Cirrus Logic CS4351 - Manual (Page 28)

28 DS566F1
CS4351
6.5.1 Digital Volume Control (VOL7:0) Bits 7-0
Default = 00h (0 dB)
Function:
The Digital Volume Control registers allow independent control of the signal levels in 1/2 dB increments
from 0 to -127.5 dB. Volume settings are decoded as shown in
Table 9 . The volume changes are imple-
mented as dictated by the Soft and Zero Cross bits in the Power and Muting Control register.
The actual attenuation is determined by taking the decimal value of the volume register and multiplying
by 6.02/12.
6.6 Ramp and Filter Control - Register 07h
6.6.1 Soft Ramp and Zero Cross Control (SZC1:0) Bits 7-6
Default = 10
Function:
Immediate Change
When Immediate Change is selected all level changes will take effect immediately in one step.
Zero Cross
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.
Soft Ramp PCM
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.
Binary Code Decimal Value Volume Setting
00000000 0 0 dB
00000001 1 -0.5 dB
00000110 6 -3.0 dB
11111111 255 -127.5 dB
Table 9. Example Digital Volume Settings
7 6 5 4 3 2 1 0
SZC1 SZC0 RMP_UP RMP_DN Reserved FILT_SEL Reserved Reserved
1 0 1 1 0 0 0 1
SZC1 SZC0 Description
0 0 Immediate Change
0 1 Zero Cross
1 0 Soft Ramp
1 1 Soft Ramp on Zero Crossings