STA328

22/41

7.8.2.2Channel 2 Volume (Address 09h)

7.8.2.3Channel 3 Volume (Address 0Ah)

7.8.3

Volume Description

The volume structure of the STA328 consists of individual volume registers for each of the three channels

and a master volume register, and individual channel volume trim registers. The channel volume settings

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 STA328 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).

D7

D6

D5

D4

D3

D2

D1

D0

C2V7

C2V6

C2V5

C2V4

C2V3

C2V2

C2V1

C2V0

011000

00

D7

D6

D5

D4

D3

D2

D1

D0

C3V7

C3V6

C3V5

C3V4

C3V3

C3V2

C3V1

C3V0

011000

00

MV (7..0)

Volume Offset from Channel Value

00000000 (00h)

0dB

00000001 (01h)

-0.5dB

00000010 (02h)

-1dB

……

01001100 (4Ch)

-38dB

……

11111110 (FEh)

-127dB

11111111 (FFh)

Hard Master Mute