Coherent decoded process-data observation for one slave within one domain cycle.
A sample contains protocol truth only. It does not project machine state,
advertise semantic commands, or infer completion of application intent.
inputs contains only successfully decoded values. errors maps failed signal
names to decoder reasons for this cycle; no previous or substitute value is
retained for those signals.
Samples from different domains do not share a consistency boundary. Input
publication is change-driven; a sample is not emitted for every unchanged
domain cycle. Retained samples can outlive healthy cycling, so consult
EtherCAT.status/2 or EtherCAT.Diagnostics.domain_info/2 for current health
rather than treating the sample timestamp alone as a heartbeat.
observed_at is a host monotonic timestamp in microseconds, not wall-clock
time or EtherCAT distributed-clock time. Compare it only within the same VM.