Networking Interface for Open Programmable Acceleration Engine: Intel® Programmable Acceleration Card with Intel® Arria® 10 GX FPGA

ID 683532
Date 8/05/2019
Public
Document Table of Contents

2.2.2.1. Clocks in 40GBASE-SR4 Mode

The hssi interface provides a set of clocks and locked status flags to support 40GbE MAC/PCS IP. The interface provides 312.5MHz clock sources for both transmit and receive datapaths. The 40-bit interface between the MAC/PHY and HSSI PHY is synchronous to f2a_tx_clk and f2a_rx_clk_ln0 for transmit and receive, respectively. The locked status outputs from the fPLLs in the HSSI PHY can be used by the MAC and related AFU logic as needed. The additional set of 312.5MHz clock sources (e.g., f2a_tx_clkx2, f2a_rx_clkx2_ln0) are phase-aligned replications and would typically not be needed by the MAC/PHY and related AFU logic.