CS4399 datasheet(44/111 Pages) CIRRUS

44 / 111 page

DS1113F1

CS4399

4.10 DSD and PCM Mixing

For mobile application, the CS4399 provides a feature for mixing in PCM notification during DSD playback, with the setup

in Table 4-10.

It is assumed that the DSD path has been properly configured for DSD playback, and DSD_AMUTE function is disabled.

During normal DSD playback, the ASP can be shut down. At the PCM notification event, the ASP must be properly

configured to receive PCM samples at 44.1 kHz. After the ASP subclocks are running, set MIX_PCM_PREP to indicate to

the CS4399 that the PCM mixing event is imminent. After 1.6 ms, MIX_PCM_DSD can be safely set to initiate the mixing

process. After the PCM notification mixing is complete, clear both MIX_PCM_DSD and MIX_PCM_PREP at the same

time. If desired, the ASP can be shut down to save power.

When mixing, use both PCM and DSD volume controls to attenuate the signal content on both paths (e.g., at least –6-dB

attenuation on each) to avoid clipping on the mixing product. Use PCM_VOLUMEx to adjust the PCM path and DSD_

VOLUMEx to adjust the DSD path. All the signal path settings apply to both path’s individual settings.

Figure 4-27. PCM and DSD Mixing Signal Flow

4.11 Standard Interrupts

The interrupt output pin, INT, is used to signal the occurrence of events within the device’s interrupt status registers. Events

can be masked individually by setting corresponding bits in the interrupt mask registers. Table 4-11 lists interrupt status

and mask registers. The configuration of mask bits determines which events cause the immediate assertion of INT:

• When an unmasked interrupt status event is detected, the status bit is set, and INT is asserted.

• When a masked interrupt status event is detected, the interrupt status bit is set, but INT is not affected.

Once INT is asserted, it remains asserted until all status bits that are unmasked and set have been read. Interrupt status

bits are sticky and read-to-clear. Once set, they remain set until the register is read and the associated interrupt condition

is not present. If a condition is still present and the status bit is read, although INT is deasserted, the status bit remains set.

To clear status bits set due to the initiation of a block, all interrupt status bits must be read after the corresponding module

is enabled and before normal operation begins. Otherwise, unmasking these previously set status bits causes assertion

of INT.

Interrupt source bits are set when edge-detect interrupts is detected, and they remain set until the register is read and the

condition that caused the bit to assert is no longer present.

Table 4-10. Mixing Configurations Supported by the CS4399

PCM Input Configuration

DSD Input Configuration

I2S or TDM on

ASP

44.1 kHz

Master

DSD on DSD IF

2.8224 or 5.6448 MHz

on DSDCLK

Master

Slave 1

1.The ASP/XSP subclocks and DSDCLK are required to be synchronous.

Slave 1

Master

DoP on XSP

176.4 or 352.8 kHz

Master

Slave 1

DSD

Processor

Interpolation

Filter &

Volume

Control

DoP to

DSD

Engine

ASP

XSP/

DSD Audio

Interface



Multibit



Modulator

PCM

DSD

MIX_PCM_PREP p. 85

MIX_PCM_DSD p. 86

PCM_VOLUME_B p. 87

PCM_VOLUME_A p. 87

DSD_VOLUME_B p. 84

DSD_VOLUME_A p. 84

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