AN2108 Freescale Semiconductor / Motorola, AN2108 Datasheet - Page 22

• Manufacturer Part Number: AN2108
• Description: AN2108 Programming the DSP56307/DSP56311 EFCOP in C Using Taskings Tool Suite
• Manufacturer: Freescale Semiconductor / Motorola

6.2.1 Theory
6.2.2 Implementation
22
Application Examples
key steps involved in performing an FIR filtering task are described in the following subsections, and a
100 sample signal with a 20 tap FIR filter is used in the example code. The State Initialization mode is
enabled.
Figure 11 shows the generic structure of an FIR filter. The output sample at time index k is calculated as a
weighted average of the N most recent input samples, x(k) ... x(k-N+1). This is expressed mathematically
as:
where N is the number of filter coefficients, x(k-i) is the input sample at time index k-i, y(k) is the output
sample at time index k, and w
The implementation of an FIR filter on the EFCOP using DMA for both input to the EFCOP and output
from the EFCOP involves the steps shown in Figure 12. Since the implementation example uses the
Initialization mode, the EFCOP starts filtering after the FDM buffer is filled with the first N data samples.
8. See Section 5, EFCOP Initialization Mode, on page 19 for details on state initialization.
8
x ( k )
Programming the DSP56307/DSP56311 EFCOP in C
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Freescale Semiconductor, Inc.
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Figure 11. FIR Filter Structure
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