V-Series Transceiver PHY IP Core User Guide

ID 683171
Date 7/26/2022
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12.1. Deterministic Latency Auto-Negotiation

The Deterministic Latency PHY IP Core supports auto-negotiation. When required, the channels initialize at the highest supported frequency and switch to successively lower data rates if frame synchronization is not achieved.

If your design requires auto-negotiation, choose a base data rate that minimizes the number of PLLs required to generate the clocks required for data transmission. By selecting an appropriate base data rate, you can change data rates by changing the divider used by the clock generation block. The following table shows an example where setting two base data rates, 4915.2 and 6144 Mbps, with the appropriate clock dividers generates almost the full range of data rates required by the CPRI protocol.

Note: You can use PMA Direct mode in the Transceiver Native PHYs for CPRI applications that require higher frequencies. For more information refer to the following documents: