STA326
are normally used to set the maximum allowable digital gain and to hard-set gain differences between cer-
tain channels. These values are normally set at the initialization of the IC and not changed. The individual
channel volumes are adjustable in 0.5dB steps from +48dB to -80 dB. The master volume control is nor-
mally mapped to the master volume of the system. The values of these two settings are summed to find
the actual gain/volume value for any given channel.
When set to 1, the Master Mute will mute all channels, whereas the individual channel mutes (CxM) will
mute only that channel. Both the Master Mute and the Channel Mutes provide a “soft mute” with the vol-
ume ramping down to mute in 4096 samples from the maximum volume setting at the internal processing
rate (~96kHz). A “hard mute” can be obtained by commanding a value of all 1’s (FFh) to any channel vol-
ume register or the master volume register. When volume offsets are provided via the master volume reg-
ister any channel whose total volume is less than –100dB will be muted.
All changes in volume take place at zero-crossings when ZCE = 1 (configuration register E) on a per chan-
nel basis as this creates the smoothest possible volume transitions. When ZCE=0, volume updates will
occur immediately.
The STA326 also features a soft-volume update function that will ramp the volume between intermediate
values when the value is updated, when SVE = 1 (configuration register E). This feature can be disabled
by setting SVE = 0.
Each channel also contains an individual channel volume bypass. If a particular channel has volume by-
passed via the CxVBP = 1 register then only the channel volume setting for that particular channel affects
the volume setting, the master volume setting will not affect that channel. Also, master soft-mute will not
affect the channel if CxVBP = 1.
Each channel also contains a channel mute. If CxM = 1 a soft mute is performed on that channel
Table 16. Master Volume Offset as a function of MV (7..0).
MV (7..0)
00000000 (00h)
00000001 (01h)
00000010 (02h)
…
Volume Offset from Channel Value
0dB
-0.5dB
-1dB
…
-38dB
01001100 (4Ch)
…
…
11111110 (FEh)
11111111 (FFh)
-127dB
Hard Master Mute
Table 17. Channel Volume as a function of CxV (7..0)
CxV (7..0)
00000000 (00h)
00000001 (01h)
00000010 (02h)
…
Volume
+48dB
+47.5dB
+47dB
…
01100001 (5Fh)
01100000 (60h)
01011111 (61h)
…
+0.5dB
0dB
-0.5dB
…
11111110 (FEh)
11111111 (FFh)
-79.5 dB
Hard Channel Mute
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STMICROELECTRONICS [ ST ]
