Cirrus-logic EP93xx Uživatelský manuál stáhnout pdf (Strana 79)

100

101

DS785UM1 3-9

MaverickCrunch Co-Processor

EP93xx User’s Guide

loop

cfmul32 c0, c0, c3 ; c0 <= c0 * 5

cfsub32 c0, c0, c2 ; c0 <= c0 - 1

cfcmp32 r15, c0, c1 ; c0 < 10 ?

blt loop ; yes

cfstr32 c0, [r0, #0x0] ; no, store result

3.2.2 Example 2

The following function performs an FIR filter on the given input stream. The variable “data”

points to an array of floating point values to be filtered, “n” is the number of samples for which

the filter should be applied, “filter” is the FIR filter to be applied, and “m” is the number of taps

in the FIR filter. The “data” array must be “n + m - 1” samples in length, and “n” samples will

be produced.

3.2.2.1 C Code

void

ComputeFIR(float *data, int n, float *filter, int m)

{

int i, j;

float sum;

for(i = 0; i < n; i++)

{

sum = 0;

for(j = 0; j < m; j++)

{

sum += data[i + j] * filter[j];

}

data[i] = sum;

}

3.2.2.2 MaverickCrunch Assembly Language Instructions

ComputeFIR

mov r1, r1, lsl #2 ; n *= 4

mov r3, r3, lsl #2 ; m *= 4

outer_loop

mov r12, r3 ; j = m * 4

cfsub64 c0, c0, c0 ; int_sum = 0;

cfcvt32s c0, c0 ; sum = float(int_sum);

inner_loop

cfldrs c2, [r0], #4 ; c2 = *data++;

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