Integrating IO-Link Devices into CIP Networks
Frank Moritz
Product Manager Sensors & Connectivity
SICK AG
Presented at the ODVA2012 ODVA Industry Conference & 15th Annual Meeting
October 16-18, 2012
Stone Mountain, Georgia, USA
Abstract
IO-Link was introduced in factory automation in year 2009 as a new communication interface for small sensors andactuators. By now more than 50 companies are using IO-Link in their products and are supporting IO-Linktechnology. This communication technology allows integration of small devices from different vendors into any
field buses or PLCs. The actual IO-Link Version is V1.1 and is being standardized in IEC 61131-9. Because of theinterest of user, ODVA has formed an IO-Link Integration SIG to consider the specifications for integration of IOLink devices into a CIP Network.

Keywords
IO-Link, Industrial Communication, IODD, IEC 61131-9, SDCI, process data transmission, device description

Definition of terms
DeviceIO-Link sensor or actuator.
Direct Parameters
directly (page) addressed parameters transferred acyclically via the page communication channel without
acknowledgement.
IO-Link Master
active peer connected through ports to one up to n Devices and which provides an interface to the gateway to theupper level communication systems or PLCs.
IODD
XML based document describing the data objects of an IO-Link device.
SDCIIO-Link specification in IEC 61131-9.

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IO-Link at a Glance
End user requirements
Today microcontroller based intelligent small sensors and actuators (devices) have a lot of different built-inparameters. End users need to optimize these parameters specific to an application like presence sensing of targets.
To allow changing these parameters, devices need a communication interface for data transmission. A field bus
connection is often not feasible to implement due to space or cost restrictions.
End users are requesting an easy-to use low cost communication interface for factory automation which can be
implemented even into the smallest sensors like magnetic cylinder sensors.
Users are asking for functionality like:
Expanded diagnostics- Diagnostics including remote diagnostics down to the field device level- Cable break detection- Device-specific diagnostics
Simplified installation- Replace parallel wiring by one simple cable- Replace analog signal types by digital transmission- Standardize interfaces and cables with a single type
- Modular machine concepts shall be inherently supported
Automated parameter setting- Function modules for automated parameter setting- Tool-assisted parameter setting
Other key requirements include:-The communication interface shall have the functionality of transmitting cyclic process data as well as
acyclic data.
Cycle times for process data shall meet the requirements for typical factory automation applications.
The cycle time shall be scalable, providing process data transmission within 2ms.
The communication interface shall be suitable for sensors and actuators as well and work reliably in afactory automation environment, therefore meeting all EMC requirements.

Users want to have a more robust high resolution transmission of analog 16 bit process data. For transmission of thebeam status of a light grid a maximum of 256 bits shall also be transmitted via process data.
Each device shall have a unique ID for the identification of sensor / actuators in remote application.
Users are also asking for a fast setup and integration of devices into their specific control equipment (like PLCs orHMIs). Due to the fact that today sensors are connected to PLCs via various field buses, users want to have an easy
integration of their preferred sensors into all of these different field buses.
Easy integration into different field buses requirement- The communication interface standard should have no restrictions and have to be open to any vendor or
supplier for masters and devices.
- Users want to have an accepted technology all over the world, fitting into all PLCs and field buses.
- All devices shall to be integrated into specific engineering tools in an easy way.
- Managing overhead using addresses, switches and bus administration should be avoided.
Users as well as suppliers request to have much lower additional costs than for a direct field bus connection.
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Extended features like easy and fast device exchange shall be supported by downloading device parameters andconfiguration data in an automatic fast and reliable way.
Users want to have backward compatibility to switching sensors and have the advantage of not to make a systemdecision when they use this communication interface.

Technical overview
The IO-Link technology defines a generic interface for connecting sensors and actuators to a master unit, which may
be combined with gateway capabilities to become a fieldbus remote I/O node. The domain of this technology isshown in Figure 1:Figure 1: Domain of the IO-Link technology within the automation hierarchy
The IO-Link technology covers a number of topics. The domain of devices is the sensors and actuators in thefactory automation field. These devices are near or direct in the process of a machine application.
The masters typically have a gateway application and are connected to a field bus. Therefore masters are connecting
IO-Link devices to a fieldbus or a PLC. IO-Link is closing the communication gap of the so called “last mile” tosmall devices (Figure 2).

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Figure 2: IO-Link on the last mile
The physical topology of IO-Link (Figure 3) is point-to-point from each Device to the Master using 3 wires overdistances up to 20 m. The IO-Link physical interface is backward compatible with the usual 24 V I/O signalling
specified in IEC 61131-2. 3 Transmission rates of 4,8 kbit/s, 38,4 kbit/s and 230,4 kbit/s are supported.

