The Bridge has two EtherCAT connections. The primary port is connected to the primary segment; the secondary port is connected to the secondary segment. The Bridge provides an internal (primary port) and an external (secondary port) time stamp which is used by the Master to adjust the Ref-Clock.
The Bridge device must support the PDO “External Synchronization Status” as defined in the specification ETG.1020 EtherCAT Protocol Enhancements in chapter “21.1.2 Synchronization by a Bridge device”. All slaves according to this specification are supported by the feature pack.
During startup the two segments can be powered-on at different times. That means that there will be an absolute time difference between the two segments. The synchronization process is divided in two parts; DCM and DCX.
- DCM: Synchronize Master timer to slave -> Master-Shift mode
- DCX: Synchronize slaves to bridge device -> Bus-Shift mode