Ethernet protocol, EtherCAT, processes on the fly

EtherCAT processes Ethernet frames on the fly and maps through a Fieldbus Memory Management Unit (FMMU), distinguishing it from other industrial Ethernet protocols. One EtherCAT frame holds the data for many network devices, then...

09/01/2011


Industrial Ethernet protocols typically require individual Ethernet frames for each device on the network. Because of the Ethernet frame’s minimum length requirements as defined by IEEE 802.3, small payloads of a few bytes of data per node (typical for automation devices) results in poor bandwidth utilization. This means much of the communication is spent on overhead for the Ethernet packet, resulting in performance comparable to traditional legacy fieldbus systems.

EtherCAT’s general operating principle of “processing on the fly” for Ethernet frames, along with mapping through a Fieldbus Memory Management Unit (FMMU), distinguishes it from other industrial Ethernet protocols. One EtherCAT frame holds data for many network devices. The frame is not received and interpreted with the process data copied at each individual device. Rather, each EtherCAT slave device reads the data specifically addressed to it from the frame and inserts data into the frame while that frame passes through the node at full speed. Also, the frame’s cyclic redundancy check (CRC) is updated to reflect the new contents of the frame.

Simple integration of traditional fieldbus devices to EtherCAT is assured, including such networks as DeviceNet, Profibus, SERCOS, CANopen, and others. All data from these networks can be transmitted in the EtherCAT frame over a standard Ethernet cable. In this way, EtherCAT users can implement a gradual migration path, if necessary, to advanced industrial Ethernet. Data from other major industrial Ethernet protocols also can be transmitted over EtherCAT, including EtherNet/IP and Profinet. Besides industrial networks, EtherCAT can transmit all Ethernet Protocols: SECS, GEM, HSMS, TCP/IP, and so on. This is useful for communicating to standard TCP/IP devices, such as barcode readers, label printers, or human machine interface (HMI) screens via the EtherCAT backbone.

Other EtherCAT advantages over fieldbus systems include:

  • Very simple master and slave implementations - A synchronization method that sets the standard for determinism in industrial networks (distributed clocks)
  • Ability to implement any topology, including redundant rings and hot connect/disconnect segments, without the need for switches or any other active infrastructure components
  • Industry leading diagnostics with exact localization of faults for a variety of fault conditions
  • Lower costs than other industrial networks due to less expensive slave implementations, no infrastructure requirements, and no special master cards required.

- Joey Stubbs, PE, PMP, is North American representative, EtherCAT Technology Group. Edited by Mark T. Hoske, CFE Media, Control Engineering, www.controleng.com.

www.ethercat.org 

www.controleng.com/new-products/industrial-networks.html 

Industrial Ethernet: Application Optimization - webcast
Friday, October 7, 2011 at 2 p.m. ET/1 p.m. CT/11 a.m. PT (... and archived after that for viewing.)

http://www.controleng.com/media-library/webcasts.html 



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Your leaks start here: Take a disciplined approach with your hydraulic system; U.S. presence at Hannover Messe a rousing success
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
Inside IIoT: How technology, strategy can improve your operation; Dry media or web scrubber?; Six steps to design a PM program
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming
Managing automation upgrades, retrofits; Making technical, business sense; Ensuring network cyber security
Designing generator systems; Using online commissioning tools; Selective coordination best practices

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me