Motorola DSP Developer's Kit

max-1c.asm

[yr, yi, index] = mot###_max( X )

Description

This function returns the largest element of input complex vector X and its index

Input/Output

Input: Complex vector X (includes real part Xr and imaginary part Xi)

Output: Complex vector Y (includes real data of the largest element Yr, and the imaginary data of the largest element Yi), and index

Algorithm

#define IN 0
MaxValue = Xr[0]* Xr[0] + Xi[0]* Xi[0];
Yr = Xr[0];
Yi = Xi[0];
Index = 0;
for(i=1; i<size; i++)
{
   Intervalue = Xr[i]* Xr[i] + Xi[i]* Xi[i];
   if(Intervalue > MaxValue)
   {
        MaxValue = Intervalue;
        Yr = Xr[i];
        Yi = Xi[i];
        index = i;
   }
}

Memory & Register

Memory allocations:

X memory:

• Label IN_REAL stores the start address of the real data

Y memory:

• Label IN_IMAG stores the start address of the imaginary data
• Label IN stores the address offset of the input of the complex vector X

Register usage:

• X1stores the address of the real data of the result
• Y1 stores the address of the image data of the result
• R1 stores the address of the index of the result
• R7is used for the number of items in the array

Status Register

The assembly function max-1c.asm does not explicitly set any status registers/bits during the function execution.

Data Size Limit

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

Data Range Limit

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

Precision

In the case of DSP563, precision is 23 bits.

In the case of DSP566, precision is 15 bits.

max-1r.asm

max-2r.asm