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Enhanced Filter Coprocessor
10.4.3 Filter K-Constant Input Register (FKIR)
The Filter K-Constant Input Register (FKIR) is a 24-bit write-only register for DSP-to-EFCOP
data transfers in adaptive mode where the value stored in FKIR represents the weight update
multiplier. FKIR is accessible only to the DSP core for reads or writes. When adaptive mode is
enabled, the EFCOP immediately starts the coefficient update if a K-Constant value is written to
FKIR. If no value is written to FKIR for the current data sample, the EFCOP halts processing
until the K-Constant is written to FKIR. After the weight update multiplier is written to FKIR, the
EFCOP transfers it to the FMAC unit and starts updating the filter coefficients according to the
following equation:
New_coefficients = Old_coefficients + FKIR * Input_buffer
10.4.4 Filter Count (FCNT) Register
The FCNT register is a read/write register that selects the filter length (number of filter taps).
Always write the initial count into the FCNT register before you enable the EFCOP (that is,
before you set FEN). The number stored in FCNT is used to generate the correct addressing for
the FDM and for the FCM.
Note:
To ensure correct operation, never change the contents of the FCNT register unless the
EFCOP is in the individual reset state (that is, FEN = 0). In the individual reset state
(that is, FEN = 0), the EFCOP module is inactive, but the contents of the FCNT
register are preserved.
23
22
21
11
10
9
FCNT11 FCNT10 FCNT9
Reserved bit; read as 0; write with 0 for future compatibility
=
Bit #
Abbr.
23–12
These bits are reserved and unused. They read as 0; write with 0 for future compatibility.
11–0
FCNT
Filter Count
The actual value written to the FCNT register must be the number of coefficient values minus one.
The number of coefficient values is the number of locations used in the FCM. For a real FIR filter, the
number of coefficient values is identical to the number of filter taps. For a complex FIR filter, the
number of coefficient values is twice the number of filter taps.
10-36
20
19
18
8
7
6
FCNT8
FCNT7
FCNT6
Table 10-6. Filter Count FCNT Register Bits
DSP56311 Reference Manual, Rev. 2
17
16
15
5
4
3
FCNT5
FCNT4
FCNT3
Description
14
13
12
2
1
0
FCNT2
FCNT1
FCNT0
Freescale Semiconductor
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