What this EtherCAT ESI inspector checks
The bounded XML parser inventories vendor and device identity, groups, ordered SyncManagers, RxPDOs, TxPDOs, and their entry indexes, subindexes, names, data types, and bit lengths. It resolves device-to-group and PDO-to-SyncManager relationships, detects duplicate PDO identities, validates default-size ranges, finds overlapping SyncManager memory spans, and checks whether assigned PDO bytes fit their declared SyncManager.
How process-image offsets are calculated
Each entry starts after the preceding entries in its PDO. PDOs assigned to the same SyncManager are then concatenated in document order, producing an SM-relative bit offset and byte:bit address. RxPDO means data received by the SubDevice—outputs from the MainDevice. TxPDO means data transmitted by the SubDevice—inputs to the MainDevice. Unassigned PDOs remain visible but are not presented as active hardware mapping.
What the optional SII comparison proves
The SII parser reads the fixed 128-byte area and bounded category chain, including Strings, SyncManager, TxPDO, and RxPDO records. Comparison can expose a mismatched identity, address, size, control byte, enable field, SM assignment, entry order, object coordinate, or bit length. It cannot establish which image is installed on a live device unless the bytes were read from that exact device by trusted engineering software.
Safety and conformance boundary
This is a read-only preflight, not an EtherCAT conformance or commissioning tool. It implements a bounded subset useful for identity and static process-data review; it does not validate the complete ETG.2000 schema, SCI/modular profiles, FMMU programming, mailbox behavior, CoE object dictionaries, distributed-clock timing, EtherCAT P, vendor extensions, EEPROM configuration CRC, firmware agreement, or live network behavior. It never opens an adapter or writes an EEPROM. Confirm findings with the vendor ESI, the applicable ETG specifications, a supported configurator, and controlled machine testing.
Frequently asked questions
Why is an SII file optional?
The ESI is the detailed offline XML description. The SII is the smaller device-readable representation. ESI-only inspection still audits static XML relationships and layout; adding SII enables evidence-based comparison.
Why are offsets grouped by SyncManager?
PDO assignment determines which SyncManager carries a process-data sequence. Grouping prevents an unassigned or differently assigned PDO from silently shifting an unrelated map.
Does a matching report mean the device is safe to run?
No. Matching files do not prove live hardware identity, configuration, timing, electrical safety, machine logic, or conformance. Treat the report as review evidence only.
Authoritative references
The EtherCAT Technology Group explains the distinct roles of ESI XML and the non-volatile SII, publishes the ETG.2000/ETG.2010 specification catalog, and provides the public SubDevice Implementation Guide. The open-source IgH EtherCAT Master provides independently inspectable implementations for SII Strings, General, SyncManager, and PDO category decoding.
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