0x01 (0x01) — Connection failure

A connection-related service failed. General status 0x01 is nearly meaningless on its own — the extended status word carries the real cause.

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Diagnosis

When you hit this

Extended 0x0100: connection already in use. Another client owns the connection point.
Extended 0x0113: out of connections. The adapter's connection pool is exhausted.
Extended 0x0114 or 0x0115: vendor id or product type mismatch, meaning the electronic key does not match the device actually present.
Extended 0x0116: revision mismatch, common after a firmware upgrade.

Resolution

How to fix it

Read the extended status
Do not debug 0x01 alone. Every serious CIP stack exposes the extended word; log it.
Relax the electronic key
If the mismatch is a deliberate firmware upgrade, set the key to compatible-module rather than exact-match.
Count connections
Small adapters support very few CIP connections. Every scanner, HMI, and test tool consumes one.

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.