In I2S mode, the ASDATAx pins are outputs and the DSDATAx pins are inputs. Any unused ASDATA pins should be left unconnected. Any unused DSDATA pins should be connected to ground.
In TDM single- or dual-line modes, standalone or daisy-chain modes, the function of the pins will change as follows:
ASDATA1: TDM ADC data output, leave unconnected
ASDATA2: TDM ADC data input, connect to ground
DSDATA1: TDM DAC data input, connect to ground
DSDATA2: TDM DAC data output, leave unconnected
DSDATA3: TDM DAC2 data input (dual-line), connect to ground
DSDATA4: TDM DAC2 data output, leave unconnected
In TDM/AUX mode, the function of the pins will change as follows:
ASDATA2: AUX DAC1 data output, leave unconnected
DSDATA2: AUX ADC1 data input, connect to ground
DSDATA3: AUX ADC2 data input, connect to ground
DSDATA4: AUX DAC2 data output, leave unconnected
Please see the datasheet of the specific device for more details.
You certainly can mute the unused DACs. It will not hurt. If the DSDATA pins are grounded for those channels then the DACs will be receiving all zeros so muting I suppose is simply an extra precaution. However, I would still ground the unused pins.
In addition: does it suffice to mute the unused DACs in the register
“DAC Individual Channel Mutes Register (Address 5, 0x05)” or are other register settings also required?