN 19245 Part 1)
The data interface to the basic device is according to the PROFILE for variable speed drives.
This means that with USS, the information to the drive unit is transferred in the same way as with the
PROFIBUS-DP.
Can be used for commissioning, service and automation
Service tools on PC (NORD CON)
Simple to implement in customer-specific systems-
1.1.3 Delivery
Check the equipment immediately after delivery/unpacking for transport damage such as deformation or
loose parts.
If there is any damage, contact the carrier immediately and carry out a thorough assessment.
Important! This also applies even if the packaging is undamaged.

NORD USS and Modbus RTU Manual
8 Subject to technical amendments BU 0050 GB-3111
1.1.4 Scope of supply
SK TU1-RS232* for frequency inverter SK 700E IP20 or
SK CU1-STD for frequency inverter SK 700E, SK 750E IP20 or
SK CU1-USS for frequency inverter SK 700E, SK 750E IP20 or
*incl. screw for optional fixing to the FI
1.1.5 Certifications
1.1.5.1 European EMC Directive
If NORD frequency inverters or their options are installed according to the
recommendations in this instruction manual, it meets all EMC directive
requirements, as per the EMC product standard for motor-operated systems
EN 61800-3.
1.1.5.2 RoHS compliance
The bus options described here are designed to be RoHS compliant
according to Directive 2002/95/EEC
1.1.6 Identification System
SK TU1-RS2
Bus system: AS1 = AS-Interface, CAN = CAN, CAO = CANopen,
RS2 = RS232, USS = USS, etc.
Device series: SK TU1 / SK TU2 / SK TU3

1.2 USS - Modules
BU 0050 GB-3111 Subject to technical amendments 9
1.2 Modules
1.2.1 SK 500E
1.2.1.1 General
By the use of various modules for display, control and parameterisation, the SK 5xxE can be easily adapted
to various requirements.
Alphanumerical display and operating modules can be used for simple commissioning. For more complex
tasks, various connections to a PC or an automation system can be selected.
The technology unit (Technology Unit, SK TU3-…) is connected externally to the frequency inverter and is
therefore easy to access and replace at any time.
As delivered, without the technology unit, 2 LEDs (green/red) are visible externally. These indicate the actual
device status.
The green LED indicates that the mains voltage is present and operational, while a flashing code that
increases in speed shows the degree of overload at the frequency inverter output.
The red LED signals actual error by flashing with a frequency which corresponds to the number code of the
error (Manual BU 0500 Section 6).
WARNING
NOTE
Modules should not be inserted or removed unless the device is free of voltage. The slots may
only be used for the intended modules.
Installation of a technology unit separate from the frequency inverter is not possible. It must be
connected directly to the frequency inverter.
LED
red/green

NORD USS and Modbus RTU Manual
10 Subject to technical amendments BU 0050 GB-3111
1.2.1.2 RS 485 interface
As standard, all devices in the SK 500E series have an integrated interface for USS bus communication.
According the version of the Fi, the following interfces are available:
X11 RJ12 socket (available for the entire series)
X7:73/74 RS485 + / - terminal connection (available for SK 520E or higher)
X7: additional terminal
block with RS485
interface
(terminals 73/74)
SK 520Eor higher
X11:1x RJ12 socket to
connect the RS232
or RS485 interface
X11

