3/8/2024 5:11 PM | |
Joined: 7/10/2023 Last visit: 8/6/2024 Posts: 3 Rating: (0) |
I am currently working with Sequential Function Charts (SFCs) using the PCS 7 SIMATIC Manager environment, and I have encountered a point of confusion regarding the operational differences between the "Abort" and "Stop" commands within an SFC. Specifically, I'm looking to understand the precise behaviors of these two commands, especially in terms of how they impact the terminating sequence of a step that is currently being executed. From my understanding, the "Abort" command is used to immediately halt the execution of a sequencer, while the "Stop" command seems to allow for a more orderly termination of processes, ensuring that all necessary sequences are executed before the sequencer fully stops. However, I am particularly interested in detailed clarification on the following points:
I have gone through the documentation available to me (see attached), but I would greatly value insights or explanations from the community here, especially from those who have encountered and resolved similar questions in their projects. Thank you in advance for your time and assistance. I look forward to any clarification or additional resources you might be able to provide. Attachments7sfcs7b_e.pdf (399 Downloads) |
Last edited by: RKStmuller at: 03/08/2024 17:23:05Last edited by: RKStmuller at: 03/08/2024 17:24:29 |
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3/9/2024 7:20 PM | |
Joined: 3/14/2008 Last visit: 10/15/2024 Posts: 2111 Rating: (942)
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Hi, If you take a look at paragraph 3.3.2 in your attachment you can see the operating state logic of SFC. The SFC is based according ISA88 standard and as you said Abort is used to stop the process immediately and Stop is used for a controlled way of stopping the proces. When Abort is used, the sequence goes to Aborting and then to Abort. In the SFC you can program the sequencers if you like. So when Aborting is called, you can execute steps in the Aborting sequencer. Same applies for Stopping and Stopped. When in Stopping, the SFC can go to Aborting as well. When Aborted/Stopped is active, you can use Reset command to go back to Idle and then the SFC can be started again. From Aborted you can go to Starting when the Start command is used. If you want to use logic in Aborting state for example, the make sure the startcondition for that sequence is set as follows: SFC :=Aborting. If the SFC is in Aborting, the sequencer is called and the steps are executed. If the Aborting sequencer is not used, the SFC will still call Aborting, but no step logic is executed. When the SFC is in Starting, Run, Holding etc. and for example Aborting is called, then the SFC will immediately exit the current sequencer (SFC goes to END step of that sequencer) and starts the Aborting sequencer. What I always use do is using Aborting to set all CM to rest and Completing is used to stop the process in a normal way. Completing is also a sequencer that can be used. I do not use Stopping since I'm used to Batch and batch will normally use Completing to stop the process. |
Last edited by: Oreca at: 03/09/2024 19:31:54If I could help you, you can use the RATE button. Thank you. |
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3/13/2024 5:35 AM | |
Joined: 3/14/2008 Last visit: 10/15/2024 Posts: 2111 Rating: (942)
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Hi, When step is activated, the Initialization phase is executed, one the step is active, the Processing phase is activated while the step is being executed. When the transition is fulfilled, the Termination phase is executed. When the step is in Processing and you press Abort (or Stop or Complete), then the Termination phase of that step is excecuted and the current sequencer goes to END and initiates the Aborting sequencer. Hold is different, because when Hold is activated, the current step which is in Processing goes to Holding sequencer without executing the Termination phase of the step. Please bear mark, if you have a step with logic in the Intitialization phase and in that step Hold is activated, then after Resume is pressed and the SFC goes back to the step where it entered Hold, then the Intialization phase is not executed anymore.
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If I could help you, you can use the RATE button. Thank you. |
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