# DCM Linklayer Ref Clock mode

In this mode the Real-time Ethernet Driver should provide the time base for the cyclic frames. `EC_LINKIOCTL_GETTIME` will be called during the DC initialization to initialize the DC related registers of the DC SubDevices and during the SubDevice transition PREOP to SAFEOP to start the DC SYNC signals if needed.

`EC_LINKIOCTL_GETTIME` should return the current 64 bits value in nanoseconds of a time counter running continuously.

During the call to EcLinkSendFrame, the Real-time Ethernet Driver should insert the send time of the frame following the instruction given by `EC_T_LINK_FRAMEDESC::wTimestampOffset` and `EC_T_LINK_FRAMEDESC::wTimestampSize` of the parameter pLinkFrameDesc. A value of 0 means that no time stamp should be inserted.