説明

The SPI-4.2 Lite core may see DCM-related issues in hardware (like failure to lock or incorrect output frequency). The issues only occur in Virtex-4 or Virtex-5 architectures.

ソリューション

This issue is caused by an incorrect setting in the core for the DLL_FREQUENCY_MODE attribute of the DCM. The attribute is currently set to LOW, but should be set to HIGH for Virtex-4 and Virtex-5 cores. 

The workaround is to add the constraint DLL_FREQUENCY_MODE = HIGH in the UCF file for both the Source and Sink Core DCMs. For example: 

INST "pl4_lite_snk_clk0/rdclk_dcm0" DLL_FREQUENCY_MODE = HIGH;  

INST "pl4_lite_src_clk0/tdclk_dcm0" DLL_FREQUENCY_MODE = HIGH; 

This issue will be fixed in the next core release.