F-Tile JESD204B Intel® FPGA IP User Guide

ID 723907
Date 4/23/2024
Public
Document Table of Contents

4.4.5. System PLL Clock

F-tile has three on-board system PLLs. These system PLLs are the primary clock source for hard IP (MAC, PCS, and FEC) and EMIB crossing. When you use the system PLL clocking mode, the blocks are not clocked by the PMA clock and are not dependent on a clock coming from the FPGA core. Each system PLL only generates the clock associated with one frequency interface. For example, you need two system PLLs to run one interface at 1 GHz and one interface at 500 MHz. Using a system PLL allows you to use every lane independently without a lane clock change affecting a neighboring lane. Each system PLL can use any one of the eight FGT reference clocks. System PLLs can share a reference clock or have different reference clocks. Each interface can choose which system PLL it uses, but once selected, it is fixed and not reconfigurable using dynamic reconfiguration.
  • Using system PLL clocking—If system PLL clock/div2 freq > Data Rate/40, data_valid between MAC and Tile asserts periodically to sustain the bandwidth. For TX IP, this is handled via EFIFO. For RX IP, a FIFO is able to sustain the bandwidth.