Hi,

I have a 100 MHz PCI-X core for Xilinx device.
As a part of PCI-X standard the core is also compliant with PCI 33 MHz.


Now I have a problem with the ucf clock frequency constraint.
Since I want it to work in PCI-X 100 MHz I constraint to clock of
100 MHz; but then the PCI 33 MHz logic fail to meet the timing
constraints.

I can identify the PCI 33 MHz critical paths as the path that goes
directly from pad (TRDY#) to a combinatorical logic, and the paths of
PCI-X as the paths that start at IOB registers.

How can I relax the constraints starting at a pad and ending in a CLB
register ?


ThankX ,
NAHUM