Every Modbus device comes with a register map. It is usually a table in the user manual or a separate PDF that lists all the data points the device makes available — voltages, currents, setpoints, alarms, status bits, and configuration parameters. Reading a register map sounds simple. But it is one of the most common sources of errors… Read More »
OPC UA Pub/Sub is a communication pattern within the OPC UA standard that allows data to flow from publishers to subscribers without requiring a direct connection between them. A publisher sends data to a message broker or network bus. Any number of subscribers receive that data independently. No handshake. No dedicated session. No request-response cycle. This is fundamentally… Read More »
Every Modbus message contains a function code. It is a single byte that tells the slave device what operation to perform — read coils, write registers, or diagnose communication. The Modbus specification defines multiple function codes, but in practice you will use about six of them for 95% of your tasks. The rest are either rarely implemented, vendor-specific,… Read More »
If you work with IEC 61850, you will deal with SCL files. They are the standard way to describe IED capabilities, substation configurations, and communication parameters. But the first thing that confuses most engineers is this: there are six different SCL file types. ICD, SSD, SCD, IID, CID, SED — each with a different purpose, created by a… Read More »
IEC 60870-5-104 (commonly called IEC 104) is the standard protocol for SCADA communication in power utilities, water systems, and other critical infrastructure across Europe, Asia, and the Middle East. It takes the application layer of IEC 60870-5-101 (the serial telecontrol standard) and maps it onto TCP/IP. This gives you the same proven data model — single-point indications, measured… Read More »
IEC 61850 transformed substation automation. It replaced hardwired copper connections with standardized Ethernet-based communication between intelligent electronic devices (IEDs). GOOSE messages trip breakers in under 4 milliseconds. MMS connects IEDs to SCADA systems. Sampled Values stream real-time voltage and current measurements. But this transformation came with a trade-off. By moving protection and control communications onto Ethernet, substations inherited… Read More »
Modbus was built in 1979 for a world where industrial networks were physically isolated. There was no internet, no remote access, and no reason to worry about authentication or encryption. The protocol was designed for reliability and simplicity — not security. That was fine for decades. But today, industrial control systems are increasingly connected to corporate networks, cloud… Read More »
Modbus TCP/IP brings the simplicity of the Modbus protocol onto modern Ethernet networks. Instead of serial cables and RS-485 wiring, you use standard Ethernet infrastructure — switches, routers, and Cat5e/Cat6 cables. The protocol works the same way as Modbus RTU at the application level. You still read holding registers, write coils, and use the same function codes. The… Read More »
Modbus RTU over RS-485 is the most common serial communication setup in industrial automation. It connects PLCs, sensors, drives, meters, and other field devices on a simple two-wire bus. The protocol itself is straightforward. But getting it to work reliably depends on getting the details right — wiring, termination, addressing, baud rate, parity, and register mapping all need… Read More »
Every OPC UA interaction starts with a simple concept: a client asks, a server answers. But beneath that simplicity sits a carefully layered architecture that handles discovery, security, sessions, subscriptions, and more — all defined in the IEC 62541 standard. This guide explains how the OPC UA client-server architecture works from the ground up. Whether you’re developing an… Read More »