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Old February 12th, 2005, 06:32 PM   #1
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Flags, Tags, industry terminology and acronyms.

Please excuse me I forgot my password..its at work I am BOWRIDER.I have been a regular visitor to this site for some time now. I am a lowly maintenance mechanic who has been in the process learning plcs on my own for some time now. It was this site that inspired me on the solution for a problem we had for a certain piece of equipment. Forgive me for not remembering the contributor but he posted an example of indirect addressing to get into the guts of how a timer works (Allen Bradley). We had a problem with a case erector seeming to loose “time” intermittently and not releasing the cases when it was supposed to. It is controlled by a micrologix 1000. Using the contributors example, (I had to use indexed addressing since the 1000 does not support indirect), I created a “trap”. Basically I took a snapshot of the high speed counter every 10th of a second or so and when the machine screwed up again I checked the log and found the counter had actually reversed and stalled and then took off again. The cause turned out to be the coupling between the encoder and the drive had split and occasionally was breaking loose and slipping. Because of the mount position of the coupling you would have never seen it. So hats off to all of you for your past, present and future help.
Now my question I have had a problem with the terms Flags, Tags and some acronyms used on this site. DDE, DINT? And many more. I would love to see a layman’s (translate stupid guys) explanation. From what I have gathered the term flag could represent any (my term here) internal bit. Tags. Another word for an address? I would most welcome your enlightenment.
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Old February 12th, 2005, 08:55 PM   #2
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A 'Tag' is generally a full description type reference for a location within a PLC of such a nature that it can/must be used instead of the purely technical description. You may have noticed some in the documentationfor you Micrologix 1000. For example, the location N7:10 may also have a name 'Production_Target'. This name may directly be used when referencing the location N7:10. In the ControlLogix platform there are ONLY tags. The compiler keeps the actual location to itself. In some cases PLC and Display Terminal software may cooperate by using a common 'tagbase' of locations. Hope this helps.
Controlling outputs is the PLC's way of getting its inputs to change.
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Old February 12th, 2005, 10:08 PM   #3
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A "flag" is a bit that has some special significance. For example, after some long data-crunching operation a special bit may be set in order to indicate to the other parts of the program that the data has been crunched. Most people would call it "complete", or "done" flag.

DDE = Dynamic Data Exchange. The oldest Microsoft way to allow one Windows program to talk to another and to share data. Values from Excel spreadsheet may be reported into a Word file etc. As far as controls systems go, DDE is still widely used to present values from a program that can talk directly to a PLC (like a communications server) to the aforementioned Excel spreadsheet. There are several other ways of doing the same thing now, faster and more advanced, but DDE is still pretty much alive.

DINT = Double Integer. The name of 32-bit long data type in some PLC systems. Some other would call it Long, although there might be some disagreement on which one is treated as always positive (unsigned) value, which one may have a sign, or if they are exactly the same. Using a DINT means taking any two sequential 16-bit PLC registers (or words, or INTegers) together and treating them as one "double-length" register, in order to be able to work with really huge numbers.

Feel free to ask more.
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Old February 12th, 2005, 11:29 PM   #4
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God bless you, son, for trying to improve on your knowledge of this crazy field we're in. don't sell yourself short, i.e. "lowly maintenance man". there are many of us here that wear the same hat that you do. i'm impressed with anyone that wants to learn and asks questions that may seem "stupid" to the gurus, but are important nonetheless if you don't know the answer to them.
i've been in industrial maintenance for 35 years or so, a relic from the old relay logic days, when it took a 6 ft. tall by 9 ft. wide cabinet to hold all the components and wiring to run 2 100 hp. compressors alternately. that same job can be done today with a micrologix and a few other components you could fit into 24" x 24" panel. if you need any advice or training materials, please e-mail me, and i'll be happy to send you what i have on disk, or copy some of my older stuff and send it to you as an attachment.
good luck with your "kaizen", (striving for perfection, or something like that).

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Old February 13th, 2005, 04:46 AM   #5
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I am a lowly maintenance mechanic
Do noy underate yourself with this type of terminology. Many of us started ther.

A flag basically is a bit. Depends who you talk to. I will post a list of IEC type addresses tomorrow for you. It may be of some help in understanding IEC terminolgy regarding bit and word addresses.
The Old Pfhaart

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Old February 13th, 2005, 08:22 AM   #6
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Flags tags and other acromyms.

Sure am glad he asked this question. Been wondrin myself. Did not know enough to enable me to ask the question in an intelligent manner.

Lowly mechanic ???
Well at least they pay you.

A lowly student

Dan Bentler
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Old February 16th, 2005, 03:09 PM   #7
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Thank you all for your answers to my query. Once again exactly the information I was looking for. The “tag” description pretty much fit the bill from what I observed in you posts as well as my own observations of programs at work. The “flag” description also pretty much fits in. It is not a special type of bit or address, just one the carries an important or special function? Correct?. The terms DDE and DINT, are eye openers also. I would ask you all to please be patient with me because I intend to be much more free with my questions from now on. Up until now I have been shy I guess, not anymore. You all are so free to help and this speeds up my knowledge gaining factor by about 1000% as opposed to trial, error and downright guessin!
Thanks again.
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Old February 16th, 2005, 03:59 PM   #8
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Apologies. Forgot to get back with some details. Really busy.

Here are some typical IEC type addresses

BOOL - bit address
WORD - word address (16 bit)
DWORD - double word address (32 bit)
LWORD - long word address (64 bit)
INT - signed integer (16 bit) - most significant bit is the sign - (1 = -, 0 = +)
UINT - unsigned integer (16 bit)
DINT - signed double integer (32 bit) - most significant bit is the sign - (1 = -, 0 = +)
UDINT - unsigned double integer (32 bit)
LINT - long signed integer (64 bit) - most significant bit is the sign - (1 = -, 0 = +)
ULINT - long unsigned integer (64 bit)
UINT-BCD - unsigned integer BCD (16 bit - 0-9999)
UDINT-BCD - unsigned double integer BCD (32 bit - 0-99999999)
ULINT-BCD - unsigned long integer BCD (64 bit - 0-999999999999)
REAL - 32 bit floating point maths (IEC format) most significant bit is sign, next 8 bits are exponant, remaining 23 bits are mantissa with an assumed 1.0
LREAL - 64 bit floating point maths (IEC format)

Hope this helps.
The Old Pfhaart

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