34
DS1113F1
CS4399
4.7 Filtering Options
7. After properly unmasked (clearing PLL_READY_INT_MASK and PLL_ERROR_INT_MASK), PLL_READY_INT,
and PLL_ERROR_INT are used to monitor if PLL has been successfully started.
8. Turn on the PLL by setting PLL_START.
4.6.2.2 Powering Down the PLL
1. Clear PLL_START to stop the PLL operation.
2. For further power saving, set PDN_PLL to disable the PLL block.
4.7 Filtering Options
To accommodate the increasingly complex requirements of digital audio systems, the CS4399 incorporates selectable
filters in different playback modes. Note that when switching between filter options, the CS4399 output needs to be
powered down in accordance with the sequence specified in
first before applying any filter changes. After
the filter is changed, for audio playback, the CS4399 output must be powered up.
For PCM/TDM mode, the following interpolation filtering options can be selected:
• Fast roll-off and slow roll-off interpolation filter options.
• In each option above, both low-latency and normal phase-compensation filtering options can be used.
• Nonoversampling (NOS) mode is provided, which minimizes the internal digital processing. Once NOS mode is set,
the settings on the above two options are ignored.
The combination of the options results in five different filter combinations. The specifications for each filter can be found
in
, and response plots can be found in
. These filters have been designed to accommodate a variety
of musical tastes and styles. The PCM filter option register (see
) is used to select filter options.
When in octuple-speed mode, the filter options above are not available and the internal digital processing is minimized.
See the specification in
for filter characteristics.
The DSD processor mode uses a decimation-free DSD processing technique that allows for features such as matched
PCM level output, DSD volume control, and 50-kHz on-chip filter.
4.8 Audio Serial Port (ASP)
The independent, highly configurable ASPs and auxiliary serial ports (XSPs) communicate audio data from other system
devices, such as applications processors. Both ports can be configured to support common audio interfaces, TDM/I
2
S and
left-justified (LJ).
ASP supports both PCM and DoP stream playback. XSP can only support DoP stream playback. For DAC playback, only
one port needs to be enabled. Both ports are enabled only in specific application, such as PCM notification mixing with
DSD/DoP content. Details regarding this application setup can be found in
In this section, the reference to both ports is generalized as “xSP” to explain the common settings between the two ports.
4.8.1
Master and Slave Timing
Each serial port can operate as either the master of timing or as a slave to another device’s timing. If xSP_M/S is set, the
serial port acts as a clock master. If xSP_M/S is cleared, the serial port acts as a clock slave.
• In Master Mode, xSP_SCLK and xSP_LRCK are outputs derived from the internal MCLK.
• In Slave Mode, xSP_SCLK and xSP_LRCK are inputs. Although the CS4399 does not generate the interface
timings in Slave Mode, the expected LRCK and SCLK format must be programmed in the same way as in Master
Mode (see
).
• In both modes, the serial port sample rate register (xSP_SPRATE) must be set per audio content before enabling
the serial port.
• When using ASP for PCM playback, the audio serial port sample bit size register (ASP_SPSIZE) must be set per
audio content before enabling the ASP.
