Distributed Clock Unit

The Distributed Clock Unit is a hardware/software component embedded within an EtherCAT master chip. It implements the EtherCAT Distributed Clock (DC) mechanism, which provides deterministic, high-precision clock synchronization across all slave devices in an EtherCAT network. This allows slave devices to operate with a common time base, which is essential for coordinated motion control, synchronized data acquisition, and precise event handling in real-time industrial automation systems.

The unit operates by applying principles similar to IEEE 1588 Precision Time Protocol (PTP), adapted for EtherCAT. It measures and compensates for propagation delays across the network, synchronizing local clocks in slave devices to a reference clock (typically the master's clock) with sub-microsecond accuracy. This is achieved through timestamping of telegrams and continuous offset and drift correction.

Typical parameters include a clock accuracy of ±100 ns (per IEC 61158), sync jitter of ±20 ns, configurable distributed clock period from 1 to 1000 μs, support for 1 to 65535 sync nodes, and 2 to 4 independent sync signal output channels. The unit operates over an extended industrial temperature range of -40 to 85 °C (per IEC 60068-2-14), with a supply voltage of 3.3 to 5 V DC and typical power consumption of 0.5 to 1.5 W. It is available in a QFN-48 package (JEDEC MS-026) with a 7×7 mm footprint. Materials include silicon substrate and copper interconnects.

When selecting or verifying this component, confirm model-specific values and standards with the legal manufacturer or supplier. The listed standards serve as procurement references, not as proof of certification or compliance for a specific product. The unit is a component intended for integration into EtherCAT master designs; its performance depends on the surrounding circuit and network configuration.

The Distributed Clock Unit synchronizes clocks across an EtherCAT network by measuring propagation delays between the master and each slave. It timestamps incoming and outgoing telegrams to calculate offset and drift, then adjusts each slave's local clock to match the reference clock. This process repeats continuously to maintain sub-microsecond synchronization, enabling coordinated actions across distributed nodes.