TwiddleGenC Block Generates Incorrect Twiddle Factors with Wide Counters

Description

The DSPBA TwiddleGenC block generate twiddle factors to use when building streaming FFTs. For inputs of width 9 bits or less, the block uses a simple lookup table. For inputs that are 10 bits or more wide, the block uses an optimized lookup table (which consumes fewer memory blocks). The twiddle factors generated by the optimized structure are completely incorrect, therefore the TwiddleGenC block does not work correctly with inputs that are more than 9 bits wide.The BFTC block, which contains the TwiddleGenC block, produces incorrect results for FFTs of size more than 512.

Resolution

To workaround this problem use the TwiddleGenCF block. This problem is fixed in DSP Builder v13.1.