Implementing IIR/FIR Filters

1 COEFF ident 1,0
2 include 'head2.asm'
3
4 page 132, 66, 0,10
5 pt cex, mex
6
7 ; This program implements an IIR filter in cascaded canonic sections
8 ; The coefficients of each section are scaled for cascaded canonic sections
9
10
11 00FFFF datin equ $ffff ;location in Y memory of input file
12 00FFFF datout equ $ffff ;location in Y memory of output file
13 00FFF0 m_scr equ $fff0 ;sci control register
14 00FFF1 m_ssr equ $fff1 ;sci status register
15 00FFF2 m_sccr equ $fff2 ;sci clock control register
16 00FFE1 m_pcc equ $ffe1 ;port c control register
17 00FFFF m_ipr equ $ffff ;interrupt priority register
18 000140 xx equ @cvi(20480/64*1.000)) ;timer interrupt value
19 FFD8F1 m_tim equ -9999 ;board timer interrupt value
20 000003 nsec equ 3 ;number of second order sectiona
21 include 'cascade2.asm'
22 ;
23 ; This code segment implements cascaded biquad sections in canonic form
24 ;
25
26 cascade2 macro nsec
27 m ;
28 m ;assumes each section's coefficients are divided by 2
29 m
30 m mpy y0,y1,a x:(r0)+,y0 y:(r4)+,y0 ;x0=1st section w(n-2),y0=a12/2
31 m do #nsec,_ends ;do each section
32 m mac x0,y0,a x:(r0)-,x1 y:(r4)+,y0 ;x1=w(n-1) ,y0=ai1/2
33 m macr x1,y0,a x1,x:(r0)+ y:(r4)+,y0 ;push w(n-1) to w(n-2),y0=bi2/2
34 m mac x0,y0,a a,x:(r0) y:(r4)+,y0 ;push w(n) to w(n-1),y0=bi1/2
35 m mac x1,y0,a x:(r0)+,x0 y:(r4)+,y0 ;get this iter w(n),y0=bi0/2
36 m mac x0,y0,a x:(r0)+,x0 y:(r4)+,y0 ;next iter:x0=w(n-2),y0=ai2/2
37 m _ends
38 m endm
Figure 6-7 COEFF.ASM File Generated by MGEN for Example Design andCascaded Canonic
Implementation (Sheet 1 of 4)
6-10 MOTOROLA