Fir Filter Type; Fir Operating Modes; Real Mode - Freescale Semiconductor DSP56311 User Manual

Enhanced Filter Coprocessor

10.3.3 FIR Filter Type

To select the FIR filter type clear FCSR[FLT] and perform the processing shown in Figure 10-4
based on the equation shown below. The EFCOP takes an input, x(n), from the FDIR, saves the
input while shifting the previous inputs down in the FDM, multiplies each input in the FDM by
the corresponding coefficient, B
places accumulation result, w(n), in the FDOR. This is done for each sample input to the FDIR.
FDIR

10.3.3.1 FIR Operating Modes

There are four operating modes available with the FIR filter type:
Real
Complex
Alternating complex
Magnitude mode.

10.3.3.1.1 Real Mode

Real mode performs FIR type filtering with real data and is selected by clearing both FOM bits in
the FCSR. One sample, the real input, is written to the FDIR, and the EFCOP processes the data.
Then one sample, the real output, is read from the FDOR. Four options are available with the real
FIR filter type: coefficient update, adaptive mode, multichannel mode, and decimation. The first
10-8
N
∑
w n ( )
=
i = 0
, stored in the FCM, accumulates the multiplication results, and
i
FDM
x(n)
x(n – 1)
x(n – 2)
x(n – N)
Figure 10-4. FIR Filter Type Processing
DSP56311 Reference Manual, Rev. 2
( )
B x n i –
i
FCM
B
0
B
1
B
2
B
N
FDOR
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