Triple-Speed Ethernet IP User Guide: Agilex™ 3 and Agilex™ 5 FPGAs and SoCs

ID 813669
Date 8/04/2025
Public
Document Table of Contents

6.1.4.1. GMII Clock Signals

Table 71.  GMII Clocks
Name I/O Description
rx_clk_125 I 125 MHz receive clock for the RX datapath on MAC side
tx_clk_125 I 125 MHz transmit clock for the TX datapath on MAC side.
rx_clk_62_5 I 62.5 MHz receive clock for the RX datapath on PCS side.

Altera recommends that this clock and rx_clk_125 share the same clock source. This clock must be synchronous to rx_clk_125. Their rising edges must align and must have 0 ppm and phase shift.

tx_clk_62_5 I 62.5 MHz transmit clock for the TX datapath on PCS side.

Altera recommends that this clock and tx_clk_125 share the same clock source. This clock must be synchronous to tx_clk_125. Their rising edges must align and must have 0 ppm and phase shift.

Note:

For 10/100/1000 Ethernet MAC without Internal FIFO Buffers with 1000BASE-X/SGMII 2XTBI PCS and Embedded PMA Signals (GTS) with IEEE 1588v2 variant, rx_clk_125 and rx_clk_62_5 needs to generated using o_rx_clkout2_62p5.

For 10/100/1000 Ethernet MAC without Internal FIFO Buffers with 1000BASE-X/SGMII 2XTBI PCS and Embedded PMA Signals (GTS) with IEEE 1588v2 variant, tx_clk_125 and tx_clk_62_5 needs to generated using o_tx_clkout2_62p5.

For more information about the clock signals, refer to Clocking Scheme of MAC with 2XTBI PCS and Embedded PMA (GTS) .