Tag Based Programming PLC

[jkerekes]

He may be refering to "Bit Overlays" See TN# 34380 - Bit overlays and RSLogix 5000 software. It's a way to give the individual bits of a UDT word their own tag name as well. Very useful in certain applications.

 

[TechEric]

A small PLC that uses tags in programming is this one: http://www.icpdas-usa.com/products.php?PID=454 . The tags are global or local (for individual functions you may write). External access to data is based on register offsets though, with Modbus TCP or RTU protocol.

 

[BobB]

The answer once again is yes. You just add 'sections', name them what you want (plant area) and write the code for that area in the named section.
I will place an image of comments and output comments when I have time - the output comments are really nice also.
All stored in the PLC and I still get my numbers - and everyone else gets there tag based stuff.
Oh, by the way, you also get tasks that can be turned on and off, ladder, FB, structured text and SFC as well as mnemonics. All bases covered.

 

[BobB]

Here are a few other things - not sure if all stored in the PLC or not.
Screen shot of rung comments and annotations.
Print out of rung comments and annotations.
Screen overview with sections in workspace on left. Can be named as plant areas - all ladder for the individual section is withinn the section.
Sneaky way of indexing a program to use the PLC software search function. Much better than searching for rungs etc - just put in some dummy outputs for the seach.
This does mean you need to have access to I/O numbers directly though but perhaps couls be applied to tag based. I will never find out if it can or cannot be done.
By the way, the rung anmnotations are really nice. Allows commenting of each output/function without having to find some way of doinmg it in the rung comment. Problem wityh that is you do not get the yellow numbers for reference.
Plenty more as well but have software, screens to write and commissioning tomorow morning.
Flash screens too.

 

[PdP]

Only AB, at this stage, makes provision for plant & process representation on a logical platform.

 

[PeterW]

Only AB, at this stage, makes provision for plant & process representation on a logical platform.

Explain?

Siemens historically has allowed for separating code into sub sections. others, such as AB are only just attempting to catch up.

 

[PdP]

It is obvious. Look at the structure & then look at the assignment of field logic. No further relationship to be established between logic and field once the data structure has been established and assigned. This even goes higher to the next level of control.

 

[GeoffC]

I think Peter's 'Explain?' was in regard to you stating that only AB can do this - When myself, BobB and others have named numerous other brands that allow "plant & process representation on a logical platform".

 

[Roy Matson]

Omron too - funny thing is I do not like tag based programming - too slow looking through a drop down list for the tag you want if many are similar. I would like to be able to turn it off.
I program using the I/O numbers directly, although I always have tag based available.

I don't pretend to know a fraction of what you system integrators do but as
an instrumentation guy working with DCS systems I am used to working with tags, I rejoiced when I struck my first RSLogix project. If you base the tags on some type of structure you don't have to search just type them straight in.
All the tags for pump P501 would start P501_ e.g. P501_ST, P501_SP, P501_FB
Interesting topic
Roy

 

[PeterW]

It is obvious. Look at the structure & then look at the assignment of field logic. No further relationship to be established between logic and field once the data structure has been established and assigned. This even goes higher to the next level of control.

When I started using PLC's back in the late 70's early 80's I was working with AB and IPC (later Honeywell). I remember programming a PLC3 and having a print out (using fan paper in those days) which measured 8 inches thick. One big program.

In 88 I started working for a company that used Siemens for the first time and was taken by the use of OB's, PB's and FB's and how this gave the ability to split a program into the machine functions.

This predated AB's ability by quite some years.

I am either not getting what you are talking about or you are talking nonsense.

 

[PdP]

Your not getting what I am talking about. I'll ignore the rest of your assumption. I understand the structure of logic and data within Siemens (S5 & S7) and Schneider (PL7-3, Unity Pro & Concept) products differs not a lot from Allen Bradley (ICOM, RSLogix,5 & 500), but in ControlLogix the physical plant equipment can be presented directly into an UDT (User defined tag) where the physical I/O can be directly assigned to that structure. This structure then forms a "template" for more others exactly similiar to the master. You then just populate them as needed, on any functionality/layout of the process/plant. If you need additional I/O for a valve, you change the master and then populate (Wonderware Archestra talks about "deployment" for their objects) this changed structure to all dependants. Easy and simple and very user friendly. You can then relate to the functionality of the equipment related to the process and plant layout, as all be similiar in definition. This is a powerful tool on PLC level from a DB layout perspective. Siemens with their DB structure, this can also be done, even with arrays, but the tagging is a problem to me. Maybe I am wrong.

 

[guchifosco]

Symbolic Addressing

Hi everybody. I like the "Symbolic Addressing" feature available in Siemens Step7 and Step7 MicroWin Software. It's very useful to me. I think it’s similar to the Switch to turn Tag based programming off, mentioned by BobB. Somebody know if there's a similar feature in UnityPro? I'm also wondering for a way to do "Search and Replace" work in the "Data Editor".
I've tried to export all the Variable list to Excel, doing all the "Search and Replace" work there and then importing back the list to Unity but doesn't work.

 

[GeoffC]

As explained earlier in the thread a true iec based system uses tag based addressing.
Not sure what you are trying to achieve with 'search and replace' question - but if you change a tag in the variable table that change is reflected throughout the program. So changing a tag name or any properties of that tag(address, comment, etc) are then changed wherever that tag is used within the program.
Note you can also get to the tag properties by right clicking on a tag within the program and selecting data properties

 

[GeoffC]

As far as export/import goes not sure by what you mean 'doesn't work'. I use this function extensively. I am guessing you exported a group of tags changed their names and imported. This will work but will create a whole new set of tags. If you leave the tag names alone and change any of the other properties and then import you will be presented with an option to replace the existing tags within the program - this will update those tags with the new properties.

 

[guchifosco]

Thanks for your answers GeoffC. I understand, but sometimes I have 10 machines with consecutives names, lice CTS1, CTS2, …, CTS10 and it’s useful to me to create all the variables associated to CTS1, then make copy and paste 9 times and do “Search and Replace” adding 1 in each instance in the addresses. I can achieve that in Siemens directly in Siemens software but I can’t in Unity Pro. I wish to have the option in Unity to switch off the Tag Based Programming, import my variable list in the program, then switch on the Tag Based Programming again.