The SPI-4.2 Sink core using Static Alignment might fail to go into frame (i.e., SnkOof asserted indefinitely) during a timing-based simulation with Synopsys VCS.
To work around this problem, change the following DCM phase-shift in the UCF file:
For Virtex-5 devices:
INST "<top_instant_name>/U0/clk0/rdclk_dcm0" PHASE_SHIFT = 25;
For Virtex-4 devices:
INST "<top_instant_name>/U0/clk0/rdclk_dcm0" PHASE_SHIFT = 35;
NOTE: The phase-shift setting provided with the SPI-4.2 core in the constraint file is only a place-holder and might not be approriate for hardware operation. For more information on Static Alignment, refer to the SPI-4.2 User Guide (UG153).
This is fixed in v9.2 of the Core released in 11.3
05/04/2009 - Initial Release
04/07/2010 - Added fixed version