Externally writing to an AOI's local tag

[phuz]

I came across something and it's baffling me as to how it is working.
The AOI is for a valve and it has parameters for auto_status, hand_status, and off_status. It has local tags for GoToAuto, GoToHand, and GoToOff. Because they are local, they are not visible in the tag tree, and therefore cannot be referenced in logic. However, the IFIX application writes to these GoTo tags and it works just fine.
How is this working?

 

[jkerekes]

FactoryTalk View SE/ME: Logix platform Local tag Access Guidelines

68753 | Date Created: 05/21/2010 | Last Updated: 05/23/2016
Access Level: TechConnect

 

[phuz]

Wow, that explains it. So an HMI can reference it, but the open logic cannot.
Thanks for the quick answer.

 

[Yokes9]

Hi Phuz,

If you go to the AOI in the Controller Organizer tree view on the left of the screen and click "Parameters and local Tags" then find the tag that you want to be able to read/write to. There is an option for external access change to Read/Write. This is very useful if you want to have a UDT inside an AOI that you can access through out the program or HMI. The only bad part is it is hard for people to understand what you are doing and therefor best to avoid.
This only works on version 20 and above.

 

[phuz]

Hi Phuz,

If you go to the AOI in the Controller Organizer tree view on the left of the screen and click "Parameters and local Tags" then find the tag that you want to be able to read/write to. There is an option for external access change to Read/Write. This is very useful if you want to have a UDT inside an AOI that you can access through out the program or HMI. The only bad part is it is hard for people to understand what you are doing and therefor best to avoid.
This only works on version 20 and above.

No, that only exists for parameters, not local tags.
Thanks though. The previous answer was just what I needed!

 

[Yokes9]

No, that only exists for parameters, not local tags.
Thanks though. The previous answer was just what I needed!

You are correct after looking at it I did say the wrong location to change the access. You would right click the AOI in the TreeView and go to properties/ Local Tag tab you might have to right click the column headers and select toggle column External Access then you can change external Access to None, Read or Read/write. or you can Right click the tag and at the bottom is the "Set External Access For xxx".

This is very handy for using internal UDTs with AOIs or AOIs inside of AOIs and displaying the information on the HMI.

My mistake . Just wanted to clear up how to do it for people that don't have Tech connect account. Don't want to send people on a wild goose chase.

 

[phuz]

LOL.
Thanks for the insight.