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DS657F3
41
CS4265
6.9
ADC Input Control - Address 09h
6.9.1
PGA Soft Ramp or Zero Cross Enable (Bits 4:3)
Function:
Soft Ramp Enable
Soft Ramp allows level changes, both muting and attenuation, to be implemented by incrementally ramp-
ing, in 1/8 dB steps, from the current level to the new level at a rate of 1 dB per 8 left/right clock periods.
.
Zero Cross Enable
Zero Cross Enable dictates that signal-level changes, either by attenuation changes or muting, will occur
on a signal zero crossing to minimize audible artifacts. The requested level change will occur after a time-
out period between 512 and 1024 sample periods (10.7 ms to 21.3 ms at 48 kHz sample rate) if the signal
does not encounter a zero crossing. The zero cross function is independently monitored and implemented
for each channel. See
.
Soft Ramp and Zero Cross Enable
Soft Ramp and Zero Cross Enable dictate that signal-level changes, either by attenuation changes or mut-
ing, will occur in 1/8 dB steps and be implemented on a signal zero crossing. The 1/8 dB level change will
occur after a time-out period between 512 and 1024 sample periods (10.7 ms to 21.3 ms at 48 kHz sam-
ple rate) if the signal does not encounter a zero crossing. The zero cross function is independently mon-
itored and implemented for each channel. See
.
6.9.2
Analog Input Selection
(Bit 0)
Function:
These bits are used to select the input source for the PGA and ADC. Please see
6.10
DAC Channel A Volume Control - Address 0Ah
DAC Channel B Volume Control - Address 0Bh
.
7
6
5
4
3
2
1
0
Reserved
Reserved
Reserved
PGASoft
PGAZero
Reserved
Reserved
Select
PGASoft
PGAZeroCross
Mode
0
0
Changes to affect immediately
0
1
Zero Cross enabled
1
0
Soft Ramp enabled
1
1
Soft Ramp and Zero Cross enabled (default)
Table 14. PGA Soft Cross or Zero Cross Mode Selection
Select
PGA/ADC Input
0
Microphone-Level Input
1
Line-Level Input
Table 15. Analog Input Selection