TX FIFO

The Tx FIFO performs these functions:
  • Separates the soft MAC clock and the SGMII PCS internal clock. The MAC clock and PCS clock must come from the same clock source with different phase shifts.
  • Performs data duplication when the MAC speed is 10 MHz or 100 MHz.

For 10 MHz speeds, the MAC interface runs at 0.625 MHz and each data repeats 100 times. The PCS logic after the TX FIFO consistently runs at 62.5 MHz.