300+ SCADA Protocol Articles & Guides
Deep dives on Modbus, DNP3, IEC 60870-5-101/104, IEC 61850, OPC UA, Profinet, MQTT, IEC 62443, and substation automation — written for practicing engineers.
What Is RabbitMQ? The AMQP Message Broker, Explained
RabbitMQ is an open source message broker built on AMQP 0-9-1. See how its routing model works, what the core objects do, and where it fits in real systems.
Modbus TCP Beckhoff TwinCAT: Client and Server Setup
Modbus TCP Beckhoff TwinCAT configuration with TF6250: client function blocks, server XML mapping, licensing by TwinCAT version, and the usual failure points.
Modbus TCP CODESYS: Step-by-Step Configuration
Modbus TCP CODESYS configuration for WAGO, Phoenix Contact, ABB, and Delta PLCs: master and slave setup, channel configuration, and vendor-specific notes.
IEC 61131-3: The Complete Guide to PLC Programming Languages
IEC 61131-3 defines how PLCs are programmed — the languages, data types, function blocks, and software model. A complete guide, current to the 2025 fourth edition.
Modbus TCP ControlLogix Setup in Studio 5000
Modbus TCP ControlLogix setup three ways: the ProSoft MVI56E-MNETC module, AOI socket messaging, and a gateway, with pitfalls and performance notes for each.
Modbus to MQTT: How the Gateway Bridge Works
Modbus to MQTT explained: how a gateway maps registers to topics, builds JSON payloads, and handles reads, writes, QoS and TLS. With a worked example.
XON and XOFF: Software Flow Control Explained
XON and XOFF are the two characters behind serial software flow control. See the DC1/DC3 codes, the pause-resume cycle, and when to use it vs RTS/CTS.
Modbus Parity and Character Format
Modbus parity and character format: data bits, parity, and stop bits for RTU and ASCII, the even-parity default, the two-stop-bit rule, and what parity misses.
Modbus Unit Identifier Explained: Unit ID by Scenario
Modbus Unit Identifier (Unit ID) explained by scenario: direct TCP devices, RTU gateways, multi-port gateways. Value ranges, common defaults, troubleshooting.
Modbus Broadcast Function Codes: Address 0 Explained
Modbus broadcast on address 0: which function codes support it, how serial and TCP differ, turnaround timing, gateway behavior, and when to actually use it.
Modbus Client-Server vs Master-Slave Terminology
Modbus client-server vs master-slave: the 2020 terminology change explained. What stays the same, translation table, and how to read mixed-terminology docs.
Modbus TCP MBAP Header Explained: 7 Bytes Byte by Byte
Modbus TCP MBAP header decoded byte by byte: Transaction ID, Protocol ID, Length, and Unit ID, with a real hex dump, network byte order, and common mistakes.
Modbus TCP Security Explained: TLS on Port 802
Modbus TCP Security explained: TLS on port 802, X.509 certificates, role-based access control, deployment alongside port 502, cipher suites, real setup.
Modbus Byte Order and Word Order: Fix Your 32-Bit Values
Modbus byte order and word order decoded: ABCD, CDAB, BADC, and DCBA. Fix reversed floats and byte-swapped longs, with a five-minute test and vendor defaults.
Modbus TCP S7-1500: MB_CLIENT and MB_SERVER Setup
Modbus TCP S7-1500 setup in TIA Portal: MB_CLIENT, MB_SERVER, and TCON_IP_v4 configured, MB_MODE mapped to function codes, and status codes 8200 and 809B fixed.
EtherCAT Protocol Explained: The Trick That Makes It Fast
EtherCAT protocol explained end to end: processing on the fly, logical addressing and FMMU, frame and datagram structure, four addressing modes, Distributed Clocks, slave internals (FMMU, sync managers, SII), mailbox protocols, over-UDP/IP variant, and the state machine.
Modbus TCP Mitsubishi iQ-R: GX Works3 Setup Guide
Modbus TCP Mitsubishi iQ-R setup in GX Works3: RJ71EN71 module parameters, MODBUS Device Assignment, float byte order, exception codes, and troubleshooting.
Modbus TCP Schneider M340: Unity Pro Setup Guide
Modbus TCP Schneider M340 configuration: CPU embedded port, NOE 0100 and NOC 0401 modules, server and client roles, READ_VAR, WRITE_VAR, and ADDM explained.