Exchange formats: PLCopen XML, IEC 61131-10, AutomationML, DEXPI

First, identify the format by root element and namespace

Non-negotiables when you generate PLCopen XML

1. Required skeleton:

   • fileHeader with companyName, productName, productVersion and creationDateTime.
   • contentHeader with name and all three coordinateInfo/{fbd,ld,sfc}/scaling.
   • types/dataTypes and types/pous, which may be empty.
   • instances/configurations, which may be empty.

   Start from assets/plcopen-st-pou.xml.

2. ST and IL go in the XHTML namespace: either <ST><xhtml:p><![CDATA[…]]></xhtml:p></ST> as Beremiz writes it, or <ST><xhtml xmlns="http://www.w3.org/1999/xhtml">…</xhtml></ST> as CODESYS writes it. Read both. Write CDATA.

3. Graphical bodies:

   • localId is unique per body.
   • Every connection/@refLocalId points to an existing localId in the same body.
   • formalParameter names the producer's output pin. When it is omitted on a block, the first output that is not ENO is used.

   See assets/plcopen-ld-rung.xml.

4. Match the namespace to the importer. CODESYS-family tools export tc6_0200. The v2.0 → v2.01 changes are minor, but a strict importer can reject the other namespace.
5. Never trust XSD validation alone. A duplicate localId, a dangling refLocalId, an unknown derived type and broken ST all pass the XSD. Always run python3 ${CLAUDE_PLUGIN_ROOT}/scripts/plc_validate.py file.xml.
6. Task intervals come in two incompatible spellings. Beremiz writes T#100ms, while TwinCAT and CODESYS write ISO PT0.1S, and TwinCAT rejects t#10ms. Ask which tool will import the file.

CODESYS / TwinCAT / Machine Expert exports hide the project in addData

A CODESYS-family export can have an empty standard <pous/>, with every POU inside <addData><data name="http://www.3s-software.com/plcopenxml/pou">. The standard task interval can read PT0S while the real cycle sits in …/plcopenxml/tasksettings. Validator rules PX050 and PX051 flag both cases.

• When reading such a file, look inside those vendor blocks. Methods, properties, folders and object IDs live there too.
• When writing for a non-CODESYS consumer, put the POUs in the standard elements.
• Known loss: a GVL cannot hold both VAR_GLOBAL and VAR_GLOBAL CONSTANT through PLCopenXML, so the constants come back as plain globals.
• TwinCAT to TwinCAT: use the ZIP export, not PLCopenXML.

Both templates in assets/ validate against the official tc6_xml_v201.xsd, and they are re-checked by the plugin's test suite.

Schemas and licences

Neither XSD may be bundled with this plugin:

• The TC6 v2.01 document says "All rights reserved".
• The IEC 61131-10 schema is an IEC Code Component under the CCv1 licence.

Download them from https://www.plcopen.org/downloads/ ("XML Exchange": the TC6 v2.01 zip, and "Code Components of IEC 61131-10"). Then run plc_validate.py file.xml --xsd tc6_xml_v201.xsd, which uses xmllint or lxml.

References

• references/plcopen-xml.md: the full element model (interface sections, the graphical element table, SFC elements and qualifiers, instances, addData) and the IEC 61131-10 differences.
• references/automationml.md: IEC 62714 parts and editions, CAEX 2.15 vs 3.0, how logic is linked, AR APC, tools.
• references/dexpi.md: DEXPI versions, the Proteus structure, the instrumentation classes, ISO 15926 parts, and a method to derive an I/O list.

Converting logic between tools

Load the convert skill. In short:

• Graphical logic is portable only as PLCopen LD/FBD (with the CODESYS subset caveat), SIMATIC SD rungs or Rockwell neutral text.
• Never hand-write TwinCAT XmlArchive graphs or Control Expert .XBD/.XLD files.
• Siemens TIA has no PLCopen XML import for logic: it uses SimaticML or SIMATIC SD (see the siemens skill). This rests on a secondary source, so confirm it against the user's TIA version.