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SLES100 − DECEMBER 2003
FUNCTIONS AVAILABLE IN THE EXTERNAL DIGITAL FILTER MODE
The external digital filter mode is selected by setting DSD = 0 (register 20, B5) and DFTH = 1 (register 20. B4).
The external digital filter mode allows access to the majority of the PCM1796 mode control functions.
The following table shows the register mapping available when the external digital filter mode is selected, along with
descriptions of functions which are modified when using this mode selection.
B15 B14 B13 B12 B11 B10
B9
0
B8
0
B7
−
B6
−
B5
−
B4
−
B3
−
B2
B1
−
B0
−
Register 16 R/W
Register 17 R/W
Register 18 R/W
Register 19 R/W
Register 20 R/W
Register 21 R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
1
1
1
−
0
1
−
−
−
−
−
−
−
−
−
1
0
−
FMT2 FMT1 FMT0
−
−
−
1
1
REV
−
−
SRST
−
−
0
−
−
OPE
−
DFMS
−
INZD
OS0
PCMZ
0
0
1
−
−
MONO CHSL OS1
0
1
−
−
−
−
−
−
Register 22
R
1
0
−
−
ZFGR ZFGL
NOTE: −: Function is disabled. No operation even if data bit is set
FMT[2:0]: Audio Data Format Selection
Default value: 000
FMT[2:0]
000
Audio Data Format Select
16-bit right-justified format (default)
20-bit right-justified format
24-bit right-justified format
N/A
001
010
Other
OS[1:0]: Delta-Sigma Modulator Oversampling Rate Selection
Default value: 00
OS[1:0]
00
Operation Speed Select
8 times WDCK (default)
4 times WDCK
01
10
16 times WDCK
11
Reserved
The effective oversampling rate is determined by the oversampling performed by both the external digital filter and
the delta-sigma modulator. For example, if the external digital filter is 8× oversampling, and the user selects
OS[1:0] = 00, then the delta-sigma modulator oversamples by 8×, resulting in an effective oversampling rate of 64×.
The 16× WDCK oversampling rate is not available above a 100-kHz sampling rate. If the oversampling rate selected
is 16× WDCK, the system clock frequency must be over 256 f .
S
40
BB [ BURR-BROWN CORPORATION ]
