Timestamping Logic - 9.0 English

Tri-Mode Ethernet MAC LogiCORE IP Product Guide (PG051)

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9.0 English
Note: TEMAC supports IEEE 1588 timestamping.

Whenever a PTP packet, used with the Precise Timing Protocol (PTP), is transmitted or received (see Precise Timing Protocol Packet Buffers), a sample of the current value of the RTC is taken and made available for the software drivers to read. The hardware makes no distinction between frames carrying events or general PTP messages (as defined in IEEE 802.1AS). It always stores a timestamp value for Ethernet frames containing the Ethertype specified for PTP messages.

This timestamping of packets is a key element of tight timing synchronization across the AVB network wide RTC, and these samples must be performed in hardware for accuracy. The hardware in this core therefore samples and captures the local nanoseconds RTC field for every PTP frame transmitted or received. These captured timestamps are stored in the Precise Timing Protocol Packet Buffers alongside the relevant PTP frame, and are read and used by the PTP software drivers.