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

ID 813669
Date 10/07/2024
Public
Document Table of Contents

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 81.  Clock Signals Visible at Top-Level DesignClock signals that are visible at the top-level design for each possible configuration.
Clocks Configurations 13
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 14 Yes
rx_cdr_refclk_p14 Yes
i_pma_cu_clk Yes
Figure 60. 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. Altera 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, Altera 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).
  5. Altera recommends 156.25 MHz frequency for this clock source when the Agilex™ 5 Reference and System PLL clocks is used to drive the Triple-Speed Ethernet IP only.
13 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.

14 Clock signals of GTS Direct PHY Transceivers.