Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 11/27/2024
Public
Document Table of Contents

5.1.9.3.1. Use Case 1 – Utilize Programmable HPS I/O Delay Feature

Transmit path setup/hold

You should consider for setup and hold time relationship on RGMII transmit path signals TX_CLK to TX_CTL and TXD[3:0]. The Agilex™ 5 SoC HPS dedicated I/O supports programmable Output Chain Delay which can add up to 3 ns of output delay with ~100 ps step increment. The delay added to the EMAC's TX_CLK output when using HPS dedicated I/O can be configured in the HPS Platform Designer IP component IO Delays parameter.

You are recommended to introduce 1.5 to 2 ns I/O delay for TX_CLK to meet the 1 ns PHY minimum input setup/hold time in the RGMII spec, using the HPS programmable I/O delay.

Receive path setup/hold

You should consider for setup and hold time relationship on RGMII receive path signals RX_CLK to RX_CTL and RXD[3:0]. The Agilex™ SoC HPS dedicated I/O supports programmable Input Chain Delay which can add up to 3 ns of input delay with ~100 ps step increment. The delay added to the EMAC's RX_CLK input when using HPS dedicated I/O can be configured in the HPS Platform Designer IP component IO Delays parameter.

You are recommended to introduce 1.5 to 2 ns I/O delay for RX_CLK to meet the HPS EMAC 1 ns setup time, using the HPS programmable I/O delay. Ultimately you want to make sure RX_CLK is in the center of the RX_DATA/RX_CTL data valid window.

Figure 89. TX/RX with HPS Programmable IO Delay Added

For exact HPS Programmable I/O Delay value with relative to device speed grade, refer to the Agilex™ 5 FPGAs and SoCs Device Data Sheet.