© 1999 Consumer Microcircuits Limited

9

D/663/3

1.5.4

Decode Output Truth Table

D3

D2

D1

D0

Conditions

0

0

0

0

No Signal

0

0

0

1

Call Progress Dual Tones:

Will detect 350+440, 400+450, 440+480 Hz tones

0

0

1

0

Non Call Progress Signal, e.g. Voice Activity

0

0

1

1

Call Progress Dual Tone including 620Hz Detection:

Will detect 480+620 Hz tones

0

1

0

0

Special Information Tone:

Will detect 950, 1400 and 1800 Hz tones

0

1

0

1

Call Progress Single Tone:

Will detect 400, 425, 440 and 450 Hz tones

0

1

1

0

Will detect a single tone lying outside the Call Progress

Band and within the Non Call Progress signal range

0

1

1

1

Call Progress Single Tone including 620Hz Detection:

Will detect 600 and 620 Hz tones

1

0

0

0

Fax/modem High Tone:

Will detect 2100 and 2200 Hz tones

1

0

0

1

Reserved for future use

1

0

1

0

Reserved for future use

1

0

1

1

Reserved for future use

1

1

0

0

Fax/modem Low Tone:

Will detect 1200 and 1300 Hz tones

1

1

0

1

Reserved for future use

1

1

1

0

Reserved for future use

1

1

1

1

Reserved for future use

1.6

Application Notes

1.6.1

General

Apply a reset after power-up by taking the ENABLE pin low. This places the device in a powersave mode and

resets the internal circuits. It also places the data word output (D0-D3) in a high impedance state, regardless

of the level on the CSN pin.

From this mode the device can be returned to normal operation without any additional settling time, when

using the component values recommended in Figure 2. The tone response times remain the same and are

given in section 1.7.1.

An interrupt is produced when the decode state is changed. This interrupt is reset by CSN going to logic "0".

When CSN is permanently at "0", the interrupt condition is a 5 µs logic "0" pulse on the IRQN pin. When CSN

is set to logic "1", the data word output (D0-D3) goes into a high impedance state.