The tone mode start-up sequence is as follows:
- After detecting VMIC > 2.35V, the switch connecting the MIC and REM pins together (Switch B) is opened after time tOFFB.
- After a delay of tONA after VMIC > 2.35V, the VSHUNT and MICPWR pins are shorted (with Switch A). The microphone is enabled by turning on the FET switch that is controlled by the MICPWR pin.
- After a delay to allow the switches to settle, tM2T after VMIC > 2.35V, the CD326x sends a preset acknowledge (ACK) tone sequence.
- The specially enabled audio interface detects the ACK sequence and authenticates the presence of the CD326x.