IEEE1722 Real-Time Clock Format - 9.0 English

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

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The IEEE1722 specification defines the avbtp_timestamp field. This is derived by sampling the IEEE802.1 AS Real-Time Clock and converting the low order time to nanoseconds. This conversion is performed in the core and an alternative RTC using the 1722 format. The output produces on the rtc_nanosec_field_1722[31:0] port.

This port contains a 32-bit word representing nanosecond values. Unlike the IEEE802.1 AS nanosecond field (which resets back to zero when it reaches 1 second), the IEEE1722 nanosecond field counts fully to 0xFFFFFFFF before wrapping around. Therefore, the field wraps around approximately every 4 seconds.

If the system is using the IEEE1722 functionality, this port can be sampled to create the avbtp_timestamp field. Otherwise, this port can be ignored.