Figure 3: Physical topology of IO-LinkIO-Link is compatible to IEC 61131-2 (Figure 4) and supports the digital input functionality “SIO” (standard inputoutput) as well as communication on sensor devices and also on masters. A master is able to switch at any time from
SIO mode to communication mode with the different transmission rates COM1, COM2 and COM3 and vice versa.
While a device supports exactly one transmission rate, the masters have to support all 3 transmission rates

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Figure 4: IO-Link compatibility with IEC 61131-2
Once activated, the IO-link mode supports parameterization, cyclic data exchange, diagnosis reporting,identification & maintenance information, and external parameter storage for device backup and fast reload ofreplacement devices.

Data model of IO-Link devices
The data model of IO-Link devices covers process data, parameters, commands and diagnosis (events) (Figure 5).
The address range allows the addressing of 65536 data objects which is restricted for IO-Link to 16364 data objects.
The objects are accessible via indices and sub-indices. Each object can obtain simple or structured data types.
Structured data types are combinations of simple types like integer, octets, strings or records.

Figure 5: Data model of IO-Link
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Device Description IODD
All user accessible data objects, the content as well as their structure are described in the IODD.
The IODD is a XML based device description file which is mandatory for all devices.
Inside the IODD, the content as well as the structure of data objects is described. Importing and interpreting thisIODD enables tools to have an automatic access to parameters and also the right representation of data supported.
This enables user-friendly integration into PLC-engineering tools or into an FDT container environment.
In Figure 6 a part on an IODD is shown as an example. A representation of an IODD on a PC based graphical userinterface is shown in Figure 7.

Figure 6: part of an IODD

Figure 7: IODD representation inside a FDT container

All acyclic and cyclic data are transmitted through the IO-Link communication channel and split via the System
Management to the different Application Layer services. In Figure 8 the object transfer at the application layer levelis shown.

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Figure 8: Object transfer at the application layer level
For an optimized data transmission different frame types are supported the data link layer (Figure 9). Each frame istransmitting one or more bytes of acylic (OD on-request data) and cyclic data (PD process data). Each frame
contains the master request (started by MC) and device response. The master request, as well as the device response,is secured by an additional checksum (CKT and CKS).
A typical frame for transmitting 8 bits of process data of a sensor is TYPE_2_1 which takes 2.3 ms at a transmission
rate of 38.4 KBaud.

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Figure 9: IO-Link transmission frames

Why IO-Link
The Target use cases
The main target use is to give connectivity to devices which are not able to get a field bus connection and giving
these sensors and actuators enhancements and additional functionality like:-Precise analog value transmission in harsh environment
Replacement of analog 4..20mA interfaces
Parameterization of small devices (sensors and actuators)
Getting detailed diagnostic data
Monitoring of device conditions

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For the handling of devices in automation systems the use cases are-Remote access to devices for diagnosis
Fast and reliable device exchange without any tooling
Monitoring device data remotely

IO-Link functions to be supported
An integration of IO-Link into CIP shall support all main features and functionalities of IO-Link. This includes themapping and access to all supported data objects and services.
-Process data transmission (1 Bit to 32 Byte)
Service Data transmission (16 Bit index range)
Event handling
Direct parameter page support
System commands-Transmission of block parameters
Easy device exchange based on the identification of devices
Automatic device data exchange without tooling
Change from communication into SIO mode and vice versa.
Hot plug functionality

Tool integration (optional)
For a tool-based integration the interpretation of the device IODD shall be supported.

Specifications
IO-Link is a complete specification suite including “interface & system” as well as “test” and “device description.”
The specifications are divided into 3 documents (Figure 11).
-Interface and System
IODD (Schema, data representation in tools, parameter description
Test specification for masters as well as for devices for both Versions V1.0 and V1.1

Figure 11: IO-Link specifications

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The IO-Link technology is currently being standarized at IEC. The standardization process has reached the level
FDIS (Final Draft International Standard). The publication is expected in Q2 2013. IO-Link will become an IEC61131 standard. It is also integrated with PROFINET, EtherCAT, PROFIBUS, Interbus, and AS-Interface.
All specifications are fully publicly available via www.IO-link.com.

Summary
IO-Link technology is field bus independent and supports extended functionality improving machine performance.
The integration of IO-Link will enable user benefits for machine performance. IO-Link today is an approved
technology already integrated into a number of field buses. Many PLC suppliers are also supporting IO-Link in their
PLC modules and the appropriate engineering tools.

References
IEC 61131-9IO-Link.com**************************************************************************************The ideas, opinions, and recommendations expressed herein are intended to describe concepts of the author(s) for the possible use of CIP
Networks and do not reflect the ideas, opinions, and recommendation of ODVA per se. Because CIP Networks may be applied in many diverse
situations and in conjunction with products and systems from multiple vendors, the reader and those responsible for specifying CIP
Networks must determine for themselves the suitability and the suitability of ideas, opinions, and recommendations expressed herein for intended
use. Copyright ©2012 ODVA, Inc. All rights reserved. For permission to reproduce excerpts of this material, with appropriate attribution to theauthor(s), please contact ODVA on: TEL +1 734-975-8840 FAX +1 734-922-0027 EMAIL odva@odva.org WEB www.odva.org.
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