Motorola MSC8101 ADS User's Guide download pdf (Page 182)

9-6 MSC8101 User’s Guide

Enhanced Filter Coprocessor (EFCOP)

9.2.3 Alternating Complex Mode

Alternating Complex mode performs FIR type filtering with complex data providing

alternating real and complex results based on the following equations:

where H(n) is the coefficients, D(n) is the input data, and F(n) is the output data at time n.

For every two samples (the real part followed by the imaginary part of the input) written to

the FDIR, one sample (alternating between the real part and the imaginary part of the

output) is read from the FDOR.

Alternating Complex mode is selected by writing 10 to FCTL[10–11]:FOM bits. When

Alternating Complex mode is used, the number written to the FCNT register should be

twice the number of filter coefficients minus one, (2*filter length) –1. Also, the

coefficients should be stored in the FCM with the real part of the coefficient in the

memory location preceding the location holding the imaginary part.

9.2.4 Magnitude Mode

Magnitude mode calculates the magnitude of an input signal using the following equation:

where D(n) is the input data and F(n) is the output data at time n. For each sample (the real

input) written to the FDIR, one sample (the real magnitude of the input signal) is read

from the FDOR. Magnitude mode is selected by setting both FCTL[10–11]:FOM bits. In

Magnitude mode, the number written to the FCNT register should be the number of data

samples to compute the magnitude of minus one, and the value in the FCBA register is

ignored.

9.2.5 Data and Coefficient Initialization

Before the first sample can be processed, the filter must be initialized, meaning that the

input samples for times before n = 0 (assuming that time starts at 0) must be loaded into

the FDM. The number of samples needed to initialize the filter is the number of filter

coefficients.

Re F n

even

()()Re H i()()Re D n i–()()⋅ Im H i()()Im D n i–()()⋅–

i 0=

N 1–

∑

Im F n

odd

()()Re H i()()Im D n i–()()⋅ Im H i()()Re D n i–()()⋅+

i 0=

N 1–

∑

Fn() Dn i–()

i 0=

N 1–

∑

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Motorola MSC8101 ADS User's Guide Page 182

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