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SYNC and UNSYNC

Created by: safety4ever at: 2/10/2011 7:42 PM (5 Replies)

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2/10/2011 7:42 PM	Rate (0)
safety4ever Experienced Member Joined: 12/5/2006 Last visit: 5/27/2025 Posts: 73 Rating: (4)	In a configuration of S7 400 talking to few master drives over profibus I got something that confuses me a bit.The S7 program uses SFC 1514 to read andwrite to the drives, SFC11 is also used tosend a SYNC to thedrives bus, theprogram is made in such a way that B#16#20 is always sent to the mode input of SFC 11 i.e mode selected SYNC is continuously on. As I understood from the documentation that the outputs of the slaves are then frozen at the last processed value with a SYNC command until a new SYNC signal is regenerated.This means that the drives are supposed to runinsteady set point not accepting any changes until SYNC is recycling again from0 to 1 but thisnever happens, the SYNC enable signal is a static bit ina DB that was set to TRUE andnothing else writes to this bit,Is there something I am missing here?Those drivesare continuously changing set points through Profibus howdo they accept new values with this SYNC enable continuously on?

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2/10/2011 10:37 PM	Rate (0)
Hulzhex Gold Member Joined: 8/25/2005 Last visit: 5/30/2025 Posts: 1162 Rating: (111)	Hello safety4ever, every time you call the sfc11 with the command sync, this command will be send over the bus. Each successful call creats a new SYNC for your slaves. The slaves will stay in sync mode until they recive another command like the Unsync. One Unsync and the slaves are going to update their outputs immediately. Hope now it is a little bit more clear. Good luck Sabine

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2/11/2011 3:07 AM	Rate (0)
safety4ever Experienced Member Joined: 12/5/2006 Last visit: 5/27/2025 Posts: 73 Rating: (4)	Thanks Hulzhex (Sabine) So is it ok to have the field Mode continuously on B#16#20? I thought for changing the set points on the drives we had to go B#16#10 ( unsync) and back to B#16#20 (sync). In other words assuming the B#16#20 is on all the time would the call of the SFC 11 in the next cycle be enough to retrigger a new sync command without and "unsync" in between? Best regards

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2/11/2011 3:10 AM	Rate (0)
safety4ever Experienced Member Joined: 12/5/2006 Last visit: 5/27/2025 Posts: 73 Rating: (4)	Sorry forgot another thing also I noticed this bus also in the HW configuration is not marked under any group although Group one is selected in SFC 11 as a result error 7001 and 80b0 appear on the error field which makes me think this function is in the program without use.

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2/11/2011 11:21 AM	Rate (0)
Hulzhex Gold Member Joined: 8/25/2005 Last visit: 5/30/2025 Posts: 1162 Rating: (111)	safety4ever Sorry forgot another thing also I noticed this bus also in the HW configuration is not marked under any group although Group one is selected in SFC 11 as a result error 7001 and 80b0 appear on the error field which makes me think this function is in the program without use. ... so everything is clear now? Have you seen the information on manual: System Software for S7-300/400 System and Standard Functions Have a look at capture 16.2 You have to define a group within the hardwareconfiguration, select this group at the SFC 11 and then send you commands. Good luck Sabine

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2/11/2011 1:04 PM	Rate (0)
safety4ever Experienced Member Joined: 12/5/2006 Last visit: 5/27/2025 Posts: 73 Rating: (4)	Thanks Sabine.

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