Rx Elastic Buffers: Depths and Maximum Frame Sizes

R

Virtex-4 FX

Consider the Virtex-4 FX case also illustrated in Figure E-1. The thresholds are different to that of the Virtex-II Pro/Virtex-5 case, but the overall size of the buffer is the same. Instead of the half full point, there are configurable clock correction thresholds. During the interframe gap, clock correction will attempt to restore the occupancy to within these two thresholds.

However, by setting both CLK_COR_MAX_LAT and CLK_COR_MIN_LAT thresholds to the same value, symmetrically between overflow and underflow marks, it is possible to obtain the same figures as per the Virtex-II Pro/Virtex-5 analysis. For this reason, by adjusting the threshold attributes accordingly, Table E-1is also applicable.

Ethernet 1000BASE-X PCS/PMA or SGMII v9.1

www.xilinx.com

221

UG155 March 24, 2008

Page 221
Image 221
Xilinx 1000BASE-X manual Virtex-4 FX, Rx Elastic Buffers Depths and Maximum Frame Sizes