Industrial Ethernet continues to find wider adoption in automation systems

According to a recent report from IMS Research, there were more than 30million networked nodes in industry, with 23.2% of them using a variant of Ethernet. These figures are predicted to increase by 2015 to 26.2% and 45.1m nodes respectively. Yet while Ethernet is making inroads, it isn't achieving a dominant position. The interesting word in the IMS report is 'variant'. Since the emergence of fieldbus technologies in the early 1980s, the sector has been typified by a blend of proprietary protocols and 'flavours' of Ethernet. While the report says the dominant industrial Ethernet technology is TCP/IP, it lists another seven variants before it gets to the inevitable 'other' category. The reason? Many controllers still require the use of a particular protocol – the concept of open architectures remains an unachieved goal. Gavin Stoppel, applications manager with Harting's Smart Networks Infrastructure Product group, says: "Ethernet is making itself the de facto standard for a lot of industrial communications." But he also noted that Ethernet brings with it the need for higher quality components. "There is a growth in demand for resilient networks in the industrial automation environment and reliability is one of the biggest requirements. That's about making sure there are high-quality connections; even the basic RJ45 connector needs to be of high quality. Then there's Ethernet shielded cable and the devices themselves." Stoppel sees a merging of communications environments from the office through to the factory. So too does Dr Wiren Perera, VP corporate strategic marketing and LAN solutions. "Industrial Ethernet has been used in corporate networks for some time, but it's moving towards the shop floor," he said. "They have chosen a standard means of communication because more important data is being transferred from one environment to the other. The communication has to be seamless, so companies such as Harting are now looking at developing products that start to manage data." Harting has developed Fast Track Switching as a means of supporting all protocols based on Ethernet. According to the company, the switching method ensures that all performance and determinism requirements are met. "Fast Track can recognise the different protocols in use," Stoppel noted, "and give them priority over standard Ethernet messages. This gives more control over latency and allows the product to meet the requirements of an automation network." Fast Track has a three-step approach to networking. In step one, automation frames are detected based on the header information in the Ethernet frame. The next step is acceleration. Harting says that, unlike 'store and forward' approaches, the complete frame does not need to enter the switch's memory. Once an automation frame is detected, cut-through switching technology forwards the frame to the appropriate output port. Detected automation frames are always given preference, which makes sure that IT frames always have to yield to automation frames. Once the automation frame has been sent, the IT frame is resent. Harting claims these mechanisms guarantee the levels of determinism and performance required by automation systems. He believes it's an approach that makes Ethernet more flexible in the industrial environment. "There are different degrees of resilience," he offered. "You won't find an exclusive Profinet network, for example; there will be a mixture of protocols. That means the devices need to be able to switch themselves and for them to be capable of handling and transmitting data without extended latency." Micrel's Dr Perera is particularly interested in latency and pointed to the company's recently launched KSZ846x range. These devices use Micrel's EtherSynch technology, which integrates IEEE1588v2 distribution synchronisation, Ethernet switching and precision general purpose I/O. "IEEE1588 allows you to string devices together," he explained, "and to synchronise them to allow for time delays." Micrel says EtherSynch technology combines Ethernet communications, IEEE1588v2 distributed synchronisation and precision general purpose I/O in an integrated, energy efficient solution. The synchronisation and communications processing abilities offload the host cpu, while the general purpose I/O allows locally connected devices to take advantage of synchronisation. KSZ846x parts are suitable for use with cpus which don't feature an Ethernet MAC." Micrel says the parts can be used in distributed networks and adds the architecture reduces the synchronisation and communications processing load on system CPUs. "By integrating IEEE1588 time stamping as close to the physical layer as possible," Dr Perera noted, "synchronisation performance of less than 100ns has been demonstrated. In fact, we've shown jitter of less than 58ns. "It's a cost-effective solution for implementing industrial Ethernet networks which reduces size and power consumption when compared with fpga based designs. A high level of integration reduces costs, making IEEE 1588v2/Ethernet a viable contender for FieldBus applications by replacing point to point serial interconnects." Stefano Zammatio, product manager with Altera Europe, says: "We see [industrial networking] moving towards industrial Ethernet, but the progress hasn't been as swift as was predicted. Even so, it is getting there slowly." One of the attractions of industrial Ethernet for Altera is the fact the technology continues to evolve. "This makes it ideal for FPGAs," Zammatio claimed. "When Altera first started looking at the market, there were a range of vendors offering particular features. Since then, most of them are offering additional functionality – redundancy, for example. This makes the market hard to approach from an asic perspective and this will continue." Zammatio sees vendors still being aggressive in what they are looking to achieve. "All are open to adding new features but, because the market is not 90% industrial Ethernet, fpga designs with new features can be turned round quickly. But our challenge is dealing with multiple vendors and that's why we've started working with Softing." In partnership with Softing, a leading supplier of Industrial Ethernet protocols, Altera can offer an FPGA with an integrated software stack that is said to provide an easy and inexpensive way to develop industrial Ethernet and fieldbus connectivity platforms. Harting, meanwhile, is still looking at IEEE1588. "However," Stoppel noted, "while we realise that timing is becoming a more important issue, we don't think that certain protocols have got to that level as yet. The standard has been around for some time, but has yet to be implemented widely by automation manufacturers." Stoppel added that, from a real time control point of view, there is a move towards protocols that support real time messaging. "Profinet IRT – isoschronous real time – is one such protocol," he pointed out. "Harting isn't tying itself to a particulary protocol, rather it's developing devices which have multiprotocol capability and customising them." Concluding, Dr Perera said: "System builders often have a lot of problems when building systems. We are making it easier for them."