Auto-Negotiation

If you need to support 10/100/1,000 M mode auto-negotiation, you need to know the following limitations, and then you can design the layout following the requirements below.
Important: For auto-negotiation mode, only the following PHY models are supported.
  • YT8521DH/DC
  • YT8531DH/DC

Plus, you need to connect the RX_CLK of the PHY to its TX_CLK as shown by the orange lines in the following diagram.

Figure 1. GMAC 10 M/100 M/1,000 M Auto-Negotiation
Layout requirements for GMAC0.
  • The trace length from TX_CLK to RX_CLK cannot exceed 500 mil.
  • The RX and TX trace length cannot exceed 4,300 mil.
  • Match the RXD[3:0] signal group and the RX_CTL and RX_CLK signals with trace length to within 100 mil.
  • Match the TXD[3:0] signal group and the TX_CTL and RX_CLK signals with trace length to within 100 mil.
  • The routing of data and clock lanes should keep a complete reference plane.
Layout requirements for GMAC1.
  • The trace length from TX_CLK to RX_CLK cannot exceed 500 mil.
  • The RX_CLK trace length cannot exceed 4,000 mil. Match the RXD[3:0] signal group and the RX_CTL and RX_CLK signals with trace length to within 100 mil.
  • The TX_CLK trace length is 2,000 mil longer than that of the RX_CLK. Match the TXD[3:0] signal group and the TX_CTL and RX_CLK signals with trace length to within 100 mil.
  • The routing of data and clock lanes should keep a complete reference plane.