STEP 7 and RSLogix5000

DamianInRochester · Nov 12, 2011

PeterW said:
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.

I have never tried that with Step7. Unless someone can correct me I would have to give that a +1.

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

RSLogix5000 has the equivalent.

PeterW said:
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..

I don't think this is true in general, but on average I agree that Rockwell is much worse when it comes to this sort of thing. At the same time, I can't view this as a matter of capability although it is a good point.

DamianInRochester · Nov 12, 2011

JesperMP said:
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.

I have to agree with Jesper on this one, even though I never use this feature myself I would have to say it is significant enough to count.

DamianInRochester · Nov 12, 2011

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

Very valid point. In my top 3 irritants with Rockwell is the fact that they hold some of their technotes under lock and key unless you have a support contract. That is just so wrong on so many levels.

However, that has nothing to do with functionality.

DamianInRochester · Nov 12, 2011

And thanks to everyone for your 2 cents!

infineum · Nov 12, 2011

Lots of differences

There are many functional differences between the two. RSlogix 5000 offers many advantages over step 7

In step 7 you cannot build a plant hierarchy. Only offered in PCS7 Therefore you cannot build folders based on how you plant is constructed. For example, I have a reactor with a heat/cool loop, stirrer, vacuum pump etc. I can build a hiearchy in logix based on how the systems work together; the heat/cool loop code under the reactor, etc. In step 7, you have a bunch of block folders.
SFC is not offered with step 7 just PCS7. Step 7 does have S7 Graph which is poor.
Step 7 does not offer any S88 functionality; phase logic, phase manager etc.
Step 7 function block language is an optional package CFC. The FDB feature in step 7 is not equivalent to logix function blocks. Once you use CFC, it is real difficult to write programs in LAD, STL, or IL unless you compile these blocks into CFC.
Logix does not offer IL for those who like to program in this manner.
Step 7 uses OBs for periodic tasks, fault routines, etc. There are dedicated blocks for faults such as OB85. They are very powerful but you must understand how they work or you can encounter issues. More programming is required for the same functionality in Logix.
There is no good shift register function in step 7. You can program a large shift register in Step 7 but it is not easy. Logix is superior in this regard.
The message block is logix is much simpler than Step 7 Send/Receive. In addition, ethernet communications must be set up in NetPro which is not to0 easy to use.
Logix is much better integrated to drives and in general offers better integration with RSLinx. Siemens has starter, Netpro, hardware config, and simatic net. They all work but not as simple or seamless as Logix. This is my opinion.

Genchan · Nov 12, 2011

Address priority on S7

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

This is right.
I have created a project with symbolic addressing. Once I change a symbol in DB, "Check block consistency" is need and so many blocks are re-compiled. This is terrible. Furthermore, if S7-Graph block has some warnings like "empty transition", each of them warns programmer of this. You will have to remove the reason or hit "OK" for each block.
I think symbolic addressing is very useful but slowly on Step7.

PeterW · Nov 12, 2011

infineum said:
There are many functional differences between the two. RSlogix 5000 offers many advantages over step 7

In step 7 you cannot build a plant hierarchy. Only offered in PCS7 Therefore you cannot build folders based on how you plant is constructed. For example, I have a reactor with a heat/cool loop, stirrer, vacuum pump etc. I can build a hiearchy in logix based on how the systems work together; the heat/cool loop code under the reactor, etc. In step 7, you have a bunch of block folders.

Unsure what you mean here, Siemens were miles ahead of any other PLC with this, the fact that you could separate areas of plant when you wrote the code, in the structure you designed in the areas.

Usually I would create FC's for specific areas and call these in OB1 which is just a distribution block.

Within the FC's I would call FC's and FB's for an area of plant.

The fact that you can share IDB's and call FB's from within FB's (either in STAT area's or with UC's) means you can link all blocks for an area in plant together quite easily.

PeterW · Nov 12, 2011

Genchan said:
This is right.
I have created a project with symbolic addressing. Once I change a symbol in DB, "Check block consistency" is need and so many blocks are re-compiled. This is terrible.

I think you mis-spelt 'very good'.

This feature means you can modify and add/remove things in thei FB STAT areas without the need to manually re-address in blocks.

Genchan · Nov 12, 2011

PeterW said:
I think you mis-spelt 'very good'.

This feature means you can modify and add/remove things in thei FB STAT areas without the need to manually re-address in blocks.

Thank you for your reply.

I think you wrote about "function" of Step7. I also think this function is good as you wrote. But I want to point "this is too slowly for me". So I wrote it "terrible". How do you think about time for consistency check?

JesperMP · Nov 12, 2011

Does ControlLogix have an onboard webserver ?
S7 PN CPUs do, and I think this is really nifty. It gives you access to the diagnostics without having to have STEP7. You can add VAT tables, and even your own web pages. I am experimenting with it at the moment.

