When auto-negotiation is 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 local clock generation block (CGB) divider. If a single base data rate is not possible, you can use an additional PLL to generate the required data rates.
|Data Rate (Mbps)||Base Data Rate (Mbps)||Local CGB Divider|
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