Extra Preamble on GMII Receive Interface Due to PPM Frequency Difference

Description

When the parts per million (PPM) frequency difference between the PCS receive clock and the external PHY transmit clock is not zero, the GMII receive interface will receive and extra preamble (0x55) on the gmii_rx_d data bus.

This issue affects all designs that contain GXB transceiver block.

Resolution

This issue has no workaround.This issue is fixed in version 11.1 SP1 of the Triple-Speed Ethernet MegaCore function.