Every ASDU (Application Service Data Unit) in IEC 60870-5-104 contains a Type ID — a single byte that defines what kind of data the message carries. It tells the receiving station whether the message contains a single-point indication, a measured value, a command, a counter, or a system message. The Type ID is the first byte of every… 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 60870-5-104 runs over TCP/IP. The port number defines where the controlled station (RTU or IED) listens for incoming connections from the controlling station (SCADA master). Two ports are used in practice: Getting the port wrong means no connection. Leaving it unprotected means your SCADA system is exposed. This guide covers everything about IEC 104 ports — from… Read More »
IEC 60870-5-104 (IEC-104) is one of the most widely used telecontrol protocols in electrical power systems. It plays a central role in communication between substations, RTUs, and control centers, especially in transmission and distribution SCADA systems. IEC-104 is reliable, efficient, and well understood by utilities worldwide. However, when the protocol was originally designed, cybersecurity was not a primary… Read More »
The Application Service Data Unit (ASDU) is the core of the IEC 60870-5-104 communication protocol. It defines how information is represented and exchanged between a controlling station (SCADA master) and controlled stations such as RTUs or IEDs. If the Application Protocol Data Unit (APDU) is the message envelope, the ASDU is the payload — carrying the actual telemetry… Read More »
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 »
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 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 »