PCS7 -- The Pros and Cons


Thread Starter

Bryan Kowalchuk

For all experienced users of PCS7, what would you say are the biggest pros and cons with PCS7?

I've heard that the WinCC software portion has a tendency to crash alot, that the scripting is limited to 64K total for all scripts, that a number of errors that show up after performing an illegal action are still in german, and that
technical support is poor.

From the Step7 perspective, from the little I've seen, the SFC portion seems limited by the number of transition conditions that are allowed, without of course getting fancy and grouping conditions in a separate section of code. The
CFB portion of it looks like it can easily become unruly. I like the idea of being about to create device/object blocks, like those seen in APT, but with the added feature of being able to tailor their functionality to what the project requires. One of the biggest issues I see, with S7 in general, is the general inability to make online changes without interrupting and usually
stopping the processor. In a process where a momentary shutdown requires a lengthy CIP, this is certainly not desirable.

If you have any major issues that you are willing to provide, that would be greatly appreciated.


Donald Pittendrigh

Hi All

Please explain under what circumstances you have to re-start your S7 to do program changes. I have commissioned several S7 400's and 300's and I don't understand why this is neccessary, or perhaps you are having this problem with the S7200 range. If this is the case you should please be more carefull about this type of generalisation, the S7200 is neither programmed the same way nor operates in the same way as the other 2 and is really not possible to compare to PCS7!!!!!!!!!

Donald Pittendrigh

Bryan Kowalchuk


Thankyou for your feedback.

Keep in mind that some of the information I provided, in reference to PCS7, is second hand.
I've had a limited amount of experience with S7 (S7 318s) on its own, and, with the exception of making hardware modifications, which I don't believe you can do without stopping the PLC, I suppose your right. What I'm not at all familiar with though, and maybe you are, is the use of SFC's and CFC's in the extended packages found in PCS7. Do you know if there is anything that prevents you from downloading, for example, modifications to an SFC without having the PLC stop. If so, then a process type project would not be a great application in which to use SFC's, etc.

I appreciate your feedback.

Bryan Kowalchuk

Ronald Nijssen

You can download SFC (Sequential Function Charts) and CFC (Continuous Function Charts) on-line. However, PCS 7 allows you to define your own
Control Blocks with code, data and an Interface, if you change the interface of such a block, and it is used in CFC, then on-line download is not
allowed. Please keep in mind, changes to these blocks, which are used as typicals, is not commonly done in a running plant. You can add, remove and change block interconnections and calls and download on-line

Kind Regards
Ronald Nijssen

Jeff Winborn

I'm a former Siemens applications engineer with extensive PCS7 experience. It's true that certain changes will require the plc to go to stop. Changing the hardware configuration is the most common. In CFC, updating a function block (unless the change is to the source code only) will require compiling/downloading the entire program. In SFC, if the SFC that was changed is also active, then the SFC must be put in manual mode and stopped before downloading (the plc remains in run). If you have any questions, I'll do my best to answer them.

Jeff Winborn
Industrial Systems Design
(423) 282-6088
[email protected]

david mertens

The statement that you have to stop the PLC is not allways true as most changes to CFC's or SFC's can be loaded on-line. The situation where
you create your own blocks in SCL or STL (This is the APT equivalent you reffered to) may require a complete download (with PLC in stop) if a change is made to the interface of the blocks. Also a change in the hardware configuration requires that the PLC be put in stop. However this does not mean that the installation should be stopped, as a redundant version S7-417H is available. The fact that WinCC scripts are limited to 64K has never limited us in any project (im currently working on a pharmaceutical project with 4 S7-417 PLC's 2500 I/O and 90000 WinCC tags) because the use of scripts is only very seldom required. Besides the scripts in a drawing are only executed if the drawing is visible, this means that even if you have 1000 drawings, only the 10 (our installation has 10 clients) visible drawings would count (plus of course the global scripts) in this 64K limit.