The DSP_FOLDING_FASTCLOCK attribute tells the tool which port should become the new faster clock when using DSP folding.
The values for DSP_FOLDING_FASTCLOCK are:
•"yes": The tool will use this port as the one that is connects for the new clock.
•"no": The tool will not use this port.
DSP_FOLDING_FASTCLOCK is supported in RTL only. Place this attribute only on a port or a pin.