About the differences in online download of blocks, and multiple edits deactivating and activating:
The functionality is similar and different at the same time.
The similarity is that you can do multiple edits in many places and then activate them at once, and you can undo the edits if you wish to.
The difference is that Siemens style is to make a lot of modifications offline, and you download them all in one go. Whereas Rockwell style is doing many small edits online and testing them in small increments.

Operaghost · Nov 13, 2011

Ok, this is a bit OT, but I have to respond to this:

DamianInRochester said:
Very valid point. In my top 3 irritants with Rockwell is the fact that they hold some of their technotes under lock and key unless you have a support contract. That is just so wrong on so many levels.

However, that has nothing to do with functionality.

I think it is only fair to point out a couple items:

Siemens has 405,000 employees
30,000 of which are strictly R&D
Siemens had revenue of ~$76B in 2010
Industry Sales accounted for nearly 1/2 their employees and revenue

Rockwell has 21,000 employees
Rockwell had revenue of $6B in 2010

We sometimes think of them as equals, particularly with the popularity of RA here in the States, but Rockwell is actually one of the smallest manufacturers among their peers. They can't fall back on Automotive, Medical or Energy for profits. They make everything from Automation alone.

OG

DamianInRochester · Nov 13, 2011

Operaghost said:
Ok, this is a bit OT, but I have to respond to this:

I think it is only fair to point out a couple items:

Siemens has 405,000 employees
30,000 of which are strictly R&D
Siemens had revenue of ~$76B in 2010
Industry Sales accounted for nearly 1/2 their employees and revenue

Rockwell has 21,000 employees
Rockwell had revenue of $6B in 2010

We sometimes think of them as equals, particularly with the popularity of RA here in the States, but Rockwell is actually one of the smallest manufacturers among their peers. They can't fall back on Automotive, Medical or Energy for profits. They make everything from Automation alone.

OG

OG,
What is your source for these numbers?

Even taking those numbers at face value, you have just demonostrated how a much larger company doesn't charge for support. This has always been the rationale people have given for why Rockwell has to do stuff like this, not the other way around.

I can now rattle off thousands upon thousands who are much smaller than Rockwell that don't either.

In truth, there really are not a lot of them out there that do. Rockwell decided to take the Microsoft route.

Company size has got nothing to with it. If anything they should have better ecomony of scale than most.

I completely refute the notion that they make everything off of automotive alone as well.

If your trying to make the case that Rockwell is under such financial duress that they need to charge for (technotes) information that should be publically available I would much sooner assert that the reason Rockwell may be struggling now is because they do things like this in the first place.

All that being said, the last place I wanted this thread to go wash a bash of Rockwell or Siemens. There are many things that irritate me about Siemens as well.

infineum · Nov 13, 2011

I have used both Siemens and Rockwell support. Siemens support is free if you are using currently supported products. If you are using a mature product support is not free.
Logix is native with ControlNet, DeviceNet, and Ethernet I/P. Step 7 is native with Profibus, Profinet, and ASI.
When I refer to plant hierarchy, I mean how a project is built in either Step 7 or RSLogix. You can build a hierarchy is code, Logix and PCS7 using the Plant View allow you to build the project based on your plant layout using folders. It is a great help when troubleshooting a project that you are no familier with or having worked on in a while.
Logix does use a webserver with its ethernet cards in controllogix. The inboard ethernet port in CompactLogix might offer a webserver but I am not sure. The newer Siemens PN controllers do offer dual ethernet ports that support a ring structure. Controllogix has card with dual ports but compactlogix does not.

Operaghost · Nov 13, 2011

DamianInRochester said:
OG,
What is your source for these numbers?

I don't want to hijack this topic so I will let your comments go (Automotive? Really? That's not close to what I said). But as for my numbers.......

Siemens 2010 Annual Report (http://www.siemens.com)
Click Investor Relations. Siemens announced their 2011 results last week but I have not had a chance to digest their numbers yet.

Rockwell's web site (http://www.rockwellautomation.com)
Click "About Us" and you'll see the numbers right there.. RA also just announced their earnings last week.

Sorry, for the OT, I will stick to on topic now I promise

OG

DamianInRochester · Nov 13, 2011

Operaghost said:
(Automotive? Really? That's not close to what I said).
OG

Sorry, I do need my eyes checked!

And thank you for pointing to the numbers.

Operaghost said:
Sorry, for the OT, I will stick to on topic now I promise

OG

Apology not accepted. You have nothing to applogize for. Please accept my appology if I came across that way. If you feel I was off base by my comment about withholding tech notes please feel free to point out why. My point is, there are many other companies out their that rely solely on Automation for their revenue that do not find it necessary to make you pay for things like that.

STEP 7 and RSLogix5000

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