Zakaria El Intissar

I'm an automation and industrial computing engineer with 12 years of experience in power system automation, SCADA communication protocols, and electrical protection. I build tools and write guides for Modbus, DNP3, IEC 101/103/104, and IEC 61850 on ScadaProtocols.com to help engineers decode, analyze, and troubleshoot real industrial communication systems.

Author Archives: Zakaria El Intissar

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 »

Wireshark IEC 60870-5-104 Decoding — Analyze SCADA Communication in Depth

Wireshark is the go-to tool for analyzing communication protocols — and it fully supports IEC 60870-5-104 (commonly known as IEC 104). Whether you’re diagnosing network issues, validating SCADA data, or learning how IEC 104 works, Wireshark provides an unmatched level of visibility into the protocol’s Ethernet, TCP, and ASDU layers. This guide shows you how to capture, decode,… 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 »

Zero-Trust Architecture for SCADA — Securing IEC 60870-5-104 Systems

Modern SCADA systems are no longer isolated. With the rise of remote substations, cloud monitoring, and IP-based protocols like IEC 60870-5-104, the traditional “trusted internal network” model is obsolete. That’s where Zero-Trust Architecture (ZTA) comes in — a cybersecurity framework that assumes no device, user, or network is inherently trustworthy.Instead, every connection must be verified, authenticated, and continuously… 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 »

RS232 vs RS485: Key Differences, Comparison, and Pinout Explained

When comparing RS232 vs RS485, it’s essential to understand that both are serial communication standards — meaning they send data bit by bit over a single communication line. However, RS232 is designed for short, point-to-point connections, while RS485 supports long-distance, multi-device networks using differential signaling. This guide explains the key differences, pin configurations, wiring, and real-world use cases… 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 »

RS-485 Wiring Guide: Best Practices, Installation Steps, and Common Mistakes to Avoid

The RS-485 communication standard is the backbone of many industrial and building automation systems. It allows robust and reliable data transfer across distances of up to 4,000 feet (1,200 meters) using cost-effective twisted pair cabling. This guide provides practical RS-485 wiring recommendations for RS-485 controllers, helping installers and engineers avoid communication failures and ensure long-term system stability. Understanding… Read More »

Python Modbus Libraries Comparison: The Complete 2025 Guide

When working with industrial automation, IoT sensors, or PLC communication, the Modbus protocol remains one of the most widely used standards for device interoperability. Python, with its rich ecosystem and simplicity, has become a go-to language for building Modbus clients, servers, and gateways. But with multiple Python Modbus libraries available — PyModbus, MinimalModbus, pyModbusTCP, Modbus-tk, and others —… Read More »