Applicable Systems
GP4000 Series
Symptoms
Ethernet/IP implicit I/O connection times out repeatedly with error code 0x0204.
Possible Causes
- RPI (Requested Packet Interval) set too aggressively for the network load.
- EtherNet/IP scanner class conflict due to another master owning the connection.
- Network switch QoS not prioritizing Class 1 implicit traffic over best-effort data.
Troubleshooting Steps
- Step 1: Increase the RPI from 10 ms to 50 ms in the GP-Pro EX Ethernet/IP driver settings.
Connection stabilizes and no timeout errors occur for 1 hour. - Step 2: Use RSWho or similar scanner to verify no other PLC or HMI owns the connection.
Only one ownership entry is present for the target adapter. - Step 3: Enable IGMP snooping and DSCP prioritization (EF/AF) on the managed switch.
Packet capture shows Class 1 traffic is forwarded with highest priority and <1% loss.
How to Reset
Adjust RPI to a conservative value, resolve ownership conflicts, and enable industrial Ethernet QoS.
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Source: Pro-face SP5000 Series EtherNet/IP Application Note
Category: HMI
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