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AS-I AS-INTERFACE OVERVIEW |
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AS-Interface – The Why and How of AS-i |
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What is AS-i, and why do I need it in my product? |
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AS-i nterface is an intelligent cabling system designed to replace the discrete wires that link a Programmable Controller with sensors and actuators. AS-i provides a single cable system that is fast, easy-to-wire and easy-to-operate. Built for the simplest types of devices, AS-i is a Master-Slave system where a single AS-i Master can exchange I/O data with up to 62 AS-i Slave devices. Each Slave can transfer up to four inputs and four outputs on a bus cycle.
AS-i is a standard hardware and software bus system that brings the reality of truly open systems to the lowest level of the automation business. Your customers are not just asking for connectivity at all levels of the control system, they absolutely expect and require it. Over 11,000,000 AS-i devices are now deployed worldwide. If you aren't already in this game, your competitors may already be a step ahead of you. |
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What is causing this enthusiasm for AS-I? |
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The first attraction to AS-i is its low cost. Cost savings are typically 15 to 40% of other bus systems using traditional cabling methods. Plus the ongoing additional benefits of a bus system ensure enhanced operation and improved maintenance which reduce life cycle costs while improving product quality because of better performance and less downtime.
Second, the sheer blazing speed of AS-i attracts a lot of attention. Connected slaves are polled in turn by the AS-i Master. A V1 network (31 devices) provides a maximum response time of 5mS per I/O point. In practice, most system have fewer than 31 devices and the cycle times can be significantly shorter. The newer, extended AS-i bus with 62 devices provides a maximum response time of 10msec per I/O point, still much faster than the data acquisition and logic scans of most Programmable Controller systems.
Thirdly, AS-i is inherently deterministic and repeatable. Transmissions between the master and slave are predefined and cyclic. The time to set an output is calculable with great accuracy.
And there are other attractions to AS-i including a simplicity not found in any other industrial network, device power right on the network cable and no need for Master or Slave Programming. There are no system parameters to set and devices are configured simply by identifying their device ID to the AS-i Master.
AS-i is a very important technology, not only because it addresses the lowest level of a control system architecture, but also because it is backed by Siemens, the worldwide leader in Industrial Control. This gives it an automatic advantage in the marketplace. AS-i will be successful for many of the same reasons that systems like DeviceNet have been successful; strong momentum and the backing of a vendor with a huge installed base. |
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