1 mono and stereo paths, 2 mixer input attenuation adjustment, Table 11. digital mixer soft ramp rates – Cirrus Logic CS42L73 User Manual
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4.11.1 Mono and Stereo Paths
Notice how
distinguishes between stereo and mono channels; there are buses for the stereo
inputs and the digital mixer’s inputs, outputs, and programmable attenuation mixers are color coded
(green for mono, blue for stereo).
The figure also illustrates how the outputs destined, via their respective ASRCs, for the XSP and VSP can
be configured for normal stereo channeling or to send a mono mix to both stereo channels (as per register
bits XSPO_STEREO and VSPO_STEREO). For details on when to use these controls, refer to section
The mixers that fed the green mono analog outputs have flexible ASP and XSP input source selectors
(refer to register controls ESL_ASP_SEL[1:0]. ESL_XSP_SEL[1:0], SPK_ASP_SEL[1:0], and SPK_
XSP_SEL[1:0]). These selectors are used to either pick one of the stereo inputs or a mono mix of them.
One use of these selectors would be to configure stereo play of the ASP input to the Speakerphone (SPK)
and Speakerphone Line Outputs (SPKLO). The left channel of the ASP would be routed to the SPK and
the right ASP channel would be routed to the SPKLO.
4.11.2 Mixer Input Attenuation Adjustment
Each time a mixer’s input attenuation is adjusted, including the setting or resetting the mute condition (via
register controls “Stereo *_A[5:0]” and “Mono *_A[5:0]”), a soft ramp can selectively (via register control
bit MXR_SFTR_EN) be used to smooth the transition, ensuring no inharmonious artifacts are introduced.
The only exception to the selectivity of soft ramping occurs when an ASRC that feeds the digital mixer
loses lock. In this situation, to prevent unpredictable data from reaching an device output, the ASRC freez-
es its last output value sent to the mixer and the mixer soft ramps the affected inputs to mute.
Soft-ramping logarithmically traverses the digital mixer’s -90 to 0 dB attenuation range according to the
register control MXR_STEP[2:0]. The inaudible steps from/to mute (-
dB) to/from -90 dB occur in a linear
(vs. logarithmic) magnitude manner.
lists mixer soft ramping rates for the nominal and extreme
internal sample rates (Fs) and all MXR_STEP[2:0] configurations.
Table 11. Digital Mixer Soft Ramp Rates
Fs Rate
(kHz)
MXR_STEP[1:0]
Setting
Step Size
(dB)
Step Period
(# Fs period/step)
Soft Ramp Rate
(dB/s)
44.100
000
1/8
1
5,512.5
001
1/4
1
11,025.0
010
1/2
1
22,050.0
011
1
1
44,100.0
100
1/8
4
1,378.1
101
1/8
2
2,756.3
48.000
000
1/8
1
6,000.0
001
1/4
1
12,000.0
010
1/2
1
24,000.0
011
1
1
48,000.0
100
1/8
4
1,500.0
101
1/8
2
3,000.0
50.781
000
1/8
1
6,347.6
001
1/4
1
12,695.3
010
1/2
1
25,390.5
011
1
1
50,781.0
100
1/8
4
1,586.9
101
1/8
2
3,173.8