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Prevent process image from being cleared during restart

Created by: RandomCoder at: 3/4/2011 12:47 PM (4 Replies)

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3/4/2011 12:47 PM	Rate (0)
RandomCoder Experienced Member Joined: 8/16/2010 Last visit: 1/19/2022 Posts: 50 Rating: (8)	Having wasted the last hour looking fora solution it is timethat Iask for your help. The step 7 help states that... "When an S7-400 CPU is restarted, the remaining cycle is executed, and as default, the process image output table is cleared. You can prevent the process image being cleared if you want the user program to continue with the old values following a restart" But how do I accomplish this? My process requires that the outputs remain in the same state as when the PLC lost power. Please can someone provide a step by step guide as to how this can be set? I am using Step7 V5.2 with a 414-2DP PLC. Many thanks, RandomCoder

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3/4/2011 1:31 PM	Rate (0)
plcordoba Regular Member Joined: 1/8/2007 Last visit: 10/5/2022 Posts: 21 Rating: (1)	Hi!! you can use remanent data or DB areas (if you have battery inside PS) to freeze anything of plc after power fail To config this, open HWconfig and looking in cpu options Best Regards!!!

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3/4/2011 2:26 PM	Rate (0)
RandomCoder Experienced Member Joined: 8/16/2010 Last visit: 1/19/2022 Posts: 50 Rating: (8)	plcordoba, Thankyou for your reply but I have already poked around in the PLC "Object Properties" and I'm at a loss as to what I need to set. In the "Retentive Memory" tab it asks for number of bytes starting with MB0, Timers starting T0 and Counters starting C0. No mention of outputs??? The area's box is greyed out but this looks as though it only relates to DB areas. Am I doing something wrong or is it not possible with my PLC? I have a work around using a one shot on powerup, but as the help states that it is possible to retain the process image I would rather do this if I could only find the way to do it. Kind regards, RandomCoder

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3/4/2011 2:45 PM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 5/30/2023 Posts: 2966 Rating: (1025)	Hello RandomCoder you need to set the restart mode to "Hot Restart" (which means OB101 is used) in the "Startup" tab of the CPU properties if you want to retain the process image (you can additonally select to "reset the outputs at Hot restart" or deselect this option too). Note thatthe program will in this mdoe resume at the point in the program where if stopped when the power failed. Please make sure to use the "Help" button on the "Startup" tab of the CPU propertiesand read up on the rarifications of this mode. I hope this helps
	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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3/4/2011 3:05 PM	Rate (0)
RandomCoder Experienced Member Joined: 8/16/2010 Last visit: 1/19/2022 Posts: 50 Rating: (8)	Hello fritz, Thank you for your help. I have already read the help files relating to OB100, OB101 and OB102 and this is where I intended to place a startup one-shotflagif unable to discover how to retain the output image, which would have then loaded with some default values. Theapplication I'm working on does not present any hazards to the machine or any personsif the outputs were to come on unexpectedly and I am fully aware of the ramifications of what I have requested. What I had not realised is thatit is referred to as a "Hot restart" and all that is required is tosimply check the option within the CPU startup tab which then enables the other "Reset outputs at hot restart" check box that I had been frustratingly unable to unlock. Simple when you know how! Thanks, RandomCoder

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