42 lines
876 B
Plaintext
42 lines
876 B
Plaintext
|
/*
|
||
|
|
* iir.dsp -- ADSP-2191 IIR biquad filter for open21xx.
|
||
|
|
* Based on Analog Devices application note.
|
||
|
|
*/
|
||
|
|
.section/PM program0;
|
||
|
|
.global _start;
|
||
|
|
_start:
|
||
|
|
/* Setup */
|
||
|
|
i0 = 0x0100; /* delay line */
|
||
|
|
i1 = 0x0200; /* input */
|
||
|
|
i2 = 0x0300; /* output */
|
||
|
|
i4 = 0x0400; /* coefficients (PM) */
|
||
|
|
l0 = 4; /* 2 * biquad_secs */
|
||
|
|
l4 = 8; /* 4 coeffs per biquad * 2 */
|
||
|
|
m0 = 1;
|
||
|
|
m1 = 1;
|
||
|
|
m3 = -1;
|
||
|
|
m4 = 1;
|
||
|
|
|
||
|
|
se = 0;
|
||
|
|
cntr = 256;
|
||
|
|
do _filtering until ce;
|
||
|
|
mx0 = dm(i1,m3);
|
||
|
|
my0 = 0x2000;
|
||
|
|
cntr = 2;
|
||
|
|
mr = mx0*my0(su), mx0 = dm(i0,m3), my0 = pm(i4,m4);
|
||
|
|
do _quads until ce;
|
||
|
|
mr = mr+mx0*my0(ss), mx1 = dm(i0,m3), my0 = pm(i4,m4);
|
||
|
|
mr = mr+mx1*my0(ss), my0 = pm(i4,m4);
|
||
|
|
sr = ashift mr1 (hi), my1 = pm(i4,m4);
|
||
|
|
mr = mr+mx0*my0(ss), mx0 = dm(i0,m0), my0 = pm(i4,m4);
|
||
|
|
_quads:
|
||
|
|
dm(i0,m3) = sr1, mr = mr+mx1*my1(ss);
|
||
|
|
_filtering:
|
||
|
|
dm(i2,m3) = mr1;
|
||
|
|
rts (db);
|
||
|
|
nop;
|
||
|
|
nop;
|
||
|
|
|
||
|
|
_halt:
|
||
|
|
jump _halt;
|