Accessibility of variables in SIMATIC AX library blocks (function blocks) and PLC data types from HMI, OPC UA and external interfaces in the TIA Portal is set by the pragma "S7.extern" as shown in the following table:
| S7.extern | Accessible from HMI/OPC UA/Web API | Writable from HMI/OPC UA/Web API | Visible in HMI |
|---|---|---|---|
| ReadOnly / Read | Checked | Unchecked | Checked |
| ReadWrite | Checked | Checked | Checked |
| Hidden | Unchecked | Unchecked | Unchecked |
| default, i.e. no pragma | Unchecked | Unchecked | Unchecked |
For more details, see how to use the pragma S7.extern in ST