UM0304

Block FIR 16-bit filter

9/19

3

Block FIR 16-bit filter

3.1

Description

This function computes a direct-form real FIR filter using the coefficients stored in vector h[]

using a simple Block FIR technique, and moves delay line. The input sequence needs to be

start with (T -1) zeros. This is a 16-bit fixed-point implementation. Reference [1] may be

used to explore more about FIR filters.

The user needs to organize the output buffer for y[N] and needs to design the filter taps h[T]

and organize the coefficients in reverse order. The users also need to scale the input x[M]

and filter taps h[T] to avoid overflow.

This function may be called by C or Assembly function(s).

3.2

Function

typedef struct coef{

short *h;

unsigned int m;

}nh;

int fir_16by16_arm9e(int y[], short x[],

sx *p, int N);

nh p;

p.h = h;

p.M = T;

3.3

Arguments and variables

●

h[T] = filter coefficient vector with T number of taps, an integer multiple of 6

●

T = number of filter coefficients (taps), an integer multiple of 6

●

N = filter length or vector length for output

●

x[M] = filter input vector with total M samples, i.e., (M = N + T - 1)

●

y[N] = filter output vector with total N samples

3.3.1

Calling the function from C

Set the arguments and variables as appropriate in C main program and call the function.