clocks from mezzanine to carrier not used in ascending order
Rules 5.21 and 5.22 in the FMC standard (version Revised Feb 2010) indicate that clks[0..3] should be assigned in ascending order. It is indicated that this should be done regardless of if the CLK_DIR pin is connected or not. This would only apply to high pin count connecters, however it is assumed that this practise should be carried out for low pin count connecters as well.
In the design CLK1 is used before CLK0.