WM8741
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NORMAL PCM MODE DIGITAL FILTER SELECTION
The 8741 has a number of advanced digital filters that can be selected in all PCM operation modes
(with the exception of 8FS mode).
REGISTER ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
Selects FIR1 filter response
000 = Response 1
R6
Filter Control
06h
[2:0] FIRSEL
000
001 = Response 2
010 = Response 3
011 = Response 4
100 = Response 5
Table 38 PCM Advanced Digital Filter Selection
Five digital filters are available for selection in each of the three OSR modes (low, medium and high
rate) as selected by the OSR bit described in Table 20. It is recommended that the device is muted
before the filter response is changed to prevent noise as the filters are reset from appearing on the
outputs.
For full details of the filter characteristics available in normal PCM mode, please see Table 61 to
Table 63 and Figure 28 to Figure 57.
8FS MODE DIGITAL FILTER
In 8FS mode, the majority of the internal filters are bypassed. In this mode, the data is filtered using
only the filter characteristic described by Table 64 and shown in Figure 58 and Figure 59.
DSD PLUS FILTER SELECTION
The WM8741 has a number of compensation filters that can be selected in DSD Plus mode.
REGISTER ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R6
Filter Control
06h
[4:3] DSDFILT
[1:0]
00
Selects Compensation Filter
response
00 = Response 1
01 = Response 2
10 = Response 3
11 = Response 4
Table 39 DSD Plus Digital Filter Selection
It is recommended that the device is muted before the filter response is changed to prevent noise as
the filters are reset from appearing on the outputs.
Full details of these filters are described in Table 65 and Figure 60 to Figure 67.
DSD DIRECT DIGITAL FILTER
The DSD Direct filter has been designed to provide the minimal of processing to the data with no
decimation, re-quantisation or noise-shaping, in order to preserve the signal integrity as much as
possible. As a result the filter has a wide bandwidth and a very gradual attenuation. It is
recommended that this filter is augmented by analogue post-DAC filtering in order to adhere to the
Scarlet-Book SACD standard.
PP Rev 1.3 October 2007
38
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
