Posts tagged "Reference"
6 articles across the Voltrus blog.
This collection brings together every Reference article published on the Voltrus blog. "EtherNet/IP Port 44818 Explained: TCP, UDP 2222, and Firewall Rules", "DNP3 Class 0, 1, 2, 3 Explained: Event Polling Strategy", "OPC UA Information Model: Nodes, Objects, and the Address Space" — each one is a practical, hands-on guide written for engineers and system integrators. Whether you are choosing between protocols, troubleshooting a connection, or planning an integration, these articles cover the concepts, the trade-offs, and the step-by-step details you need.
EtherNet/IP Port 44818 Explained: TCP, UDP 2222, and Firewall Rules
EtherNet/IP port 44818 explained. TCP 44818 for explicit messaging, UDP 2222 for cyclic I/O, UDP 44818 for ListIdentity discovery. Firewall rules and security.
Read articleDNP3 Class 0, 1, 2, 3 Explained: Event Polling Strategy
DNP3 Class 0, 1, 2, 3 explained. Class 0 is a full snapshot; Classes 1-3 are prioritized event backlogs. How utility masters poll by class to retrieve only what changed.
Read articleOPC UA Information Model: Nodes, Objects, and the Address Space
OPC UA information model explained. Nodes, objects, variables, type system, the address space, references, and companion specifications. How UA self-describes data.
Read articleOPC UA Companion Specifications: How UA Models Real Industries
How OPC Foundation collaborations with industry bodies (VDMA, PLCopen, VDW, BACnet) add typed, domain-specific information models so multi-vendor equipment interoperates without per-vendor register maps.
Read articleModbus Function Codes Explained: FC01–FC06, FC15, FC16 (2026 Reference)
Every standard Modbus function code explained: FC01 read coils, FC03 read holding registers, FC06 write single register, FC16 write multiple. Request/response frame layout, byte order, and when to use each code.
Read articleModbus Addressing Explained: PLC Address vs Protocol Address (No More Off-By-One)
Why Modbus holding register 40001 is protocol address 0. The PLC address vs protocol address off-by-one confusion, the four address ranges, and how to convert between them.
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