DP83640 Synchronous Ethernet Mode: Achieving Sub-nanosecond Accuracy in PTP Applications

Synchronous Ethernet at 100 Mb/s, a feature unique to the National Semiconductor DP83640, enables very accurate synchronization between IEEE 1588 Precision Time Protocol (PTP) systems connected via Ethernet. Using this feature, it is possible to maintain sub-nanosecond master to slave synchronization precision in PTP applications operating within required network topological constraints. It is also possible to generate a slave node clock output which is locked and aligned to the Master PTP clock. This application note first provides a summary of empirical results found when master to slave node synchronization is measured with Synchronous Ethernet mode enabled. Background information is then provided describing the operation of and topological constraints associated with Synchronous Ethernet mode. Typical applications are then described, followed by empirical data which clearly demonstrates the accuracy potential of using Synchronous Ethernet mode. This application note is applicable to the following products: