Why is the impulse response incorrect for the Multiply Accumulate Filter Architecture with Symmetric Coefficient Structure for an Interpolating filter and targeting a Virtex/-E/-II/-II Pro and Spartan-II/-IIE/-3/-3E/-3A device?
This is due to the limited support for symmetry in the FIR Compiler v2.0 for Spartan-II/-IIE/-3/-3E/-3A and Virtex/-E/-II/-II Pro families. See (Xilinx Answer 24680).
The GUI has been updated in the FIR Compiler v3.0 to automatically turn Off support for symmetry when it is not supported. The limitation has been removed from the FIR Compiler v3.2 and utilization of symmetry will be supported for all families.
See (Xilinx Answer 29138) for a detailed list of LogiCORE FIR Compiler Release Notes and Known Issues.