Online edits do not have to stop the PLC.
"Like any system if you change a function block (parameters)you then have to find all instances of the block, change them."
This is what I mean by the AB and Siemens camps being so different they can't relate. There is no FB in AB............no the SLC500 anyway.
With a SLC500, I can go online............really online and there is only ONE method of going online. And since the offline file matches the online file I know what I am seeing in AB is what is actually in the PLC and running right now. Or I can look at whats in the PLC and use just the comments from the my offline file that does not match exactly, like if someone edited the original while I wasn't looking. Then only the edited parts would be missing comments.
Now that I am online, I can change a rung or 2 or 3 or 4 .I never did more than 3 or 4 at a time not sure what the limit is. Probably limited by the PLC memory because it holds the edited and unedited versions in memory until you accept it as permenant.
So I edit away and then chose test edits..............where I can see it work live real time but with the ability to quickly hit "undo" or untest and put it back the way it was. I can go back and forth if I like.
Then when I like it , I can chose accept edits and compile and it is permanent and in the PLC ................without ever going into stop mode.
Now if you want to do offline edits and load them all at once , then you need to "download" and this causes a stop of the CPU.
The big difference is that online editing is slower , the communications and screen updates slow down everything. So most people use online for small changes when you can't stop the process and offline for large changes when you have time to stop production and do testing.
I have heard that the new AB does have FBs in which case it would have to be as you say. BUt not so with the SLC500.
With Siemens, I have not found a way to edit a block and download it and then undo it while testing a new edit. And I have to remember to download the DB that goes with the FB even though they are linked and to me should considered one item for downloading especially if the parameters have been changed. But that's just me.
I have only had to stop the PLC in Siemens when I download the system data. Otherwise the PLC stays in run mode and downloads the new block and keeps running.
I would not do this in a production machine unless I was confidant it would cause problems with the process. I never had a problem using the online edit in AB. But I haven't used Siemens while in production yet so I don't know what effect changing blocks will have on the process.
Not that either is a better system.........that's not my angle here.........just makeing a clarification so it is easier to understand the differences.
"Like any system if you change a function block (parameters)you then have to find all instances of the block, change them."
This is what I mean by the AB and Siemens camps being so different they can't relate. There is no FB in AB............no the SLC500 anyway.
With a SLC500, I can go online............really online and there is only ONE method of going online. And since the offline file matches the online file I know what I am seeing in AB is what is actually in the PLC and running right now. Or I can look at whats in the PLC and use just the comments from the my offline file that does not match exactly, like if someone edited the original while I wasn't looking. Then only the edited parts would be missing comments.
Now that I am online, I can change a rung or 2 or 3 or 4 .I never did more than 3 or 4 at a time not sure what the limit is. Probably limited by the PLC memory because it holds the edited and unedited versions in memory until you accept it as permenant.
So I edit away and then chose test edits..............where I can see it work live real time but with the ability to quickly hit "undo" or untest and put it back the way it was. I can go back and forth if I like.
Then when I like it , I can chose accept edits and compile and it is permanent and in the PLC ................without ever going into stop mode.
Now if you want to do offline edits and load them all at once , then you need to "download" and this causes a stop of the CPU.
The big difference is that online editing is slower , the communications and screen updates slow down everything. So most people use online for small changes when you can't stop the process and offline for large changes when you have time to stop production and do testing.
I have heard that the new AB does have FBs in which case it would have to be as you say. BUt not so with the SLC500.
With Siemens, I have not found a way to edit a block and download it and then undo it while testing a new edit. And I have to remember to download the DB that goes with the FB even though they are linked and to me should considered one item for downloading especially if the parameters have been changed. But that's just me.
I have only had to stop the PLC in Siemens when I download the system data. Otherwise the PLC stays in run mode and downloads the new block and keeps running.
I would not do this in a production machine unless I was confidant it would cause problems with the process. I never had a problem using the online edit in AB. But I haven't used Siemens while in production yet so I don't know what effect changing blocks will have on the process.
Not that either is a better system.........that's not my angle here.........just makeing a clarification so it is easier to understand the differences.
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