{ main program for calling real IIR filter
  input, output from DM ports using Timer to create sampling interval
  follows example system described in ADSP-21020 Users Manual
  
  "iirirq.asm"      (requires files "def21020.h", "iircoefs.dat")
  Analog Devices, Inc.  DSP Applications  P.O.Box 9106  Norwood, MA 02062
  Christoph D. Cavigioli ... 25-Apr-1991
}
#include "def21020.h"       { bit placements in ADSP-21020 system registers }
#define SAMPLES 300
#define SECTIONS 3

.EXTERN cascaded_biquad, cascaded_biquad_init;
.GLOBAL coefs, dline;
.PRECISION = 40;
.ROUND_NEAREST;

.SEGMENT /DM    dm_bank0;               { selected by DMS0~ }
.VAR    dline[SECTIONS*2];              { filter delay line thus: }
.ENDSEG;                                { w``, w`, NEXT w``, NEXT w`, ... }

.SEGMENT /DM    dm_bank1;               { selected by DMS1~ }
.VAR    in_channel;                     { memory-mapped I/O port }
.ENDSEG;

.SEGMENT /DM    dm_bank2;               { selected by DMS2~ }
.VAR    out_channel;                    { memory-mapped I/O port }
.ENDSEG;

.SEGMENT /PM    pm_bank1;               { selected by PMS1~ }
.VAR    coefs[SECTIONS*4]="iircoefs.dat";   { a12,a11,b12,b11,a22,a21,... }
.ENDSEG;

.SEGMENT /PM    rst_svc;                { processor RESET service }
        jump begin;
.ENDSEG;

.SEGMENT /PM    tmzh_svc;               { Interval Timer interrupt service }
        jump new_sample;
.ENDSEG;

.SEGMENT /PM    pm_code;                { selected by PMS0~ }

{--- initial setup ---}
begin:  pmwait = 0x0021;                { RAM = zero wait states }
        dmwait = 0xc401;                { RAM = zero wait states 
                                          in_channel = ext. hardware ACK 
                                          out_channel = 5 automatic waits }
        pmbank1=0x000800;               { first address of pm bank 1 (PMS1~) }
        dmbank1=0x00001000;             { first address of dm bank 1 (DMS1~) }
        dmbank2=0x00002000;             { first address of dm bank 2 (DMS2~) }
        l0=0; l1=0; l8=0;
        m1=1; m8=1;
        call cascaded_biquad_init (db); { zero the delay line }
         r0=SECTIONS;
         b0=dline;
        tperiod=199;                    { 100 kHz sampling when CLKIN=20.0 MHz}
        tcount=199;
        bit set imask TMZHI;            { allow interval timer interrupts }
        bit set mode2 TIMEN;            { turn on the interval timer }
        bit set irptl 0;                { RESET doesn`t clear this, you do! }
        bit set mode1 IRPTEN;           { allow interrupts }

{--- main processing loop ---}
wait:   idle;                           { wait for interrupts indefinitely }
        jump wait;                      { after rti, go wait for more }

{--- interrupt service routine which does the filtering ---}
new_sample:
        f8=dm(in_channel);              { simulate this channel with a file }
        call cascaded_biquad (db);      { input=F8, output=F8 }
         b0=dline;
         b8=coefs;
        rti (db);
         dm(out_channel)=f8;            { simulate this channel with a file }
         nop;
.ENDSEG;