1.2 USS - Modules
BU 0050 GB-3111 Subject to technical amendments 11
RJ 12 socket (X11)
In addition to the RS485 interface, the RJ12 socket also provides an interface for communication via RS 232.
However, the RS232 interface is only intended for connecting a PC.
If a network is to be set up with several participants which communicate via USS (frequency inverters), it
must be noted that communication must be via RS 485.
The RS232 interface (contacts X11:TXD and X11:RXD) cannot be deactivated on the frequency inverter. In
order to prevent a short circuit of these data cables and therefore the destruction of the RS232 driver, the
contacts TXD, RXD and +5V must not have a common connection to several frequency inverters.
Contact
Function
Data
Description / wiring suggestion
DIP switch 1/2 (top side of frequency inverter)
DIP-1
Termination resistor for RS485 interface
(RJ12); ON = switched in
[Default = "OFF"]
For RS232 communication DIP1 to "OFF"
X11 X10 X9
VREF 10V AGN D 0V AIN 1+ AIN 2 + AO UT 1 D IG IN 1 D IG IN 2 DIG IN 3 D IG I N 4 VO + 15 V D G N D 0V
11 12 13 14 16 22 23 24 25 42 40 21
DIG IN 5
1 2 3 4
REL 2.2 REL 2.1 REL1.2 REL 1.1 CAN _H CAN _L CAN _G N D nc CAN _SHLD CAN _GN D nc CAN _24V CAN _H CAN _L CAN _G N D nc CAN _SH LD CAN _G N D nc CAN _24V RS485_A RS4 85_B G N D TXD RXD
41VO + 5V
+ 5V
1 2
ON
VREF 10V AGN D 0V AIN 1+ AIN 2+ AOUT 1 DIG IN 1 DIG IN 2 DIG IN 3 DIG IN 4 VO + 15V DGN D 0V
11 12 13 14 16 22 23 24 25 42 40 21
DIG IN 5
1 2 3 4
REL 2.2 REL 2.1 REL1.2 REL 1.1
CAN _H CAN _L CAN _G N D nc CAN _SH LD CAN _G N D nc CAN _2 4V CAN _H CAN _L CAN _G N D nc CAN _SH LD CAN _G N D nc CAN _2 4V
RS485_A RS485_B GN D TXD RXD
41
VO + 5V
+ 5V
SK 511E and above
RS232/485 DIP CAN/CANopen
DIP-2
Termination resistor for CAN/CANopen
interface (RJ12); ON = switched in
[Default = "OFF"]
Terminal connection (X7:73/74)
Above configuration level SK520E the frequency inverters are equipped with an additional terminal block
(X7). This provides the possibility of setting up the RS485 bus communication via contacts 73 and 74.
Terminal
Function
Data
Description / wiring suggestion
X7:73
Data cable RS485
Baud rate
9600…38400Baud
Termination resistor
R=120
BUS connection parallel to RS485 on RJ12 plug
NOTE: The termination resistance of DIP switch 1 (see
RJ12/RJ45) can also be used for contacts 73/74.
X7:74
NOTE
To ensure reliable communication, a termination resistor (DIP switch DIP1) must be set at both
ends of the bus.

NORD USS and Modbus RTU Manual
12 Subject to technical amendments BU 0050 GB-3111
Technology units (Technology Units) are modules which can be inserted
from above for display, parameterisation and control of the inverter.
1.2.2 SK 700E
1.2.2.1 General
With the combination of modules for display, technology units and modules with digital and analog inputs
and interfaces, customer interfaces or special extensions, the SK 700E can be easily extended to cater
for the requirements of a wide range of applications.
WARNING
NOTE
Modules must not be inserted or removed unless the device is free of voltage. The slots may
only be used for the intended modules. The slots are coded to prevent them from being
incorrectly connected.
Installation of a technology unit separate from the frequency inverter is not possible. It must be
connected directly to the frequency inverter.
Customer interfaces (Customer Units) are modules which are
inserted into the upper slot inside the inverter. They are used for
control and communication using digital/analog signals or bus
interfaces.
Special extensions (EXtension Units) are inserted into the lower slot of
the inverter. Such an extension unit is required if the speed is to be
controlled or positioning is to be carried out by an incremental (absolute)
encoder.

