Triple-Speed Ethernet Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs

ID 813669
Date 4/01/2024
Public

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7.2. Clocking Scheme of MAC with 2XTBI PCS and Embedded PMA (GTS)

The following is the clocking scheme of the design that contains MAC with 2XTBI and Embedded PMA (GTS):
  • 2XTBI PCS runs on 125 MHz and 62.5 MHz clocks while the same 125 MHz clock is used by MAC.
  • The 125 MHz and 62.5 MHz clocks must be synchronous, in which their rising edges must align and must have 0 ppm and phase shift.
  • The GTS Direct PHY is the embedded PMA in this variant. The tx_clkout and rx_clkout on the GTS Direct PHY are used as clock sources for 2XTBI PCS tbi2x_tx_clk and tbi2x_rx_clk.
  • Logic is implemented in the PCS block for clock rate matching by default regardless whether the ENABLE_SGMII option is selected. Therefore, the 125 MHz and 62.5 MHz clocks do not need to be at 0 ppm in comparison with tx_clkout and rx_clkout, which are usually provided by Embedded PMA (GTS).
  • The GTS Direct PHY Transceivers are driven by the 156.25 MHz clock.
  • The reference clock input to the GTS Direct PHY Transceivers, tx_pll_refclk and rx_cdr_refclk, should be driven by the 156.25 MHz external clock.
  • i_pma_cu_clk frequency runs at 250Mhz and it comes from the GTS Reset Sequencer block.
Table 76.  Clock Signals Visible at Top-Level DesignClock signals that are visible at the top-level design for each possible configuration.
Clocks Configurations 12
MAC and 2XTBI PCS with Embedded PMA (GTS)

PMA Clocking Mode

clk Yes
reg_clk No
ff_tx_clk Yes
ff_rx_clk Yes
tx_clk_125 Yes
rx_clk_125 Yes
tx_clk_62_5 Yes
rx_clk_62_5 Yes
tbi2x_tx_clk No
tbi2x_rx_clk No
tx_pll_refclk_p 13 Yes
rx_cdr_refclk_p13 Yes
i_pma_cu_clk Yes
Figure 57. Clock Connectivity for MAC with 2XTBI PCS and Embedded PMA (GTS)
Notes to Clock Connectivity for MAC with 2XTBI PCS and Embedded PMA (GTS):
  1. Intel® recommends that the rx_clk_125, tx_clk_125, rx_clk_62_5, and tx_clk_62_5 share the same clock source.
  2. Therefore, Intel® recommends you use one IOPLL with two output clocks to get the 125 MHz and 62.5 MHz clocks and connect to both the TX and RX datapaths.
  3. rx_clkout and tx_clkout are output clocks generated by the GTS Direct PHY transceivers and internally connected to tbi2x_rx_clk and tbi2x_tx_clk in the variant MAC with 2XTBI and Embedded PMA (GTS).
  4. The reg_clk clock is internally connected to clk in the variant MAC with 2XTBI and Embedded PMA (GTS).
12 Yes indicates that the clock is visible at the top-level design.

No indicates that the clock is not visible at the top-level design.

13 Clock signals of GTS Direct PHY Transceivers.