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Question regarding Control Modules SCANNING done by controller (Our Example SX Controller)

Hey Guys,
 
I have a question related to Execution Phasing of Control Modules.
Phasing is basically numbering the control modules (Count of Control modules) that can be executed at the same time.
If Controller Base Time is 50 ms and the controller having 500 Control Modules, then, how the controller is going to scan these 500 Control Modules. Whether these 500 Control Module will start executing at the same time or it will done in batches?.
In Emerson System how the Batching of Control Modules that needs to be executed at the same time is done?? Whether the configurator has provision to decide how to batch these control modules to execute at the same time.
 
What is the Execution time Parameter of control Module means?? My understanding for execution time means that particular module will be “Read Input, do required calculations and send Output” after that specified time interval. Although the controller base time is 50 ms, but as the control module execution time has been defined as 1sec, then after every 1sec only the controller will execute/update the blocks containing In that particular control module.
 
Also, what can we understand by the “Controller FREE TIME” and “slippage” in the controller?
 
For example if a controller base time is 50 ms, Number of control modules 500,  and control module has an execution time of 1 sec then:
 
Time(s)=n à Execute Control Module (Read AI, Calculate PID, Send AO as per execution order of the CM), but along with executing this control module , the controller also executes other control modules within 50 ms. For executing one control module the controller may take fraction of the base time i.e. 50 ms….
T(s)=n + 1Sec à Again Execute the same Control Module (Read AI, Calculate PID, Send AO as per execution order of the CM)                                                    
T(s)= n + 2Sec à Again Execute the same Control Module (Read AI, Calculate PID, Send AO as per execution order of the CM) T(s)=1+x+1 à Repeat the cycle again and so on.
 
 
Thanks for any responses.
 
Bhargav.Chitti

1 Reply

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