CPU usage Siemens softplc

Hey there professionals,

I've got a strange problem which i have already posted on another forum, but somehow is seems no-one knows how to explain it.

I am using a softPLC from Siemens (WinLC V4.1). Somehow the CPU of is suffering from peakloads. But these peakloads disappear when i ajust the settings for WinLC.



setting 1:
The setting in situation 1 is 15ms mimimum cycle time and 1 ms sleep time. So the total exucution time is 16ms. (The time needed to proces the program is approx 7ms). These were our default settings. (By setting the minimum cycle time we tried to reduce the overal CPU load, and this worked)

setting 2:
But when i ajusted the settings, sleep time 7ms and minimum cycle time 0ms, i saw a much more tranquil CPU load (see figure). But i can't explain it. The total exectuin time is now approx 14 ms, and that is even faster!!

I'm satisfied with this solution.
But i would like to be able to explain my solution, can someone?


Thanks Henk,
Philips, The Netherlands.

Hi Hanky.

I have no experience with WinLC.

But I have a few educated guesses.
I am guessing that when you set a minimum cycle time, then the WinAC proces actually stays active and uses the CPU time in the time after the program cycle has finished but the minimum cycle time has not yet finished. So this means that Windows cannot uses that time to service other processes.
With a sleep time in stead, Windows is probably free to service other processes after each program cycle.

Are you using WinAC with RTX extensions ?

I think that a CPU usage of 69% is a bit high for Windows anyway.
What kind of CPU does the PC have ?

JesperMP said:

Hi Hanky.

I have no experience with WinLC.

But I have a few educated guesses.
I am guessing that when you set a minimum cycle time, then the WinAC proces actually stays active and uses the CPU time in the time after the program cycle has finished but the minimum cycle time has not yet finished. So this means that Windows cannot uses that time to service other processes.
With a sleep time in stead, Windows is probably free to service other processes after each program cycle.

Are you using WinAC with RTX extensions ?

I think that a CPU usage of 69% is a bit high for Windows anyway.
What kind of CPU does the PC have ?

Click to expand...

That sounds logical, and could very well be the couse.
I'm not sure if we're using RTX extensions, what are they?
The PC has a P4 2GHz processor

Thx Henk

Hanky said:

I'm not sure if we're using RTX extensions, what are they?

Click to expand...

For example 6ES7671-0CC03-0YA0 should be "WinAC Basis" and 6ES7671-0RC05-0YA0 should be "WinAC RTX".

WinAC basis is "soft" real time ("only" a normal windows service), and WinAC RTX is "hard" real time (special low level realtime core running in parallel with windows).

Sales blah:

"SIMATIC WinAC RTX offers hard real-time and high performance. The optimized runtime system supports the processing of extensive and demanding PC applications in parallel with the control task. "
"SIMATIC WinAC RTX comprises the following components:

• Windows Logic Controller (WinLC RTX).
• SIMATIC NET OPC server.
• Real-time drivers for PROFIBUS-CPs
• Ardence RTX real-time core for guaranteeing real time and deterministics. "

• 
  

JesperMP said:

For example 6ES7671-0CC03-0YA0 should be "WinAC Basis" and 6ES7671-0RC05-0YA0 should be "WinAC RTX".

WinAC basis is "soft" real time ("only" a normal windows service), and WinAC RTX is "hard" real time (special low level realtime core running in parallel with windows).

Sales blah:

"SIMATIC WinAC RTX offers hard real-time and high performance. The optimized runtime system supports the processing of extensive and demanding PC applications in parallel with the control task. "
"SIMATIC WinAC RTX comprises the following components:

• Windows Logic Controller (WinLC RTX).
• SIMATIC NET OPC server.
• Real-time drivers for PROFIBUS-CPs
• Ardence RTX real-time core for guaranteeing real time and deterministics. "

• 
  

Click to expand...

Hello JesperMP

It does have

• SIMATIC NET OPC server.
• Real-time drivers for PROFIBUS-CPs

But i'm in doubt. In Windows there is an exacutable called S7wlcvmx.exe. This program runs the PLC software. Maybe this helpes?

Gr Henk.

What is the order number of the software ?

Also try to run the Windows Start ... SIMATIC ... Information ... Installed Software.