Industry News, Trends and Technology, and Standards Updates

SECS/GEM Communication & Parenting

by Brian Rubow,
Principal Engineer

He Said…No I Didn’t
SECS/GEM Communication I have a lot of children—seven. Many of them are still young. Sure it is a lot of fun. However, more often than I like (yet not terribly often since I have really good kids), I get caught in the middle of a “he said/no I didn’t” dispute. That is where one of my children shows up in a huff to wherever I am and reports what “he said”, he meaning another one of my children. Then in the background I’ll hear the other one say either the “no I didn’t’ or the “but that’s because he said” response. And both kids look at me and expect the impartial judge (a.k.a. me) to do something. Each of them will give the impression of complete honesty and full recollection, yet they cannot agree about what happened or about what the other said.

My preference is to make them work it out. Still, I can’t help but wish that I could have recorded what actually happened so that if one of them is being a poop I can apply fair discipline. It would be really nice to attach a recording device to each of my children 24/7 to see what really happens. Would that be considered cruel or responsible parenting? Probably depends on whether you are the parent or child.

At Cimetrix, we deal with similar situations working with SECS/GEM communication. Sometimes either the host or equipment reports a problem. The host software says “the equipment said” and the equipment software says “but the host said”. And both look to an expert like me and want a resolution.

Often the best way to resolve the problem is to look at communication log files. Often enough when such problems occur the first time, neither the host nor the equipment was logging the SECS/GEM communication. Sometimes turning on communication logging in the host or equipment is more difficult than it should be. In a few cases, the host or equipment logging might not be trustworthy. The best solution is an impartial judge that records what both the host and equipment are saying so as to not rely on the host or equipment software.

But can that be done? The answer is yes. There is a free product called WireShark available on the internet at It is a network protocol analyzer, also called a “network sniffer”. It is really cool because it can capture all messages sent by the host and by the equipment without any modification to the host or equipment. Just configure it and run the problem scenario again.

Only it is not quite that easy. One problem is that WireShark does not have a plug-in to interpret the binary SECS/GEM message format (HSMS). If you are a SECS/GEM/HSMS guru that can readily and quickly interpret SECS/GEM messages in hexadecimal format, then this is a minor inconvenience. But for most of us that are too busy for such a tedious task, this is a major problem that makes WireShark impractical.

Fortunately, Cimetrix has a new product to resolve this, CIMSniffer. Under the hood, it uses the same network capturing libraries as WireShark, yet it has the capability to convert the messages into human readable SML formatted messages. You don’t have to wonder exactly what “the equipment said” or what “the host said”. You can record what they said yourself using a third-party software application. I wish I had this years ago. Too bad it won’t work with my kids.

For more information regarding the CIMSniffer product, please email

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Topics: SECS/GEM

Posted by Brian Rubow: Director of Solutions Engineering on Nov 18, 2009 1:16:00 PM
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