1.2 USS - Modules
BU 0050 GB-3111 Subject to technical amendments 13
1.2.2.2 Technology Box RS232
(SK TU1-RS2, Option)
The Technology Box (Technology Unit) is clipped to the outside of the inverter.
The RS232 interface enables simple connection of an SK 700E to a PC with a
serial interface.
Communication between PC and frequency inverter can be set up using the
NORD CON Software (Windows). This is used for the control, parameterisation
and display of operating values of the frequency inverter.
This allows a simple functional test of the inverter to be carried out and,
following successful parameterisation, the data set can be saved as a file.
1.2.2.3 Installation of the SK TU1 technology unit
Installation of the technology units must be carried out as follows:
1. Switch off the mains voltage, observe the waiting period.
2. Remove the dummy cover by actuating the unlocking device on the top and bottom edge.
3. Allow the technology unit to engage audibly by pressing lightly on the mounting surface.
WARNING
NOTE
Modules must not be inserted or removed unless the device is free of voltage. The slots may
only be used for the intended modules.
Installation of a technology unit separate from the frequency inverter is not possible. It must be
connected directly to the frequency inverter.
RXD
0V
TXD
6
1
5
9
5V
700E
N O RD A C
700E
N O RD A C

NORD USS and Modbus RTU Manual
14 Subject to technical amendments BU 0050 GB-3111
1.2.2.4 Customer unit Standard I/O
(SK CU1-STD, Option)
The standard I/O of the customer interface(Customer Unit) provides
sufficient control terminals for most applications and it is fully
terminal-compatible with NORDAC vector mc..
1 analog differential input, 4 digital inputs and 1 analog output are
available for control of the frequency inverter.
Readiness for operation is shown via the 2 relay contacts and a
mechanical motor brake is activated at the correct time.
The connected frequency inverter can be accessed via the RS485
interface. In addition to the entire range of control functions,
parameterisation is also possible.
TheNORD CON software can be used to carry out a simple function
test of the serial interface and the parameterisation of the inverter.
For this, an interface converter (e.g. SK IC1-232/485) must be used
between the PC and the inverter. Following successful
parameterisation, the complete data set can be stored as a file by
means of NORD CON.
Connector
Functions
Maximum cross-section
Parameter
X1.1
Output relay
1,5 mm2
P434 ... P443
X1.2
Analog signals IN / OUT
1,0 mm2
P400 ... P419
X1.3
Digital inputs
1,0 mm2
P420 ... P423
X1.4
Bus signals / power supply
1,0 mm2
P503 ... P548
74 RS485 -
X1.1 X1.2 X1.3 X1.4
11 VREF 10V
12 AGND/0V
13 AIN1 -
14 AIN1 +
17 AOUT1
21 DIG IN 1
22 DIG IN 2
23 DIG IN 3
24 DIG IN 4
42 VO+15V
41 VO+5V
40 GND /0V
73 RS485 +
01 REL1.1
02 REL1.2
03 REL2.1
04 REL2.2
NOTE: All control voltages are based on a common reference potential!
Potentials AGND /0V and GND /0V are internally linked in the device.
The maximum total current 5/15V is 300mA!
Potentialfreier Kontakt oder
Ausgang einer SPS: 7,5...33V
(low = 0...3,5Volt)
Differenzeingang 0...10V
0...20mA
Voltage supply: 5V
RS 485 (USS protocol)
5V supply for ParameterBox,
p-box or motor thermistor
Data cables USS protocol
Digitale Eingänge:
DIG IN 1 = Ein rechts
DIG IN 2 = Ein links
DIG IN 3 = Parametersatz bit 0
DIG IN 4 = Festfrequenz 1
Ausgangsrelais:
max. 2,0A
28V DC /230V AC
UREF = 10V / Imax = 10 mA
Analogausgang SPS: 0...10V
oder Potentiometer: 2...10k
Spannungsversorgung: 15V
Termination resistor for
RS 485 interface (120)
Zuschaltbarer Bürdenwiderstand für
0/4...20mA Analogeingang (250)
U/I switching
Analog input,
250
ON = Current,
OFF = Voltage
Termination
resistor
RS 485
120
O
F
F
ON
O
F
F
ON

