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LESSON

Tag Group Overview

Description

Tag Groups determine the execution rate for one or more tags in a Tag Provider.

Video recorded using: Ignition 8.1

Transcript

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[00:00] All tags in ignition have some concept of execution. A status code from the PLC is only valuable if they get new values occasionally. To implement and organize the idea of tag execution, ignition has tag groups. A tag group is a collection of tags that share the same execution logic. So let's create a new tag group. To do that we'll open up the tag group editor and note that each tag group is for a particular tag provider, and you can see that it says for provider default here. Each provider starts with a couple of tag groups and default and default historical. And if you select default, you can see that this one is using a mode of direct in a rate of 1000 milliseconds. We'll talk about the mode in just a moment. Now I'm going to add a new tag group by clicking on the plus icon here. Then I'll give my new group a name. And I can select the mode. I'll use direct but we'll cover driven and leased modes in future videos. Now a direct mode allows our tags to run at a specific rate all the time. So for example, I can type in 5,000 milliseconds and that means, every time we'll get a new value, every five seconds. Now, the primary reason for a tag group is to control the mode and rate of execution, but there are other properties here. The data mode will allow us to choose a subscribed or polled mode. Subscribed means we're going to ask the OPC server to get a tag value at a particular rate. Whereas polled means, every five seconds, we would ask for a new value. The subscribed mode is more efficient but the polled mode gives us more precise control over how we ask for our tag values. I'll go ahead and select polled here for our data mode. The read after write setting, if we change that to true, it will force a read for this tag after every time you write to it. And this is really useful when you have a very slow tag group. So that way you'll pull in the new tag information very quickly, instead of waiting until the next execution. The optimistic writes setting will allow us to immediately assume that the value wrote correctly and the write time out there will say that if it doesn't confirm that it's written correctly by this timeout, then it'll revert the value. Now I'm not going to talk about all the different properties here and specifically we'll cover a history properties when we talk about tag history. These are specific to when this group is being used for storing tag history. So I just set a name and I have a direct mode with a rate of 5,000 milliseconds. I'll go ahead and click okay. And that will create our new tag group. To use that new tag group, I do have to go and select to one or more of my tags. I can double click it to edit that particular tag. And then you can see it's running at a one second rate because our tag group is using the default. I can change this tag group to use my new tag group, my tag group, and then hit apply. And then you can see if we watch our executions here, now it'll be running at a five second rate, instead of a one second rate. We'll talk more about the other two types of tag groups in future videos.

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