AC800M CPU Memory, Cyclic & Total load estimations for Sequential Function Charts
We look for sizing information regarding Sequential function charts (SFCs) in an System SV 6.0/6.1 environment.
- SFC Objects (eventually dependent on the number of actions and transitions?)
- Application example: Complex SFC based (batch) control modules
Asked 9 months ago
Answers
0
Since only one ( or sometimes 2 or 3 parallel ) step of the SFC is active at any one time, you can write a LOT of SFC code that doesn't really use much CPU time.
Take the largest step and apply the standard guidelines for calculating CPU load. Most SFC steps only perform simple calculations so the load will not be very high. Also allow 20 to 30 simple calculations for the step transition, which is monitoring timers, step completion etc. typically, this really isn't going to be very much at all.
Similarly for memory calculations, each line of code typically doesnt take much memory since its usually only a simple arithmetic calculation - but of course you need to count every line of code in the SFC. Again, assume about 20 to 30 simple operations for each transition.
When using the ABB Batch manager however, my experience has been that comms load is significantly higher. IMHO I would allow for a 40% comms overhead rather than the usual 30%.
Take the largest step and apply the standard guidelines for calculating CPU load. Most SFC steps only perform simple calculations so the load will not be very high. Also allow 20 to 30 simple calculations for the step transition, which is monitoring timers, step completion etc. typically, this really isn't going to be very much at all.
Similarly for memory calculations, each line of code typically doesnt take much memory since its usually only a simple arithmetic calculation - but of course you need to count every line of code in the SFC. Again, assume about 20 to 30 simple operations for each transition.
When using the ABB Batch manager however, my experience has been that comms load is significantly higher. IMHO I would allow for a 40% comms overhead rather than the usual 30%.
Answered 9 months ago
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