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Issue related to OB86 call after CPU startup in case of DP Slave failure

Created by: hdhosseini at: 6/29/2013 5:57 PM (5 Replies)

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6/29/2013 5:57 PM	Rate (2)
hdhosseini Diamond Member Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	Hello friends, We had a discussion in "Expert- Conference" related to calling OB86 after CPU startup in case of DP Slave failure by operating system of CPU.My experienced expert friend in filed of "Decentral Peripherie" fritz provided some points while discussion that I summarize them here.We confirm that it is possible that operating system of CPU doesn't call OB86 right after startup even if you have lost a slave when CPU was stopped or in power off mode.As a remedy we propose the following solutions.We will ask the moderating team to provide an FAQ out of this tip, but till official release you can rely on this tip: You can perform all needed diagnostics(for H-system,DP slaves and channels) in one of the "restart OBs". You generally can do your DP Slave status evaluation with SFC51in the cyclicuser program (instead of OB82 and/or 86) to avoid exactly the potential problem that faulty DP Slaves go unreported.To ensure you don't miss any shortlived DP Slave failures, you do though latch a bit in OB82 and another one in OB86 on a coming event. These bits are then combined together with a 2 sec pulse bit where SFC51 is called in the cyclic program.This way you get immediate call of SFC51 if and when OB82 or 86 are triggered as well as regularily checking every 2 seconds to cover DP slave faults while CPU wasoff and to update the status when the DP Slaves come good again. We also discussed the possible extra execution load by using the 2nd method that by checking THIS manual , exposed load considered tolerable even for the slowest S7-300 CPUs. Many regards Hamid Hosseini
	Last edited by: hdhosseini at: 8/4/2018 3:52:24 PM Demo Channel on Youtube
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4/8/2015 1:20 PM	Rate (0)
aleb2 Experienced Member Joined: 7/12/2006 Last visit: 11/7/2024 Posts: 130 Rating: (0)	You mean to set a bit in OB82 and another in OB86 (on incoming event) then in OB1 RESET them after called SFC51?

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4/8/2015 2:28 PM	Rate (0)
hdhosseini Diamond Member Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	aleb2 You mean to set a bit in OB82 and another in OB86 (on incoming event) then in OB1 RESET them after called SFC51? Hello, Thanks for the interest in this topic, SET same memory in OB82/86 in case of incoming event.In one of cyclic interrupts(fast), OR the coming error signal with another alternating signal and feed it to REQ signal. The alternative would be using OB100 and calling SFC51 there. I hope these comments help, Hamid Hosseini
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4/11/2015 10:21 PM	Rate (0)
aleb2 Experienced Member Joined: 7/12/2006 Last visit: 11/7/2024 Posts: 130 Rating: (0)	Something like that?: OB86: SET M0.0 OB82: SET M0.0 OB1: CALL SFC51 with REQ=M0.0 R M0.0

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4/13/2015 7:02 AM	Rate (0)
hdhosseini Diamond Member Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	This is what I am thinking about OB86: SET = M0.0 OB82: SET = M0.0 OB3X: AN M0.1 =M0.1 O M0.0 O M0.1 = M0.2 // or a temp memory CALL SFC51 with REQ=M0.2 CLR = M0.0
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This contribution was helpful to 1 thankful Users dozsa.a

8/19/2015 9:45 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by AutoGen_1045685 is split to a separate thread with the subject PLC losses communication with one of the dp slaves. Best regards Min_Moderator

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