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OB

Created by: Sindhu at: 6/22/2009 7:45 AM (8 Replies)

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6/22/2009 7:45 AM	Rate (0)
Sindhu Posts: 163 Rating: (0)	Im struck with programming in OB1 and OB35.whats the diff in writing the program in both OBs
Sindhu Posts: 163 Rating: (0)
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6/22/2009 8:10 AM	Rate (0)
yy1 Posts: 535 Rating: (112)	Dear Sindhu, I can see no difference in writing the program for these OBs. The OB1 is called cyclic, and the OB35 is called every 100 ms (you can change this time in HW-Config). But you can simply move the content of the OB1 to the OB35. Regards, yy1
yy1 Posts: 535 Rating: (112)
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6/22/2009 8:28 AM	Rate (0)
AMAZINGAHMED Posts: 719 Rating: (88)	OB1 runs every cycle, but OB35 runs every time interval. The OB35 time can be adjusted from the HW configuration. Usually OB35 (or similar cyclic OBs) are used in process automation, where the update time is not critical (such as temperature control). This helps to relief the scan cycle of some load.
AMAZINGAHMED Posts: 719 Rating: (88)
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6/22/2009 8:45 AM	Rate (0)
Sindhu Posts: 163 Rating: (0)	My project deals with Process control and process shutdown system.So why i have this doubt What im doing right now is process shutdown system: scaling of all analog values and the scaled values to be compared for HH or LL and the corresponding valve has to be shut off -This i have done in OB35.Then i find nothing to do with OB1 which is blank
Sindhu Posts: 163 Rating: (0)
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6/22/2009 8:49 AM	Rate (0)
Sindhu Posts: 163 Rating: (0)	How the cycle time can be adjusted in the hardware configuration
Sindhu Posts: 163 Rating: (0)
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6/22/2009 8:51 AM	Rate (0)
Sindhu Posts: 163 Rating: (0)	I found where to change the cycle time in the hardware config
Sindhu Posts: 163 Rating: (0)
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6/22/2009 8:54 AM	Rate (0)
yy1 Posts: 535 Rating: (112)	Dear Sindhu, you can change the time in the 'Cyclic Interupts'-tab of the CPU-properties. Regards, yy1
yy1 Posts: 535 Rating: (112)
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6/22/2009 9:11 AM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 12/21/2025 Posts: 929 Rating: (309)	Hello Sindhu, The point is that OB35 is a cyclic INTERRUPT which means it has higher priority than OB1which couldbe interrupted by any other OB. Yes OB35 is used in process control for example to fix the time between each call of PID block to havecorrect integral and derivative action. OB3Xs arealso used to contain safety programs in S7-400F/FH which is definitely not your case. If your code is not divided between OB1& OB30 and there's nothing important require cyclic interrupt like PID blocks, why don't youput your code inthe free cycle OB1 for faster processing instead of waiting for cyclic interrupts. Best regards. H-H

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6/22/2009 3:06 PM	Rate (0)
Ayman Elotaify Diamond Expert Joined: 5/28/2008 Last visit: 1/12/2026 Posts: 4522 Rating: (843)	Dear Sindhu and yy1, I think the following thread will be helpful for you both. what happen when OB1 scanning and Cyclic Interrupt OB come ? Regards,
	Ayman Elotaify
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