1G/2.5G/5G/10G Multirate Ethernet PHY Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs

ID 813667
Date 7/08/2024
Public

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3.2.1. Clocking

Clocking requirements:
  • tx_pll_ref_clk signal is the TX path reference clock for the PMA PLL. It is used to generate the serial clock and the parallel data clocks. Altera recommends that you use 156.25 MHz frequency for the tx_pll_ref_clk signal. Altera also recommends using the same clock for rx_cdr_refclk.
  • For 8-bit GMII (MGBASE-T):
    • The GMII 8-bit Adapter generates the gmii8b_tx_clkout clock signal. For 10M, the clock frequency is 2.5 MHz. For 100M (MII, 4-bit interface), the clock frequency is 25 MHz. For 1G and 2.5G (8-bit interface), the clock frequency is 125MHz and 312.5MHz respectively.
    • The hard processor system (HPS) ethernet media access controller (MAC) drives the gmii8b_tx_clkin signal at the same frequency with gmii8b_tx_clkout signal.
    • The refclk frequency for the MRPHY_PLL is 62.5MHz for 1G and 156.25 MHz for 2.5G.
  • For 16-bit GMII (MGBASE-T), transmit is clocked by tx_clkout. The PHY drives this clock to the MAC. The primary clock frequencies for 1G and 2.5G are 62.5 MHz and 156.25 MHz respectively. For 10M and 100M, the primary clock frequency is 62.5 MHz with clock enable.
  • For the USXGMII mode, the MAC drives the xgmii_tx_coreclkin to the PHY with a single clock frequency of 312.5 MHz.
Table 9.  Clocking Specifications
Clock Signals 10M (MII) 100M (MII) 1G (GMII) 2.5G 5G 10G
MGBASE-T (8-bit)
gmii8b_tx_clkin/gmii8b_tx_clkout 2.5 MHz

(4-bit interface)

25 MHz

(4-bit interface)

125 MHz

(8-bit interface)

312.5 MHz

(8-bit interface)

MGBASE-T (16-bit)
tx_clkout 62.5 MHz

(with clock enable)

62.5 MHz

(with clock enable)

62.5 MHz 156.25 MHz
USXGMII (32-bit)
xgmii_tx_coreclkin 312.5 MHz

(with clock enable)

312.5 MHz

(with clock enable)

312.5 MHz

(with clock enable)

312.5 MHz

(with clock enable)

312.5 MHz

(with clock enable)

312.5 MHz
Figure 8. 2.5G, 1G/2.5G (MGBASE-T) Clocking
Figure 9. 10M/100M/1G/2.5G/5G/10G (NBASE-T) Clocking