Datasheet

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SLES071B − MARCH 2003 − REVISED NOVEMBER 2006
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19
External Digital Filter Interface and Timing
The PCM1791A supports an external digital filter interface comprising a 4-wire synchronous serial port, which allows
the use of an external digital filter. External filters include the Texas Instruments DF1704 and DF1706, the Pacific
Microsonics PMD200, or a programmable digital signal processor.
In the external DF mode, LRCK (pin 1), BCK (pin 2), DATA (pin 3), and MUTE (pin 4) are defined as WDCK, the word
clock; BCK, the bit clock; DATAL, the L-channel data; and DATAR, the R-channel data, respectively. The external
digital filter interface is selected by using the DFTH bit of control register 20, which functions to bypass the internal
digital filter of the PCM1791A.
Detailed information for the external digital filter interface mode is provided in the APPLICATION FOR EXTERNAL
DIGITAL FILTER INTERFACE section of this data sheet.
Direct Stream Digital (DSD) Format Interface and Timing
The PCM1791A supports the DSD format interface operation, which includes out-of-band noise filtering using an
internal analog FIR filter. For DSD operation, SCK (pin 5) is redefined as BCK, DATA (pin 3) as DATAL (left-channel
audio data), and LRCK (pin 1) as DATAR (right-channel audio data). BCK (pin 2) must be forced low in the DSD mode.
The DSD format (DSD mode) interface is activated by setting the DSD bit of control register 20.
Detailed information for the DSD mode is provided in the APPLICATION FOR DSD FORMAT (DSD MODE)
INTERFACE section of this data sheet.
TDMCA Interface
The PCM1791A supports the time-division-multiplexed command and audio (TDMCA) data format to enable control
of and communication with a number of external devices over a single serial interface.
Detailed information for the TDMCA format is provided in the TDMCA INTERFACE FORMAT section of this data
sheet.