Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
www.xilinx.com
221
UG155 March 24, 2008
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-1
is also applicable.