read_me.txt

汇编源代码,IIR滤波器

File Name:       iirbiqdf1_012301.zip

File Contents:   read_me.txt
                 filter.h
                 iir.asm
                 iir.bat
                 iir.sta
                 mds_def.h
                 tiir.c      
                 tiir.h
                 timerfrio.dll

Module Name:     iir
Label Name:      __iir
Description:     This program implements a biquad, DF1 form, IIR filter for 1.15 format data and coefficients.
                 The coefficient buffer that is passed should be in the order b2,b1,b0,a2,a1,Bb2,Bb1,Bb0,
                 Aa2,Aa1.......... The value of a0 is unity. The first two elements of the delay line are 
                 x(-2) and x(-1). The rest of delay line buffer must be ordered as y(n-2), y(n-1) for each stage.
                 This program provides valid output only if the number of biquad stages is greater than one 
                 (only for filter order greater than 2). The equation implemented is:

                 y(n) = b0 * x(n) + b1 * x(n-1) + b2 * x(n-2) - a1 * y(n-1) - a2 * y(n-2)

           Note: The coefficients b's and a's generated using MATLAB can be used	as it is. However, the 
                 'a' coefficients have to be negated in some cases where the coefficient generation software 
                 by itself gives negative 'a' coefficients.

     
Registers used:
	
        R0, R1, R2, R3, R6, R7

        I0 -> Address of the input buffer x[]
        I1 -> Address of delay line buffer d[]
        I2 -> Address of coefficient buffer c[]
        I3 -> Address of Output y[]

        P0 -> (No: of input samples+1) / 2
        P1 -> Number of stages
        P2 
        P5 -> Address of delay line buffer

        [SP+12] -> Address of structure s

        Function Prototype :
        void iir(const fract16 x[],fract16 y[],int n,iir_state_fr16 *s);

          x[]  -  input array 
          y[]  -  output array
          n    -  number of input samples(even)
          s    -  Structure of type iir_state_fr16:
        
          typedef struct iir_state_fr16
          {
             fract16 *c,        // coefficients       
             fract16 *d,        // start of delay line
             int k              // no. of bi-quad stages
          } iir_state_fr16;


Computation Time:
   Total execution time for Number of Samples= Ni  & number of biquad stages = B:

   Kernal Cycle Count    :    (Ni/2){4 + ((B-1)*6) + 4}
                         :    3*Ni*B + Ni/2   
   Initialization        :    33 + 7 = 40


   For Ni=64 & B=2
   Total execution time = 456 cycles          

IIR filter code size :	222 bytes	
IIR filter core size :  108 bytes