Editing Source-synchronous (section)

== Implementation Variations ==

In bi-directional data transfer buses, two opposing unidirectional strobes can be sent from each device. Often the strobe is free running in this case. That is, the strobe continues to toggle whether there is data being transferred or not.

Another variation is the sharing of the same bus to transfer the strobe. In this case the strobe can only be transferred by the device that is sending the data and may require transmission of pre-ambles and post-ambles to indicate the start and end of the strobes. (Example: [[DDR2 SDRAM|DDR2]]).

In large [[ASIC]]s or [[Processor (computing)|processors]], multiple strobes and data groups (data bits that are associated to the same strobe) may exist between the same two devices to account for the slightly different PVT variations in different regions of the same die.