LAN9250 datasheet(299/421 Pages) MICROCHIP

299 / 421 page

 2015 Microchip Technology Inc.

DS00001913A-page 299

LAN9250

sages and calculates its own delay. While the end-to-end method is the simplest, it does add burden on the master since

the master must process packets from each slave in the system. This is amplified when boundary clocks are replaced

by transparent clocks. Also, the end-to-end delays must be recalculated if there is a change in the network topology.

Using the peer-to-peer method, packets are exchanged only between adjacent master, slaves and transparent clocks.

Each peer pair calculates the receive path delay. As time synchronization packets are forwarded between the master

and the slave, the transparent clock adds the pre-measured receive path delay into the residence time. The final

receiver adds its receive path delay. Using the peer-to-peer method, the full path delay is accounted for without the mas-

ter having to service each slave. The peer-to-peer method better supports network topology changes since each path

delay is kept up-to-date regardless of the port status.

The PTP implementation consists of the following major function blocks:

• PTP Timestamp

This block provides time stamping and packet modification functions.

• 1588 Clock

This block provides a tunable clock that is used as the time source for all PTP timestamp related functions.

• 1588 Clock Events

This block provides clock comparison-based interrupt generation and timestamp related GPIO event generation.

• 1588 GPIOs

This block provides for time stamping GPIO input events and for outputting clock comparison-based interrupt sta-

tus.

• 1588 Interrupt

This block provides interrupt generation, masking and status.

• 1588 Registers

This block provides contains all configuration, control and status registers.

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