1.2 USS - Modules
BU 0050 GB-3111 Subject to technical amendments 15
1.2.2.5 USS Customer Interface
(SK CU1-USS, Option)
In addition to data connections, the USS customer units are also
equipped with conventional digital inputs and outputs.
Via the existing relay contacts, a mechanical motor brake can be
controlled or readiness for operation can be communicated to a
higher level system.
The digital input has a 2.5V switching threshold for the evaluation
of the temperature sensor. The input can, however, also be used
for an emergency stop function.
Connector
Functions
Maximum cross-section
Parameter
X4.1
Output relay
1,5 mm2
P434 ... P436
X4.2
Digital input
1,5 mm2
P420
X4.3
Data cables
1,5 mm2
P503 ... P548
NOTE: All control voltages are based on a common reference potential!
Potentials AGND /0V and GND /0V are internally linked in the device.
The maximum total current 5/15V is 300mA!
X4.1 X4.2 X4.3
01 REL1.1
02 REL1.2
41 VO+5V
40 GND/0V
73 RS485+
74 RS485-
21 DIGIN1
42 VO+15V
Data cables:
RS485
(terminal 73-74, RS485 +/-)
Control signal: 2.5 ... 33V
Output relay:
Max. 2.0A
28V DC /230 V AC
Digital input 1 (P420)
Voltage supply: 15V
USS
USS termination resistor
not connected
connected
ON
OF
F

NORD USS and Modbus RTU Manual
16 Subject to technical amendments BU 0050 GB-3111
1.2.2.6 Installation of customer units
WARNING
NOTE
Installation must be carried out by qualified personnel only, paying particular
attention to safety and warning instructions.
A customer interface must not be replaced while it is carrying voltage.
1. Switch off the mains voltage, observe
the waiting period.
2. Remove the cover grid from the
connection area by loosening the 2
screws and levering out the device cover
(slot) or simply pull it out.
3. Locking lever in the "open" position.
4. Using light pressure push the customer
unit into the upper guide rail until it
engages.
5. Move the locking lever to the "closed"
position.
6. Remove the connector by pressing the
releases then make the necessary
connections. Then insert the connectors
until they engage.
7. Replace all covers.
Kundenschnittstelle
Sondererweiterung
Technologiebox
Verrieglungsstift
CLOSED
OPEN
Verriegelung geschlossen
Verriegelung geöffnet
Locking pin
Technology unit
Customer interface
Special extension
unit
Locking device closed
Locking device open

1.2 USS - Modules
BU 0050 GB-3111 Subject to technical amendments 17
Removing customer units:
1. Switch off the mains voltage, observe the waiting period.
2. Remove the cover grid from the connection area by loosening the 2 screws and levering out the device
cover (slot) or simply pull it out.
3. Locking lever in the "open" position.
4. Using a screwdriver (as shown), lever the customer unit out of its engaged position and then remove it by
hand.
5. Move the locking lever to the "closed" position.
6. Replace all covers.
Motor temperature protection applies for all customer units!
For secure protection against motor overheating, a
temperature sensor (thermistor, PTC) can be connected
to any digital input.
The appropriate parameters (P420 ... P425, depending on
option) must be set to a value of 13 (PTC thermistor input)
for this purpose.
The supply voltage varies dependent upon the customer
unit. The lowest voltage possible should be chosen.
Internal switching in the inverter prevents excessive PTC
voltage.
The cable routing should always be separate from the motor cable and with shielded cables.
Motor
PTC
Supply voltage
+5V
Digital
input

NORD USS and Modbus RTU Manual
18 Subject to technical amendments BU 0050 GB-3111
1.2.3 SK 300E
Technology units and customer interfaces
Through the combination of modules for the
display, (technology units) and modules with
digital and analog inputs, as well as interfaces,
(customer units) or bus interfaces, the SK 300E
can be easily adapted to the requirements of a
wide range of applications.
The NORD CON software can be used to carry
out a simple function test of the serial interface
and parameterisation of the inverter. For this, an
interface converter (e.g. SK IC1-232/485) must
be used between the PC and the inverter.
Following successful parameterisation, the
complete data set can be stored as a file by
means of NORD CON.
Further details can be found in Manual BU 0300.
USS interface (RS485)
With the SK 300E, an RS485 interface is lead out to a 4-pin M12
round connector (Detail 1) as standard. In addition to being used
for external control (ParameterBox) it can also be used as a bus
interface.
If required an M12 SUB D9 (Part No.. 278910060) connecting
cable is available.
Parallel to the external M12 connection, in the connection unit
(trio interface, removed from FI) terminals 73/74 are also
available for connection.
The RS485 termination resistor (Detail 2) can be switched in or
out using the DIP switch in the connection unit.
M12 connector (Detail 1)
Terminal (Detail 2)
Functions
Maximum cross-section
4 (black)
73
RS485 +
1,5 mm2
3 (blue)
74
RS485 -
1,5 mm2
2 (white)
41
+5V
1,5 mm2
1 (brown)
40
0V, GND
1,5 mm2
3,0 m
1
2

1.3 USS - Protocol speciication
BU 0050 GB-3111 Subject to technical amendments 19
1.3 USS Protocol Specification
1.3.1 General information
The USS protocol defines an access procedure according to the Master/Slave principle for communication
via a serial bus. A sub-set of this also includes point-to-point connection. A master and a maximum of 31
slaves can be connected to a bus. The individual slaves are accessed by the master via an address
character in the telegram. Direct exchange of messages between the individual slaves is not possible.
Communication is carried out in semi-duplex mode. The master function cannot be transferred (single master
system).
Data transfer via the two-cable bus is carried out by individual characters in the format:
1 start bit, 8 data bits 1 even parity bit and 1 stop bit (8E1) - This results in a character frame of 11 bits.
The direction of the data on the bus (transmit or receive) is specified by the master.
1.3.2 Telegram Structure
Each telegram starts with the start character STX (= 02 Hex), followed by the length (LGE) and the address
byte (ADR). This is followed by the information characters. The telegram
is concluded by the data saving character BCC (Block Check Character).
STX
LGE
ADR
N1
N2
..
Nn
BCC
For word information (16 Bit) in the information data block (= information character block) the High Byte (first
character) is always transmitted first, followed by the Low Byte (second character). The same applies for
double-word information:
First the High Word is transmitted, followed by the Low Word.

NORD USS and Modbus RTU Manual
20 Subject to technical amendments BU 0050 GB-3111
1.3.3 Data Coding
STX
(Start of Text): ASCII character: 02 Hex
The start character forms the first character in the telegram and together with the start pause it is used
for reliable detection of the start of the telegram.
LGE
(Telegram length): 1 Byte, contains the length of the telegram.
The telegram length is located in the 2nd byte of the telegram and indicates the length of the telegram
from the 3rd byte onwards. Specification of the length enables differentiation between the various types
of telegram. The data recipient can use the length byte to check the number of characters to be
received.
ADR
(Address byte): 1 byte, also contains the slave address.
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
0 M BC | Address (0..30) |
The USS address is located in the 3rd byte (data bits 0 to 4) of the telegram. The slave device which is
to transmit or receive data is identified via the USS address. Therefore, a maximum of one slave device
can be represented by each of the 31 possible addresses For this, the appropriate address must be set
in the slave device. Bit 5 and Bit 6 have a special meaning.
Bit 5 Broadcast: A so-called broadcast telegram can be triggered by setting this bit. In a broadcast
telegram, address bits 0 to 4 are ignored by the connected slaves, i.e. the transmitted telegram is
processed by all of the slaves. However, in contrast to standard addressing, the slaves do not transmit a
response telegram as this would result in bus conflicts.
Bit 6 Echo: By setting the 6th bit, the inverter returns a telegram which is identical to the one which it
has received (for commissioning).
N1... Nn
Information characters: each one byte, content depending on task
BCC
1 byte, data saving character (Block Check Character)
The check-sum BCC is formed byte-wise over the entire telegram as an Exclusive OR link. The result
after the last net character is then the BCC.
BCC = STX XOR LGE XOR ADR XOR N1XOR....NN
1.3.4 Character Frame
Each transmitted character begins with a start bit (logical 0) and end with a stop bit (logical 1). 8 bits (1 byte)
are transmitted. Saving is performed by a parity bit (even parity). Therefore 11 bits are transmitted for each
character.