When using the v1.7 Integrated Block Wrapper for PCI Express, the following changeis recommended for the GTX port called DFEDLYOVRD. This value isbased on the most recent characterization results and were not incorporated into the latest legacy TRN interface version of the wrapper. The legacy TRN interface is the 1.# version series of the wrapper. These settings are included in the v2.4 AXI4-Steam interface version of the wrapper.
Note, that if an older version of the core is being used, either an earlier v1.# core or v2.# core, the most recent attributes are available in the v2.4 wrapper with the only difference between v1.7 and v2.4 being the below.
In the gtx_wrapper_v6.v[hd] file in the core's generated source director, change the port called DFEDLYOVRD to be tied '0' instead of '1'. The old value is not wrong, but this value will allow for more margin and uses the recommended value for DFE clock delay adjustment based on the Virtex-6 FPGA GTX TransceiversUser Guide (UG366).
For asynchronous clocked links, see (Xilinx Answer 42346) for an alternate PMA_RX_CFG value.
08/11/2011 - Initial Release