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PLC is stopped when trying monitor !

Created by: vananhtuan85 at: 4/19/2012 3:53 AM (10 Replies)

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4/19/2012 3:53 AM	Rate (0)
vananhtuan85 Posts: 4 Rating: (0)	Hello guys, I have PLC S7-300 CPU 314. It can run ok but when I connect to my PC by PC adpter .I monitor FC , PLChas stopped with error : Stop caused by time error( OB not loaded ... )Event ID: 16#4568 Ifcan not understand cause of PLC orPC ( ifPLC, why it can not run ok by itself. If not PLC why I try withother PC,it still stopped) Please help me !
vananhtuan85 Posts: 4 Rating: (0)
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4/19/2012 4:33 AM	Rate (5)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 9/15/2024 Posts: 3020 Rating: (1054)	Hello vananhtuan85 my guess (your info is a bit slim on detail) is that your CPU exceeded the cycle time which would lead to a a call of OB80 and a CPU stop incaseOB80 does not exist in yourCPU. The reason for the above asumption are thatonline monitoring requires extra resources in the CPU and as such extends the cycle time. Assuming your cycle time is already close the maximum allowed cycle time, going online will now "push it over the edge". I suggest you check the following: 1.) Open "Module information" (shortcut CTRL+D),go to the scan cycle tab andsee what the max recorded scan time was (NOTE: This may also crash your CPU again as this is also online monitoringand will icnrease the cycle time). In the bottom of this window you'll also see the configured max allowed scan cycle monitoring time. 2.) Assuming you are running borderline and need to or want tochange the scan cycle monitoring time, do so by opening HWconfig, double click on the CPU and changethe value for "Scan cycle monitoring time" in the "Cycle/Clock memory tab". I hope this helps and please let us know what you'll find
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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4/20/2012 8:03 AM	Rate (0)
soju Posts: 69 Rating: (2)	Just check if there is any endless loop executing in your program
soju Posts: 69 Rating: (2)
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4/20/2012 8:17 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Pls read carefully first post and you will see that problem arises ONLY when going online with CPU. So no endless loops here.
	Best regards, Darius
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4/20/2012 8:25 AM	Rate (0)
vananhtuan85 Posts: 4 Rating: (0)	Thank you so much, Mr.Fritz, You are right !I have already checked cycle time.It is problem. The PLC's cycle time is 20ms, when PLC stop, i see cycle time tap have red colour. I have change to 100ms( because I see other PLCs, it is adjust 150ms or 100ms) .After that , Plc is notstopped ( in the longtime). Icheck cycle time again, i see that : whenmonitoring , longest cycle is 21ms !!!! Could you please let me know, how many should I adjust this cycle time ? it make effect to PLC's perfomance ? Best wishes !
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4/20/2012 8:57 AM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 9/9/2024 Posts: 4515 Rating: (839)	Hello, Up to my knowlage, if you adjust cycle time to 100 ms, it will be fine specially the longest cycle is now 21 ms. Always try not to adjust cycle time value close to the longest cycle time value. As you know that cycle time varies from scan cycle to another. Factors that affect scan cycle time is many. May be your program it self and sometimes interrupts. It's to difficult to know exactly if the longest cycle (in your case here 21 ms) will be increase or not. Just come again after about 1 week and see it again. if it is arround this number, then adjusting scan cycle to 100 ms is more than enough. Hope this helps.
	Ayman Elotaify
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4/20/2012 9:37 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 9/10/2024 Posts: 10228 Rating: (1181)	Useful info - How to use SFC 64 w.r.t determine the Scan Cycle Time in Program?? S7-315F Safe. Expected cycle time. As Darius said: Also keep in mind that cycle time depends on complexity of algorithm more than on I/O count itself. It depends on how many PIDs you have, how much communication partners you configure and so on. I had a project with more than 5000 I/O and it was run on single S7-417H PLC and cycle time was 60-70 ms. So I can say 'it depends...'. If you know algorithm try to estimate cycle time from instruction list I gave you. Best regards, Hristo Mihalev

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4/26/2012 11:26 AM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 8/5/2022 Posts: 523 Rating: (32)	vananhtuan85 Thank you so much, Mr.Fritz, You are right !I have already checked cycle time.It is problem. The PLC's cycle time is 20ms, when PLC stop, i see cycle time tap have red colour. I have change to 100ms( because I see other PLCs, it is adjust 150ms or 100ms) .After that , Plc is notstopped ( in the longtime). Icheck cycle time again, i see that : whenmonitoring , longest cycle is 21ms !!!! Could you please let me know, how many should I adjust this cycle time ? it make effect to PLC's perfomance ? Best wishes ! this is because when you connect with PCto PLCCPU scan timeis increasedbecause it will take time to update variable valuefor Monitoring mode in S7 software.

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4/26/2012 12:08 PM	Rate (0)
IBN-Service Posts: 8946 Rating: (999)	vananhtuan85 ...Could you please let me know, how many should I adjust this cycle time ? it make effect to PLC's perfomance ? Best wishes ! First try to do: Hardware -> CPU -> Protection -> Prozess mode Then, online - mode will exceed your scan time only to the allowed value! But viewing of variable status may becomes a little slower.
IBN-Service Posts: 8946 Rating: (999)
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4/27/2012 9:30 AM	Rate (0)
gre_m Posts: 947 Rating: (45)	Hi,. may be should insert OB80 and increase speed between PLC and PG?
gre_m Posts: 947 Rating: (45)	Last edited by: gre_m at: 4/27/2012 9:31 AM
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