Motorola DSP Developer's Kit

filter-c.asm

[Dr, Di, Zfr, Zfi] = mot###_filter(Br, Bi, Ar, Ai, Cr, Ci, Zir, Zii)

Description

This function filters the data in vector C with the filter described by vectors A and B to create the filtered data D, using Zi as initial conditions

Input/Output

Input: Complex vector A, vector B, vector C, and vector Zi

Output: Complex vector D, and vector Zf

Algorithm

// Zi should be increased by adding one zero value to it. 
// The length of Zi will be equal to Max(LengthA, LengthB)

LengthD = LengthC
for (j = 1; j <= LenghtD; j++ ) {
if ( Abs ( A[1] ) != 1 ) {
D[j] = (A[1]*B[1]*C[j] - A[1]*BI[1]*CI[j]  + AI[1]*B[1]*CI[j]
 + AI[1]*BI[1]*C[j]) / (A[1]*A[1] + AI[1]*AI[1]) + Zi[1];
   DI[j] = (A[1]*B[1]*CI[j] + A[1]*BI[1]*C[j] + AI[1]*BI[1]*CI[j] 
- AI[1]*B[1]*C[j]) / (A[1]*A[1] + AI[1]*AI[1]) + ZiI[1];
for (i = 1; i <= (LengthZi - 1); i ++) {
Zi[i] = (A[1]*B[i+1]*C[j] - A[1]*BI[i+1]*CI[j]  + 
AI[1]*B[i+1]*CI[j] + AI[1]*BI[i+1]*C[j] 
- A[1]*A[i+1]*D[j] + A[1]*AI[i+1]*DI[j]  
- AI[1]*A[i+1]*DI[j] - AI[1]*AI[i+1]*D[j]) / 
(A[1]*A[1] + AI[1]*AI[1]) + Zi[i+1];
ZiI[i] = (A[1]*B[i+1]*CI[j] + A[1]*BI[i+1]*C[j]  + 
AI[1]*BI[i+1]*CI[j] - AI[1]*B[i+1]*C[j] 
- A[1]*A[i+1]*DI[j] - A[1]*AI[i+1]*D[j]  
- AI[1]*AI[i+1]*DI[j] + AI[1]*A[i+1]*D[j]) / 
(A[1]*A[1] + AI[1]*AI[1]) + ZiI[i+1];
}
}
else {
        D[j] = B[1]*C[j] - BI[1]*CI[j] + Zi[1];
        DI[j] = BI[1]*C[j] + B[1]*CI[j] + ZiI[1];
        for (i = 1; i <= (LengthZi - 1); i ++) {
            Zi[i] = B[i+1]*C[j] - BI[i+1]*CI[j] + Zi[i+1] 
- A[i+1]*D[j] + AI[i+1]*DI[j];
                ZiI[i] = BI[i+1]*C[j] + B[i+1]*CI[j] + ZiI[i+1] 
- AI[i+1]*D[j] - A[i+1]*DI[j];

    }

}

}

Memory & Register

Memory allocation:

In X memory:

• X:(#INA) stores the start address of data of vector A
• X:(#INA+LENGTH(A)*2) stores the start address of vector B
• X:(#INA+LENGTH(A)*2 + LENGTH(B)*2) stores the start address of vector ZI

In Y memory:

• Y:(#INB) stores the start address of the vector C data
• Y:(#INB+LENGTH(C)*2) stores the start address of the vector D data

Register usage:

• R2 stores the length of vector MAX(A,B),ZI
• R6 stores the length of vector C
• N7 stores the start address of A
• N2 stores the start address of B
• N6 stores the start address of Zi
• R0 stores the index of A
• R1 stores the index of B
• R3 stores the index of Zi
• R4 stores the index of C
• R5 stories the index of D
• R2 -> N0, N1, N3
• R6 -> N4, N5
• R6 and R7 are used as loop control

Assumes M{0...7} = $ffffff

Status Register

The assembly function filter-c.asm does not set explicitly any status registers/bits during the function execution.

Data Size Limit

The length of vector C can't be larger than the continuous available data memory size.

Data Range Limit

The value of input vectors must be between -1.0 and +1.0.

Precision

In the case of DSP563, the precision is 21 bits.

In the case of DSP566, the precision is 12 bits

Performance Limit

DSP563:

DSP566:

filter-r.asm

ifft-r.asm