F-Tile Architecture and PMA and FEC Direct PHY IP User Guide

ID 683872
Date 11/04/2024
Public
Document Table of Contents

4.5.1. Guidelines for System PLL Reference Clock

Fo efeece clock, Refclk #i (i = 0 to 9) that ae beig used by system PLL # ( = 0, 1, 2):
  • Whe the paamete Refclk #i is active at ad afte device cofiguatio is set to O, the efclk #i must be active at ad afte device cofiguatio time, o else, the system PLL does ot lock.
  • Whe the paamete Refclk #i is active at ad afte device cofiguatio is set to Off, the efclk #i ca be active afte device cofiguatio time. Afte the efclk #i is active, you eed to asset efclock_eady[] ad e_efclk_fgt_i sigals to idicate system PLL # efeece clock is eady. If you asset the efclock_eady[] o e_efclk_fgt_i sigal befoe the efclk #i becomes active, the system PLL does ot lock ad you have to ecofigue the device.
  • Oce efclk #i is active, it must be stable ad peset thoughout the device opeatio ad must ot go dow.
All efclk #i that ae beig used by system PLLs must have the Refclk #i is active at ad afte device cofiguatio paamete set to the same value. Oly the followig two cases ae suppoted.
  • All system PLL efeece clocks have the Refclk #i is active at ad afte device cofiguatio paamete set to O.
  • O all system PLLs efeece clocks have the Refclk #i is active at ad afte device cofiguatio paamete set to Off.

Whe Refclk #i is active at ad afte device cofiguatio paamete is set to Off, a iteal clock is used to calibate ad cofigue the FPGA device. Due to the low fequecy of the iteal clock, the calibatio ad cofiguatio takes loge to fiish. I additio, afte the system PLL # efeece clock is eady, you must asset the efclock_eady[] ad e_efclk_fgt_i sigals. This flow may ot meet the lik up equiemets fo some IP potocols. You must make sue you desig applicatio is compatible with this flow. Altea ecommeds supplyig a stable ad uig system PLL efeece clock at device cofiguatio, ad eablig the Refclk #i is active at ad afte device cofiguatio paamete.

Fo PCIe itefaces that equie compliace to PCIe lik taiig specificatios, the efeece clock to the system PLL must be available ad stable befoe device cofiguatio begis. You must set the Refclk #i is active at ad afte device cofiguatio paamete i the F-Tile Refeece ad System PLL Clocks Itel® FPGA IP to O ad dive the efeece clock fom a idepedet ad fee uig clock souce. Alteately, if the efeece clock fom the PCIe lik is guaateed to be available befoe device cofiguatio begis, you may use it to dive the system PLL. Oce the PCIe lik efeece clock is alive, it must eve go dow.