User`s guide

FFT
5-178
in Equation 5-2. This parameter has two settings, each
with its advantages and disadvantages, as described in the following table.
Optimizing the Table of Trigonometric Values
When you set the Twiddle factor computation parameter to Table lookup,
you need to set the
Optimize table for parameter. This parameter optimizes
e
j– 2π m 1–()k 1–()M⁄
Twiddle factor computation
Parameter Setting
Sine and Cosine Computation
Method
Effect on Block Performance
Table lookup The block computes and stores
the trigonometric values before
the simulation starts, and
retrieves them during the
simulation. When you generate
code from the block, the
processor running the generated
code stores the trigonometric
values computed by the block,
and retrieves the values during
code execution.
The block usually runs much
more quickly, but requires
extra memory for storing the
precomputed trigonometric
values. You can optimize the
table for memory
consumption or speed, as
described in “Optimizing the
Table of Trigonometric
Values” below.
Trigonometric fcn The block computes sine and
cosine values during the
simulation. When you generate
code from the block, the
processor running the generated
code computes the sine and
cosine values while the code
runs.
The block usually runs more
slowly, but does not need
extra data memory. For code
generation, the block
requires a support library to
emulate the trigonometric
functions, increasing the size
of the generated code.