Standards defining industrial connectivity entering 2008

Industrial Embedded Systems — December 17, 2007

Primary Ethernet-based protocol standards

EtherNet/IP

EtherNet/IP was developed by Rockwell Automation Inc. and is maintained by the Open Device Vendors Association (ODVA). It uses TCP/IP for all communications and employs User Datagram Protocol frames for real-time communication. It implements Common Industrial Protocol (CIP) over Ethernet, so it essentially shares the same application layer as DeviceNet and ControlNet, the existing fieldbus protocols developed by Rockwell Automation Inc.

CIP Sync is an extension of EtherNet/IP, which employs the IEEE 1588 synchronization standard to provide real-time communication for synchronous control applications. CIP Motion is another extension of EtherNet/IP that supports motion applications.

ETHERNET Powerlink

ETHERNET Powerlink is an Ethernet-based communication protocol that provides hard real-time capabilities using 100 Mbps Ethernet and implementing scheduling mechanisms to provide deterministic access. It was introduced in November 2001 by Austrian company Bernecker & Rainer Industrie-Elektronik GmbH (B&R) and is managed by the ETHERNET Powerlink Standardization Group. Initial members of this group include Hirschmann Automation and Control GmbH, Kuka Roboter GmbH, Lenze AG, B&R, and Zurich University of Applied Sciences.

ETHERNET Powerlink Specification V2.0 was released in late 2003. This version added Application Layer Device Profiles based on the CANopen protocol developed by the CAN in Automation (CiA) organization.

PROFINET

PROFINET was developed by Siemens AG and is maintained by the PROFIBUS International organization. It is an extension of PROFIBUS DP, which is designed to work over Ethernet, and has the same application layer and compatible Device Profiles.

PROFINET currently provides three levels of performance:

n   PROFINET V1 (non-real-time) provides a response time of 10-100 ms using standard Ethernet components

n   PROFINET RT provides a response time of 5-10 ms using a software solution based on standard Ethernet components and a dedicated TCP/IP channel to provide soft real-time capability

n   PROFINET Isochronous Real-Time (IRT) uses dedicated hardware on the Ethernet interface to provide a response time of less than 1 ms with 1 ms jitter

The PROFINET standard is closely controlled by Siemens AG and the PROFIBUS International group.

EtherCAT

Ethernet for Control Automation Technology (EtherCAT) is a master/slave protocol originally developed by Beckhoff. EtherCAT provides a hard real-time capability using dedicated hardware on the slave nodes. An EtherCAT network typically uses an open ring topology. An Ethernet frame transmitted by a master can contain multiple commands. When a slave receives a frame, it processes it in hardware to retrieve or insert information and then forwards it on to the next slave in the ring. Hardware processing adds a delay in nanoseconds. This protocol provides one of the best performances in terms of response time and jitter, but does require dedicated hardware to be implemented on each slave device.

IEEE 1588

IEEE 1588 is not a communications protocol; it actually describes a method for synchronizing the local clocks on multiple remote nodes on an Ethernet network. It addresses the requirements of applications where real-time or hard real-time communication is needed. These can include motion control, industrial automation (network switches and controllers), and a range of test and measurement applications.

IEEE 1588 has been adopted by communications protocols such as PROFINET and EtherNet/IP and is being considered for ETHERNET Powerlink in hard real-time applications.

While Ethernet is making rapid inroads in these areas, the interface and backward compatibility to existing systems are still vital to organic growth. The wide range of protocol support can enable gateways between Ethernet-based systems, such as separating public and private data streams provided through CAN, Ethernet, or proprietary protocols.

SERCOS III

SERCOS III is an evaluation of the original Serial Real-time Communications System to be used with Ethernet-based networks. Rather than being bolted on top of the typical TCP/IP framework, the SERCOS III protocol has been used as the basis with the TCP/IP framework bolted onto it, resulting in SERCOS III remaining a deterministic method of controlling drives.

Fieldbus technologies

PROFIBUS

PROFIBUS is a fieldbus standard developed in 1989 by a consortium of German companies led by Siemens AG. Now the most widely used fieldbus in Europe, PROFIBUS was specifically designed to provide high-speed communications between I/O devices in factory and building automation applications. The PROFIBUS standard is maintained by the PROFIBUS International organization, and its main technologies are covered in the IEC 61158 and IEC 61784 standards.

PROFIBUS Decentralized Periphery (DP) describes communications between a central controller and distributed I/O devices. It is a master/slave protocol and can use a number of transmission technologies. Typically, it operates over an RS-485 network, using twisted shielded pair and a selectable bit rate up to 12 Mbps. PROFIBUS DP is divided into three versions: DP-V0 provides basic functionality, cyclic data exchange, and diagnostics; DP-V1 provides support for process automation; and DP-V2 provides several enhancements primarily aimed at supporting drive technology.

CAN

Ethernet is still not suitable for virtually all industrial applications. For example, the CAN protocol still has a strong position in environmentally challenging areas. CANís continued popularity is especially evident in industries adopting the requirement to maintain 100 percent data integrity, such as print media factories and semiconductor manufacturers. Because of its data integrity benefits, CAN is also starting to expand outside the traditional industrial areas to include bank terminals and medical equipment. In addition, CAN is widely used in automotive networks.

IEA 709.1 LonWorks

The LonTalk protocol, developed by Echelon Corporation as part of its LonWorks platform for network communications, has been incorporated as an international standard ANSI/EIA/CEA 709.1. The LonWorks platform comprises a number of elements, including the LonTalk protocol, transceivers, and microprocessors. Typically, LonTalk runs over twisted pair or powerline, and transceivers exist to support both.

The FTT-10A Free Topology twisted pair transceiver has been available for more than 10 years. However, Echelon is now providing smart powerline and twisted-pair transceivers that integrate the physical transceiver with the Neuron chip. Work is ongoing to develop Lon over Ethernet. Example applications for LonWorks include building control, HVAC, braking control on trains, and municipal street lighting.

BACnet

Building Automation and Control network (BACnet) is a communications protocol standard developed specifically to meet the needs of building automation and control networks. Developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), BACnet is currently defined in ASHRAEís standard 135.

BACnet can operate over a variety of network technologies, including Ethernet, ARCNET, or a master/slave token-passing network for lower-speed requirements. BACnet can even operate using the LonTalk protocol. However, the higher-level control languages for BACnet and LonWorks are not compatible. Applications for BACnet include HVAC control, fire detection and alarms, lighting control, and security. BACnet is now approved as ISO standard 16484-5 and designed to work at the management (backbone) and automation levels.

KNX

KNX, a building automation protocol administered by Konnex Association, is the result of convergence between the European Installation Bus, Batibus, and European Home System standards. It is approved as European standard CENELEC EN50090 and ISO 14543. It can use powerline (similar to X10 type communication), twisted pair, Ethernet, or RF as the physical layer interface. KNX is predominantly used in Germany, with by far the largest proportion of partners based in Germany.

Bruno Baylac is director of marketing for Freescale based in Toulouse, France, covering microcontrollers, digital signal controllers, analog, sensors,  and low-power radio products in the consumer and industrial markets in Europe, Middle East, and Africa (EMEA). Brunoís first position with Motorola was European program manager for Seamless Silicon Systems (S3), based in Munich, Germany. In 2000, he became operations manager for the emerging business portion of the Body Electronics & Occupant Safety Division, during which time he played a key role in the launch of Motorolaís first microcontroller + RF and remote keyless entry solution. Bruno also served as strategic marketing manager and global OEM market operations manager for the 8/16-bit Products Division.

Gordon Padkin is a product marketing engineer for Freescale based in the East Kilbride facility in Scotland, working in the Consumer & Industrial Operation in EMEA primarily focusing on the microcontroller portfolio for consumer and industrial markets. Since joining Freescale in 1999, Gordon has worked in several areas ranging from marketing research in the automotive chassis market to product marketing and management for the legacy 32-bit 68K and M.Core products as well as the new 32-bit ColdFire family.

Freescale Semiconductor

Bruno.Baylac@freescale.com

Gordon.Padkin@freescale.com

www.freescale.com