Motorola MPC860 PowerQUICC, User Manual

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36-32 MPC860 PowerQUICC UserÕs Manual MOTOROLA
Part V. The Communications Processor Module
Þlter example consumes 0.55 million clocks per second, which is only 2.2% of the CPM
loading of an MPC860 at 25 MHz.
The Þlter executes three subÞlters each time a new sample arrives, invoking the FIR2
function with a three-iteration count and auto-increment of the input sample pointer after
the last iteration. FIR2 writes the three subÞlter results into the output buffer, which then
feeds into the modulation. Modulation invokes the MOD function with a three-iteration
count. The MOD function automatically increments the sample pointer on each iteration.
Figure 36-37 shows a conceptual view of the Þlter implementation followed by example
code.
Figure 36-37. Core and CPM Implementation of Filter Example
/* Function Descriptors */
typedef struct dsp_fd {
unsigned short status;
unsigned short parameter[7];
} DSP_FD;
#define WRAP 0x2000 /* wrap bit */
#define INTR 0x1000 /* interrupt on completion */
/* define for function opcodes */
#define FIR_2 0x0102 /* FIR2 filter */
#define MOD 0x0008 /* Modulation function opcode */
/* Initialize a static fd chain of 2 functions */
Dual-Port RAM System Memory
Tx Filter FD
Opcode = FIR2
# of Iterations
# of Taps
CoefÞcient Base
In Buffer Size
XYPTR
Out Buffer Size
Modulation FD
Opcode = MOD
# of Iterations
MOD Table Size
MPTR
In Buffer Size
XYPTR
Out Buffer Size
Input Pointer
Output Pointer
MOD Table Pointer
Input Pointer
Output Pointer
CoefÞcient
Table
Input
Buffer
Output
Buffer
MOD
Table
Output
Buffer