Motorola DSP Developer's Kit

diff-c.asm

B = mot###_diff(A,N)

Description

This function performs an N-th order difference between the elements of complex vector A.

Input/Output

Input: Complex vector A, int N (N-th order)

Output: Complex vector B

Algorithm

for ( i = 1; i <= N; i ++ ) {
    for ( j = 1; j <= LengthA - 1; j ++ ) {
        Ar[j] = Ar[j + 1] - Ar[j];
        Ai[j] = Ai[j + 1] - Ai[j];
   }
   -- LengthA;
}
Br = Ar;
Bi = Ai;

Memory & Register

Memory allocation:

• X memory: label IN1_RL points to the start address of the real part of vector A
• Y memory: label IN1_RL points to the start address of the imaginary part of vector A

Register usage:

• R4 stores the start address of vector A
• R0 stores the index of the real part of vector A
• R6 stores the index of the imaginary part of vector A
• R1 stores the index of the real part of vector B
• R5 stores the index of the imaginary part of vector B
• R2 and R3 are used as loop control

Assume M{0...7} = $ffff

Status Register

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

Data Size Limit

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

Data Range Limit

The value of input vector A 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.

Performance Limit

DSP563:

DSP566:

diff-r.asm

fft-r.asm