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DSP_FD
filters[2]= {
{ FIR_2,P11,P12, É, P17}
,{(WRAP | INTR | MOD),P21,P22, É, P27}
};
void main()
{
*
*
*
/* issue command to CP to start processing the FD chain */
issue_command( START_FD );
*
*
*
}
36.19 DSP Function Execution Times and CPM
Performance Calculation
A DSP functionÕs execution time is directly related to the number of taps and iterations
speciÞed. Table 36-30 lists the execution times for each function, including overhead for
context switching, handling the FD, and initialization.
Function
FIR1
FIR2
FIR3
FIR5
FIR6
IIR
MOD
DEMOD
LMS1
LMS2
WADD
Notes:
Add 1 clock for wrap, 5 clocks for stop, and 4 clocks for interrupt.
i = number of iterations.
k+1 = number of taps.
As seen in Table 36-30, the CPM loading from DSP applications depends on which
functions are called and their parameters. The frequency with which the functions are called
also affects CPM loading.
MOTOROLA
Table 36-30. DSP Function Execution Times
53 + 20 × (i-1) + 1.25 × i × (k+1)
47 + 17 × (i-1) + 3 × i × (k+1)
44 + 14 × (i-1) + 4 × i × (k+1)
44 + 14 × (i-1) + 5 × i × (k+1)
50 + 20 × (i-1) + 3 × i × (k+1)
44 + 11 × i
44 + 7 × i
47 + 14 × i
42 + 7 × (k+1)
42 + 7 × (k+1)
46 + 7 × i
Chapter 36. Digital Signal Processing
Part V. The Communications Processor Module
Execution Time
36-33
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