Category Archives: Communication Protocols

What Is a Merging Unit? IEC 61850 Process Bus Explained

A complete reference for substation engineers covering Merging Units — IEC 61869-9 specification, processing delay limits, sample rates, variant codes, SmpSynch values, conformance classes, holdover mode, PTP/1PPS synchronization, procurement template, and field troubleshooting Quick Reference Item Value What it does Digitizes CT/VT signals and publishes Sampled Values on the process bus Standard IEC 61869-9:2016 (replaces 9-2LE guideline) Transport… Read More: What Is a Merging Unit? IEC 61850 Process Bus Explained »

PROFINET Port Numbers Explained: UDP 34962/34963/34964, Ethertype 0x8892, and Firewall Configuration

A complete reference for PROFINET ports — covering UDP 34962 (RT Unicast), UDP 34963 (RT Multicast), UDP 34964 (RPC Context Manager), UDP 49152, the Ethertype 0x8892 for cyclic I/O, MRP Ethertype 0x88E3, firewall rules, and Wireshark filters Introduction PROFINET ports are different from every other industrial protocol. Unlike Modbus (port 502), DNP3 (port 20000), or IEC 104 (port… Read More: PROFINET Port Numbers Explained: UDP 34962/34963/34964, Ethertype 0x8892, and Firewall… »

OPC UA Port Number Explained: TCP 4840, Discovery, and Firewall Configuration

OPC UA uses TCP port 4840 by default. This single port carries everything OPC UA does — discovery, session establishment, reading tags, writing values, subscriptions, method calls, and historical data access. Unlike OPC Classic (which used DCOM with dynamic port allocation and was a firewall nightmare), OPC UA uses one well-known port that works cleanly through NAT, proxies,… Read More: OPC UA Port Number Explained: TCP 4840, Discovery, and Firewall… »

Top 10 Free Modbus Simulators

You’re building a SCADA master, configuring a PLC, or bringing up an HMI — but the field devices aren’t there yet. The meters, VFDs, sensors, and I/O modules are still on order, or they’re sitting at a site you can’t reach. A Modbus simulator fills the gap. It runs on your laptop and answers as if it were… Read More: Top 10 Free Modbus Simulators »

CIP Object Model Explained: Classes, Instances, Attributes, and Services

Every CIP device — whether it is an Allen-Bradley PLC, a variable frequency drive, a remote I/O module, or a safety controller — organizes its data using the same object model. Understanding this model is the key to configuring, programming, and troubleshooting any CIP-based device. CIP (Common Industrial Protocol) does not use register maps like Modbus. Instead, it… Read More: CIP Object Model Explained: Classes, Instances, Attributes, and Services »

PROFINET Conformance Classes Explained: CC-A, CC-B, CC-C (IRT), and CC-D (TSN)

PROFINET is one protocol — not three. But it comes in four conformance classes that define what a device can do, how fast it communicates, and what network infrastructure it needs. Engineers often confuse PROFINET RT, PROFINET IRT, and PROFINET IO as separate protocols. They are not. They are all part of PROFINET IO, defined in IEC 61158… Read More: PROFINET Conformance Classes Explained: CC-A, CC-B, CC-C (IRT), and CC-D… »

PROFINET vs EtherNet/IP: Complete Comparison for Industrial Engineers

PROFINET and EtherNet/IP are the two largest Industrial Ethernet protocols in the world. Together they account for over 60% of all new industrial Ethernet nodes installed each year. Both run on standard Ethernet hardware — same cables, same connectors, same switches. But the similarity ends at the physical layer. Above Layer 2, they use completely different protocol stacks,… Read More: PROFINET vs EtherNet/IP: Complete Comparison for Industrial Engineers »