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SEMI E148: Time Synchronization

Posted by Cimetrix

Mar 18, 2010 8:31:00 AM

by Doug Rust,
Director, Product Engineering & Customer Support

time synchronizationThe time shift for daylight savings this week is going to cause me some grief for some time. Most countries in Europe will not adjust until March 28. Many countries in Asia (India, Singapore, Taiwan, Malaysia and Japan for example) are not adjusting for daylight savings at all in 2010. Since our customers are all over the world, I’m going to have a tough time keeping in sync. It’s inevitable that I’ll miss some important event this month. So, I thought it would be very àpropos to submit a blog about Time Synchronization.

SEMI® standard E148 defines software standards for the equipment communication interface to enable the equipment control computers to automatically synchronize their clocks from a standard time base. Although this standard was just published a couple years ago, it is not new technology. Computer systems have been using internet technology to synchronize their clocks with a common time base for over 20 years now. The Network Time Protocol (NTP – a.k.a RFC1305) is the internet standard for time synchronization that is designed to enable any computer to synchronize with a reference clock (most commonly the atomic clock in Colorado) through various time servers available on the internet. SEMI E148 specifies the NTP standard as the mechanism for synchronizing the equipment control computer with the factory computer systems (as well as some other requirements).

This is becoming a critical capability as factories begin to adopt other information technology that enables them to collect thousands of precise data points from each run on each tool. Making effective use of this data requires that the time-base for data source ‘A’ is the same as the time base for other data sources so that the raw data can be assimilated and correlated to produce valuable manufacturing information. If there was some important “event” in manufacturing that we need to analyze the first thing we will do is to try to determine what else was happening at the time of that event. So the first question we ask is “when did that occur?” That’s where we can run into serious problems if there is no common time base.

Most modern operating systems have the NTP client software built-in. It’s possible to synchronize with reliable time servers on the internet and there are many affordable commercial time servers available. Even if users do not implement all of the E148 requirements, I suspect we are going to see more and more factory networks using NTP to synchronize the manufacturing equipment with factory hosts over the next year (if they haven’t already done it). For me, I guess I’m going to be out of sync at least until May 28.

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Topics: SEMI Standards, SEMI, E148

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