Networks & drives

ProSoft PLX32 EIP-to-Modbus TCP drops on a Yokogawa Centum with A3B0

Nora Voss · DCS specialist

PLX32-EIP-MBTCP in front of Centum VP. Every few hours Modbus TCP dies, DCS shows A3B0, then it comes back. Ethernet/IP side to the Logix stays up. Looking for a scan-class or timeout that actually stopped the flapping without padding the whole map.

Malik Jennings · OT
A3B0 on that pairing was a Modbus unit-id mismatch on one holding-register block that only faulted when the Logix MSG overlapped a Centum write. Stagger the MSG. Lock the PLX32 timeout longer than the Centum TCP keepalive. We also pinned the gateway to a managed port with storm control — a printer job on the same VLAN was enough to trip it.

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