General Description: After I run a timing analysis, the timing report lists the following output path delays for an LVDS pair:
For the P side: Tiockp = 1.763 ns
For the N side: Tdiffout + net + Tiodifoi = 2.839 + 0.0 + 1.195 = 4.034
This indicates a skew of 2.271 ns for this differential LVDS signal. Is this correct?
The Virtex-II and Virtex-II Pro speed files were incorrect--the differential pairs and the skew should be very small. To work around this issue, use the P side value as the clock-to-out for both sides.
This problem is fixed in the latest 5.1i Service Pack, available at: http://support.xilinx.com/support/techsup/sw_updates The first service pack containing the fix is 5.1i Service Pack 1. The first Virtex-II speed file containing the fix is version 1.113 The first Virtex-II Pro speed file containing the fix is version 1.69