Motorola MSC8101 ADS User's Guide download pdf (Page 181)

Specifying the Operating Modes for the FIR Filter Type

Enhanced Filter Coprocessor (EFCOP) 9-5

to be from 1 to 64. For each time period, the EFCOP expects to receive the samples for

each channel sequentially. This process repeats for consecutive time periods.

Filtering is performed with the same filter or different filters for each channel using the

FACR[8]:FSCO bit. If this bit is set, the same set of coefficients is used for all channels. If

FACR[8]:FSCO is clear, the coefficients for each channel are stored sequentially in

memory with the beginning address of each coefficient buffer at the next 2

address

(where 2

k-1

≤ filter length ≤ 2

). If the filter length is less than 2

there is a space between

the sequential buffers of 2

minus the filter length.

9.2.2 Complex Mode

Complex mode performs FIR type filtering with complex data based on the following

equations, in which Re is the real part and Im is the imaginary part:

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 written to the FDIR (the real part followed by the imaginary part of

the input), two samples (the real part followed by the imaginary part of the output) are

read from the FDOR.

Complex mode is selected by writing 01 to the FCTL[10–11]:FOM bits. When 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.

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

i 0=

N 1–

∑

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

i 0=

N 1–

∑

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Motorola MSC8101 ADS User's Guide Page 181