Jump to content

State before POWER-OFF - is that possible?

Recommended Posts


Is it possible to set Unitronics V570 (in Visilogic 9.6.0) option which will set our outputs to the state that were before turning off our PLC? 

How is it possible?

As I know there aren't any bits in PLC (except SB) which saves their state even when PLC is power off.

Thank you for your time, cheers :)

Link to comment
Share on other sites

  • MVP 2023

Hi Rzas,

It looks like no-one has replied to this, so I'll have a quick go.

Yes it is possible, and there are myriad ways to go about it.  At the very simplest level, write a small program that turns a MB on and off from a key input.  Have that same MB directly running an Output, with both of them set to "None" in the Power up box.  Power off, and then with power on the MB retains it's status, and therefore the physical outputs remain the same as when the PLC lost power.  There are many more (sometimes complex) ways of doing what you want, but this shows you the basics. If your code will immediately alter these states on power up, you will need to put in delays, or programming that over-rides the code results initially.

I would be very careful retaining outputs on power up.....things like load shedding and correct interaction etc are very important.  I never do this AT ALL.  My devices all work from a sequenced startup, where the PLC initially stabilises it's readings and then powers everything up correctly.



  • Upvote 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...