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 »
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 »
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 »