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FKIR for K
(n). The EFCOP automatically clears FSCR[FUPD] when the coefficient update is
e
complete.
If the coefficients are to be updated after every input sample, Adaptive mode is enabled by setting
the FCSR[FADP]. In Adaptive mode, the EFCOP automatically sets the FUDP bit after each
input sample is processed. This allows for continuous processing using interrupts that includes a
filter session and a coefficient update session with minimal core intervention.
10.3.3.2.3 Multichannel Mode Option
Multichannel mode is only available in Real operating mode. It allows several channels of data to
be processed concurrently and is selected by setting the FCSR[FMLC]. The number of channels
to process is one plus the number in the FDCH[FDCM] bits. For each time period, the EFCOP
expects to receive the samples for each channel sequentially. This is repeated for consecutive
time periods.
Filtering can be done with the same filter or different filters for each channel by using the
FCSR[FSCO] bit. If FCSR[FSCO] is set, the same set of coefficients are used for all channels. If
FSCO is clear, the coefficients for each filter are stored sequentially in memory for each channel.
10.3.3.2.4 Decimation Option
Decimation can be used with any four of the available FIR filter type modes. It cannot be used in
conjunction with Adaptive and Multichannel modes. Decimation decreases (downsamples) the
sampling rate. The decimation ratio defines the number of input samples per output sample. The
decimation ratio is one plus the number in the FDCH[FDCM] bits. The decimation ratio can be
programmed from 1 to 16.
For Real and Magnitude modes the decimation ratio number of samples must be written to the
FDIR before an output sample is read from the FDOR. For Complex mode, two times the
decimation ratio number of samples (one for the real part and one for the imaginary part of the
input) must be written to the FDIR before two output samples (one for the real part and one for
the imaginary part of the output) can be read from the FDOR. For Alternating Complex mode,
two times the decimation ratio number of samples must be written to the FDIR (one for the real
part and one for the imaginary part of the input) before one output sample (alternating between
the real part and the imaginary part of the output) can be read from the FDOR.
10.3.4 IIR Filter Type
To select the IIR filter type, set the FCSR[FLT] bit and perform the processing shown in Figure
10-5 based on the equation shown here. The EFCOP multiplies each previous output value in the
Freescale Semiconductor
⎛
M
⎜
∑
y n ( )
S w n ( )
=
+
⎜
⎝
j
=
1
DSP56311 Reference Manual, Rev. 2
⎞
⎟
(
)
A
y n j –
⎟
j
⎠
EFCOP Operation
10-11
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