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

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

3.3.1.2. FGT PMA Configuration Rules for GPON Mode

You ca implemet the upsteam GPON, XG(S)PON, 25G PON, ad 50G asymmetic PON potocols with the F-Tile PMA/FEC Diect PHY Itel® FPGA IP by usig the settigs show below:
  • Set the FGT PMA cofiguatio ules paamete to GPON.
  • Set the Adaptatio mode paamete to maual.
  • Eable the fgt_x_cd_fast_feeze_sel pot.
  • Eable the fgt_x_cd_feeze pot.

To achieve the best FGT RX pefomace whe eceivig the bust mode taffic, you must adhee to the followig guidelies:

  • You must make sue that addesses 0x62000[16] ad 0x62004[12] ae set to 1’b1.
    Note: 0x62000 ad 0x62004 ae the offset addesses fo lae 0.
  • You must tie the fgt_x_cd_fast_feeze_sel sigal to 1’b0.
  • You must asset the fgt_x_cd_feeze sigal whe the bust disappeas ad deasset fgt_x_cd_feeze whe the bust appeas. Fo the timig elatioship betwee the fgt_x_cd_feeze sigal ad busts, efe to the followig coditios:
    • The tasceive iput sigal fgt_x_cd_feeze popagates to *igess*231* with a latecy about 10 s.
    • *igess*231* is the iteal sigal that cotols the CDR feeze o ufeeze logic.
    • It is ecommeded that you alig *igess*231* sigal assetio ad deassetio with the x_seial_data disappeaig ad eappeaig.
    • You ca captue the *igess*231* sigal usig Sigal Tap via the path *__tiles|z*_x*_y*_*__eset_cotolle|x_f_tile_soft_eset_ctl_sip_v1|x_ftile_eset|st_ctl|iflux_igess_diect_231
Table 30.  Timig Impact of *igess*231* ad x_seial_data
Sigal Coditio Ealy Late
Assetio of *igess*231* The CDR may ot tack the tail of the pio data esultig i highe BER. The CDR ca dift i fequecy esultig i a loge lock time o the ext bust.
Deassetio of *igess*231* The CDR ca dift i fequecy esultig i a loge lock time o the ext bust. The stat of the peamble ca be missed esultig i a loge lock time o the cuet bust.
Note: It is acceptable if you caot pefectly alig the *igess*231* sigal with the x_seial_data. The FGT RX CDR ca lock to the icomig bust fast eough withi the peamble duatio to meet the PON-elated specificatios.
  • Duig the idle time (o active bust), the diffeetial voltage at the FGT RX should be 0 istead of a egative value. This is to esue the AC couplig capacito ca quickly chage up to a stable value whe the bust aives.
    • If a optical lie temial (OLT) optical module is coected to FGT RX, the eable squelch should meet the 0 diffeetial voltage equiemet.
    • If the FGT TX is coected to FGT RX, the eable TX electical idle to meet the 0 diffeetial voltage equiemet. Fo PON applicatios with 32-bit PMA width:
      • To eable TX electical idle: set the tx_paallel_data bit[35] ad bit[75] to 1’b1
      • To disable TX electical idle: set the tx_paallel_data bit[35] ad bit[75] to 1’b0
  • You must maually tue the RX EQ paametes: VGA gai, high fequecy boost ad DFE data tap 1.
    Note: Whe the othe paametes ae fixed, a smalle RX iput voltage swig equies a smalle VGA gai value. A lage RX iput voltage swig equies a lage VGA gai value.
  • You may eed to maually tue the CDR gai paametes: popotioal gai ad itegal gai, if the tued RX EQ paametes caot achieve the pefomace you equie.
    • Whe the fgt_x_cd_feeze sigal assets, the itegal path is foze while the popotioal path is still active.
    • Highe gai value fo the popotioal path ad itegal path helps the RX CDR to ealig to the icomig data phase quicke but ca ceate a highe jitte i the pocess.
    • Whe the fgt_x_cd_feeze sigal assets, a highe gai value fo the popotioal path may speed up the diftig pocess ad cause the CDR to be fa away fom the taget phase aligmet.
    • Popotioal gai egiste is: 0x4157C[24:20].
      Note: This is the offset addess fo lae 0.
    • Itegal gai egistes ae: 0x4158C[17:13], 0x41484[14:10], 0x41484[24:20], 0x41488[4:0], 0x41488[14:10], 0x41488[24:20], 0x4148C[4:0], 0x4148C[14:10]
      Note: These ae the offset addesses fo lae 0.
    • A example of optimal settigs fo the CDR gai egistes ae:
      • Popotioal gai value: 0xA
      • Itegal gai value: 0xC
To use the LTR mode whe you select the GPON settig fo the FGT PMA cofiguatio ules paamete, you must adhee to the followig guidelies:
  • Set the Eable fgt_x_cd_set_locktoef pot paamete to O.
  • Set the CDR lock mode paamete to auto.
  • Set egistes 0x41678[27:26] ad 0x41678[29:28] to 2'b11, othewise, the LTR/LTD switchig may fail.
  • Set egistes 0x41580[30] ad 0x41580[31] to 1'b1, othewise, duig LTR mode, the x_paallel_data may be ivalid.