1ms

calibration

frequency

2ms

button or ACK

selected frequency

4ms

continue ACK selected frequency

(power-up only)

1.67ms

tCAL

tCAL

2.89ms

TONE pin

Tone pulses

De-bounced

button press

or power-up

Tone pulse

counter

(A.)

(B.)

(C.)

(D.)

Figure 7-6. Tone Transmit and Decode Method

A.

Count 63 tone pulses to set tCAL.

B.

Count n tone pulses over tCAL.

C.

Tone frequency decoded from n value.

D.

Tone activity sampled. If active, ACK tone received. If not active, button tone received.

The CD326x remains in tone mode until the MIC pin voltage falls below 0.8V. When power recovers, the

CD326x enters button mode or tone mode depending on the voltage detected at the MIC pin. See Section 7.3.4

for more details about this process.

0V

2.5V

tCAL

tACK

Time

Calibration tone tCAL = 0.9ms (typ)

ACK tone tACK = 5.5ms

(typ)

Figure 7-7. Tone Mode Acknowledge Timing

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CD3268A, CD3269A

SCHS463 – MAY 2025

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