Category Archives: Communication Protocols

DNP3 IIN (Internal Indications) Bits Meaning & SCADA Troubleshooting Guide

In Distributed Network Protocol (DNP3), the Internal Indications field—commonly known as IIN—plays a fundamental role in real-time SCADA diagnostics. Whether you’re troubleshooting substation RTUs, assessing communication integrity, or analyzing unsolicited events, DNP3 IIN bits provide the device’s internal status and operational health. This article explains DNP3 IIN bits in depth, their function in DNP3, how Wireshark displays them,… Read More »

How IEC 60870-5-104 Works Over Ethernet — Complete Technical Guide

The IEC 60870-5-104 (IEC 104) protocol is one of the most important standards for modern SCADA and telecontrol systems.It extends the earlier IEC 60870-5-101 serial protocol by enabling communication over Ethernet and TCP/IP networks, allowing utilities and industries to operate over LAN, WAN, or even public IP networks with reliability and scalability. This article explains — in plain… Read More »

Adjusting Timeout Values (t0–t3) in IEC 60870-5-104 — Complete Guide

Reliable communication in IEC 60870-5-104 depends heavily on properly tuned timeout parameters. The standard defines several timing constants — t0, t1, t2, and t3 — which control connection setup, data acknowledgment, and link supervision between the controlling station (master) and the controlled station (slave/RTU). Misconfigured timeouts can cause link resets, delayed data updates, or even total communication failure.… Read More »

IEC 60870-5-104 Time Synchronization (CP56Time2a) — Complete Technical Guide

IEC 60870-5-104 is one of the most widely used SCADA communication protocols in power and industrial automation. One of its most critical yet misunderstood components is time synchronization, achieved using the CP56Time2a format. Accurate time coordination across remote terminal units (RTUs), intelligent electronic devices (IEDs), and control centers ensures that every event, command, and alarm can be correctly… Read More »

Balanced and Unbalanced Transmission in IEC 60870-5-101

In the realm of Supervisory Control and Data Acquisition (SCADA) systems, the IEC 60870-5 protocol suite is a fundamental standard for telecontrol and remote communication in power systems and industrial automation. One of the core technical distinctions within the IEC 60870-5-101 profile is between balanced and unbalanced transmission modes. These modes define how communication is initiated and managed… Read More »

What is DNP3 Protocol?

The DNP3 protocol — short for Distributed Network Protocol version 3 — is a robust and reliable communication standard primarily used in SCADA (Supervisory Control and Data Acquisition) systems. It was designed to enable efficient, secure, and interoperable communication between control systems (master stations) and remote field devices such as RTUs (Remote Terminal Units) and IEDs (Intelligent Electronic… Read More »

Modbus RTU vs Modbus TCP/IP — Frame Structure and Key Differences

Modbus is one of the most widely used communication protocols in industrial automation and control systems. Originally designed for serial networks, Modbus evolved to work seamlessly over Ethernet and IP networks, creating two common variants — Modbus RTU and Modbus TCP/IP. Although both use the same core data model and function codes, they differ in frame structure, transmission… Read More »