Why is my data lost occasionally when the FIFOs are implemented using block RAM?
This issue can only occur for simultaneous read and write with one word in the FIFO for a synchronous block RAM implementation, and will be fixed in the next version of 'fsl_v20_v2_11_b' in EDK 11.2, scheduled for release later this year.
To work around this issue in EDK 10.1, use the patch included with this Answer Record.
1. Download the patch from:
http://www.xilinx.com/txpatches/pub/applications/misc/ar32322.zip
2. Extract the archive to the local pcores folder of your project, <Project>\pcores\
3. Clean the generated files and re-implement the design.