RM0020 datasheet(61/69 Pages) STMICROELECTRONICS

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RM0020

Performance

61/69

The number of clock cycles for third function call of the frac16/frac32 FFTs without scaling is

the same as for respective float FFT plus N/8.

The clock cycles include bit reversing by bitrev_table_16bit and FFT computation by fft_quad_frac32 function. w_table in

internal flash, seed_table in internal flash.

N is FFT length.

Table 37.

Radix-2 complex to complex frac32 in-place FFT, scaling on(1)

N(2)

First function

call [clock

cycles]

Second function

call [clock

cycles]

Third function

call [clock

cycles]

Improvement to

C function [-]

IPC

[-]

128

6763

6270

6261

0.98

512

32312

31060

31043

0.99

2048

156208

151037

149960

0.99

The clock cycles include bit reversing by bitrev_table_16bit and FFT computation by fft_quad_frac32 function and

fft_radix2_last_stage_frac32 function. w_table in internal flash, seed_table in internal flash.

N is FFT length.

Table 38.

Real to complex float in-place FFT (N odd power of two)(1)

N(2)

First function

call [clock

cycles]

Second function

call [clock

cycles]

Third function

call [clock

cycles]

Improvement to

C function [-]

IPC

[-]

128

3659

3258

3233

2.3

0.97

512

16522

15384

15251

2.3

0.98

2048

76073

72880

71331

2.2

0.99

The clock cycles include bit reversing by bitrev_table_32bit and FFT computation by fft_radix4_float function and

fft_real_split_float function. w_table in internal flash, seed_table in internal flash, wa_table and wb_table in internal flash.

N2_REALPART set to 0.

N is FFT length.

Table 39.

Real to complex float in-place FFT (N even power of two)(1)

N(2)

First function

call [clock

cycles]

Second function

call [clock

cycles]

Third function

call [clock

cycles]

Improvement to

C function [-]

IPC

[-]

256

8288

7615

7593

2.1

0.98

1024

37929

35826

35607

2.0

0.99

4096

176668

173279

172939

1.9

0.95

The clock cycles include bit reversing by bitrev_table_32bit and FFT computation by fft_quad_float function,

fft_radix2_last_stage_float function and fft_real_split_float function. w_table in internal flash, seed_table in internal flash,

wa_table and wb_table in internal flash. N2_REALPART set to 0.

N is FFT length.

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