Industry Online Support
Technical Forum
Navigation
Rating 
Thanks 13
8 Entries
| 5/12/2009 3:45 AM | |
|
Posts: 118 Rating:
|
I am creating more UDTs than using normal Data types in my project. Will it affect the CPU scan time? please give me more details on this. |
| 5/12/2009 7:59 AM | |
|
Posts: 2348 Rating:
|
UDTs exist only in your offline project, so they can't affect online scan cycle time. |
| 5/12/2009 2:45 PM | |
Joined: 10/7/2005 Last visit: 2/6/2025 Posts: 3033 Rating:
|
Dear Maha the answer is: It depends on how you use the UDT's! If you pass them on to a FC or FB and access their individual elements inside them, then YES it will make a difference in scan cycle time as the Step 7 compiler will create a fair amount of address register related code behind the scenes for you. Execution of this (hidden)code during runtime does of course add to the scan time. Please note: While you won't "see" the (hidden) extra code,Step 7 will correctly indicate the Fc or FB Block size in Simatic Manger, so please try this out yourself and be surpised (or scared) how fast you FC/FB grows in size with every UDT IN/OUT parameter accessthat you program into it. The same is by the way applicable for passing on STRUCT's or any other complex datatype to an FC or FB. Attached isdocument which offcially descibes the difference in memory requriements for direct versus UDT based access within an FC and FB (and which I interestingly enough can no longer locate on the Siemens web). Anyway, I hope this helps and good luck with your project. AttachmentMemory requirements for word load command.pdf (1025 Downloads) |
|
Cheers |
|
This contribution was helpful to
|
|
| 5/13/2009 4:00 AM | |
|
Joined: 10/7/2005 Last visit: 2/6/2025 Posts: 3033 Rating:
|
Hello again Maha in that case the answer is simply "NO, it will not create extra code nor affect scan time". Cheers Fritz |
|
Cheers |
|
| 5/13/2009 6:44 AM | |
|
Posts: 2348 Rating:
|
Very nice doc, thanks fritz.) |
This contribution was helpful to
|
|
| 7/4/2009 3:51 PM | |
|
Joined: 10/7/2005 Last visit: 2/6/2025 Posts: 3033 Rating:
|
Hallo Juergen I got it from the offical Siemens service and support web some years ago (it has an offcial Entry ID, the reasons I needed it was to convince someone "officially" that his 416 CPU's scan time of some 200ms is because of his excessive usage of UDT passing in and out of FC's/FB's). As said in my post, it does however seems to be no longer "online" (if I wouldn't know any better I'd say that Siemens does not want to make this publically known anymore). |
|
Cheers |
|
Follow us on