PN station failure — PROFINET IO device failure

The IO controller lost its application relation with an IO device. The device stopped responding within its watchdog window, so the controller declared it failed and its inputs go to substitute values.

Start free PROFINET / S7 → canonical

Diagnosis

When you hit this

Cable or connector fault, particularly on a moving machine where the cable flexes.
Update time and watchdog factor set too aggressively for the network's actual load.
A device rebooting, whether from a power dip or a firmware update.
Duplicate device names or IP addresses on the segment.

Resolution

How to fix it

Read the diagnostic buffer
The CPU's diagnostic buffer timestamps the failure and names the device. It is far more specific than the aggregate alarm.
Relax the watchdog
Watchdog equals update time times reduction ratio. If failures are intermittent and load-correlated, the window is too tight.
Check for duplicate names
PROFINET identifies devices by name. Two devices with one name produce failures that move around the network.
Inspect the physical layer
Port statistics on the switch will show CRC errors long before the link fails outright.

Normalization

What Forge does about it

This is a transport failure, so there is nothing for Forge to normalize: the reading never arrives. What Forge does is refuse to let the gap look like good data. The read-time dropout check flags a field that fell to zero and recovered as a communication glitch rather than a real measurement, and the stuck-sensor check fires when a value repeats for 20 consecutive readings — which is what a cached or last-known value looks like after a link drops. Forge does not retry or reconnect for you; that is your client's or your gateway's job.

Connect

Normalize PROFINET / S7 telemetry

One MCP endpoint serves every protocol adapter. 16,908 curated mappings, 366 canonical fields.

# normalize telemetry from PROFINET / S7 — and 13 other protocols

claude mcp add --transport http forge https://mcp.foundrynet.io/mcp \

--header 'Authorization: Bearer YOUR_FORGE_KEY'

✓ forge connected — 32 tools available