STEP 7 and RSLogix5000

JesperMP said:

Both of these problems with shifting addresses are because you have absolute address priority.
Change to symbolic address priority.

edit:
And to the original question, I think there is very little that absolutely can be done in one platform and not in the other.

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I'm really hoping you're going to tell me that's a newer feature... I've eaten up weeks of time because of this!

bosko said:

I'm really hoping you're going to tell me that's a newer feature... I've eaten up weeks of time because of this!

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I am fairly certain that it was in 5.2.
(it is a small setting hidden fairly well. I struggled with exactly the same in the beginning).
You can learn from this that you must ALWAYS ask on plctalk first

I guess I am in the "nothing significant that only one can do" group.

Partial download vs. Online edits

Really two very different techniques to achieve the same end. So I think that should drop off the list of what either one can't do. They certainly cause people experienced in one system pain when moving from one system to the other, but they both get the job done in the hands of someone familiar with that system. And I'll go so far as to say niether system is well understood by a large segment of the users.

Addressing differences

I feel the same way, the approaches are different but they achieve the same ends. I can have a lot of control over the physical arrangement of tags in PLC memory in a ControlLogix if I choose to. Once again, if you are familiar with the system, you can make it do what you need.

Automatic type conversion.

This is a deliberate choice. Yes, they are different. But neither choice limits you in what you can do, merely how you do it.

mellis said:

I guess I am in the "nothing significant that only one can do" group.

Partial download vs. Online edits

Really two very different techniques to achieve the same end. So I think that should drop off the list of what either one can't do.

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Don't agree.

with Step 7 you can make the modifications before hand at your desk and simulate to test. then you can go to the live PLC and download the modified section. You may have to stop the process of you've changed DB length's etc, and download in a particular order. Quite often you can do a straight download without effecting the overall process.

With AB you would have to stop the PLC and download.


Another feature I like about Step 7 are the VAT tables.


I like the fact that the software is all built in with Step 7 and no license issues with older versions or part you need to connect to the PLC etc..

PeterW said:

Another feature I like about Step 7 are the VAT tables.

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They are called CDM (custom data monitors) in RSLogix.

One thing that S7/STEP7 cannot do:
Online Undo/Redo of edits. If your code turns out to be c**p, with the press of a button "untest" and can come back to before you messed things up.

Open a block from the online folder. Edit then download. If you are not happy then download the unmodified block from the offline folder.
Not the click of one-button though.

Not the same, you can edit in many program files, and then activate and deactivate the edits.
To do something similar in STEP7, you would have to have 2 projects, before and after you started editing. And then do the partial download. Much more cumbersome and error-prone, so much that I consider it a real major difference.

The CDM is only in RSL500, in 5000, there are watch windows, but you cannot save them (at least you could not the last time I worked with 5000.

Step 7 allows you to have pointers, RSL5000 does not.

Watch Windows can be saved starting with rev 18. By "pointers" are you referring to what RA calls "variable addressing"?

OG

Operaghost,

Can you describe variable addressing, its been a rev or two since I worked with RSL5000 and I have not heard the term?

Variable addressing has been with the Logix5000 system since Day 1. It is used to vary where in an array you are pointing. Typically an array is addressed with a fixed pointer such as MyStorageArray[3]. Element #3 in the array named MyStorageArray.

With variable addressing, you replace the fixed number inside the brackets with the name of a tag that is used to point to another location within the array. For example MyStorageArray[pointer] where the current value of the tag named "pointer" is used for the specific array element to be addressed. You could even use MyTagArray[pointer1+pointer2]. As the "pointer" tag changes, the logic points to a different array location.

Same idea as indirect addressing in the older PLC-5 and some SLC 500 but it does require the use of arrays.

OG

Siemens doesn't make you pay for support. (I.e techconnect)

nettogrisen said:

Siemens allows for greater address manipulability.

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Can you provide an example? I hear this bounced around a lot but with nothing to back it up.

nettogrisen said:

Siemens does not automatically convert datatypes. It gets really old, really fast when you have to convert INT -> REAL and back again etc.

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Personally, this is one of my biggest areas of frustration with Step7. Last project I did has volumes of code just doing silly INT/DINT/REAL/etc conversions. In this day and age it should be able to handle this by context. Unless one of the Siemens gurus can point out the way around this, I consider this a +1 for RSLogix.

jac said:

Both platforms have their advantages and the more I've had to do with Siemens the more I can appreciate some of the techniques that really save time.

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This is an example of where I was going with this thread. Can you please elaborate on the time saving techniques? Simply stating there are time saving techniques makes me think there is a box of secrets I'm not allowed to look into?

If I said I prefer RSLogix5000 because of all the techniques that really save time, what would be your resonse?

jac said:

But the kicker for me are strings and indirect addressing let alone indirect addressing on strings.

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I think this is a good example of a misunderstanding of capability. It isn't that you can't do these things, it is more so that you go about it a different way. I think Logix5000 abilities with with indirect addressing are actually quite powerful.

mellis said:

I guess I am in the "nothing significant that only one can do" group.

Partial download vs. Online edits

Really two very different techniques to achieve the same end. So I think that should drop off the list of what either one can't do. They certainly cause people experienced in one system pain when moving from one system to the other, but they both get the job done in the hands of someone familiar with that system. And I'll go so far as to say niether system is well understood by a large segment of the users.

Addressing differences

I feel the same way, the approaches are different but they achieve the same ends. I can have a lot of control over the physical arrangement of tags in PLC memory in a ControlLogix if I choose to. Once again, if you are familiar with the system, you can make it do what you need.

Click to expand...

Great viewpoint on this. I think you hit the nail on the head.

mellis said:

Automatic type conversion.

This is a deliberate choice. Yes, they are different. But neither choice limits you in what you can do, merely how you do it.

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This would be one I don't entirely agree with.
Deliberate? --Yes.
For good reason? ----- I'm skeptical.

Although it doesn't limit in capability, it can be a huge time waster.

If there are two ways to skin the cat, and they can both roughly be implemented within the same amount of time and code volume, I call it a draw.

If there are two ways of doing something and one requires a significant amount more expenditure of time and code, then I have to call that a +1 for one of the camps.