siemens/tia-portal-ai-extensions/plc-data-types

PLC Data Types (UDTs)

Overview

PLC Data Types (UDTs) live in PlcSoftware.TypeGroup as PlcType objects. They are completely separate from blocks (PlcSoftware.BlockGroup) and from library types (GlobalLibrary.TypeFolder). This skill covers TypeGroup navigation, recursive search, and the XML export structure for UDTs.

Required Namespaces

using Siemens.Engineering.SW;
using Siemens.Engineering.SW.Types;

Required Assemblies

• Siemens.Engineering.Base.dll
• Siemens.Engineering.Step7.dll

1. TypeGroup Structure

PlcSoftware
└── TypeGroup                     ← PlcTypeSystemGroup (root for all UDTs)
	├── Types                     ← PlcTypeComposition
	└── Groups                    ← PlcTypeUserGroupComposition
		└── PlcTypeUserGroup
			├── Types
			└── Groups            ← can nest arbitrarily deep

PlcTypeUserGroup sub-folders are purely organizational — they are NOT SW-Units.

2. Finding a UDT

Types.Find(name) searches only the current group level. For deep search, recurse into Groups:

PlcType FindTypeRecursive(PlcTypeGroup group, string name)
{
	var result = group.Types.Find(name);
	if (result != null) return result;
	foreach (var sub in group.Groups)
	{
		result = FindTypeRecursive(sub, name);
		if (result != null) return result;
	}
	return null;
}

To search across the entire PLC (root and all SW-Units), see `sw-units`.

3. Creating and Navigating Sub-Groups

var group = plcSoftware.TypeGroup.Groups.Find("FolderA")
		 ?? plcSoftware.TypeGroup.Groups.Create("FolderA");

Group nesting is unlimited. Always use Find before Create to avoid duplicates.

4. UDT XML Export — Section Name Rule

When a PLC Data Type (SW.Types.PlcStruct) is exported via Openness, its members are always inside <Section Name="None">.

<SW.Types.PlcStruct>
  <AttributeList>
	<Interface>
	  <Sections xmlns="http://www.siemens.com/automation/Openness/SW/Interface/v5">
		<Section Name="None">          <!-- ALWAYS "None" for UDTs — never "Static" -->
		  <Member Name="SetPoint"      Datatype="Real" />
		  <Member Name="Enable"        Datatype="Bool" />
		  <Member Name="Config"        Datatype="&quot;MyNamespace.ConfigUDT&quot;" />
		  <Member Name="Buffer"        Datatype="Array[0..9] of Real" />
		</Section>
	  </Sections>
	</Interface>
	<Name>MyUDT</Name>
  </AttributeList>
</SW.Types.PlcStruct>

Critical rule: Never look for <Section Name="Static"> when parsing UDT exports — that section name belongs exclusively to Global DBs (SW.Blocks.GlobalDB). UDTs always use "None".

5. Member Attribute Formats

Each <Member> element carries:

When parsing member data types programmatically, unescape " → " before processing.

Quick Reference

Common Failure Modes

Related Files

• `sw-units` — PLC-wide UDT search across root and all SW-Unit TypeGroups
• `global-library` — placing UDTs from library (MasterCopy or LibraryType path)
• `blocks` — blocks live in BlockGroup, not TypeGroup