libplctag
How to read External Access of Tags and Usage of UDTs?
Hello,
is it possible to read the External Access (Read/Write, Read Only, or None) of Variables and Usage of UDTs? (Input, Output, InOut, Local) of UDTs?
Tags in Logix Designer:
UDTs in Logix Designer:
Thanks!
This is not exposed in libplctag.
Quickly browsing the Rockwell documentation there was some info on this:
- pg12 of the Logic 5000 Controllers Data Access manual
- page 60 of the Logix 5000 Controllers I/O and Tag Data manual
Hi.
I looked at pages 39 and 48 of the documentation
If I understand correctly, the information I wanted to access is not available via the Get_Instance_Attribute_List (0x55) and Get_Attribute_List (0x03) services.
Thank you anyway!
Maybe it is accessible via Get_Instance_Attribute_List (0x55) and Attribute 10:
Source: https://docs.pycomm3.dev/en/latest/_modules/pycomm3/logix_driver.html#LogixDriver.get_tag_list (scroll down to function get_instance_attribute_list_service)
Thanks for the tip. This looks interesting. I wonder if just always requesting attribute 10 will work? Each attribute has a separate status response, so it might work as long as we can see that asking for attribute 10 fails on some systems and the others succeed.
I wonder why the pycomm3 author is pulling attribute 6? I found attribute 8 by experimentation.
It would be really nice to be able to read tags that are based on UDTs. I am curious, what is the currently the best practice on that?
