AM79C30AVC datasheet(27/101 Pages) AMD

27 / 101 page

Am79C30A/32A Data Sheet

The output frequency of the DTMF tone generator ap-

proximately equals:

where

i is the decimal equivalent of value programmed

into the FTGR register. This allows the DTMF genera-

tor to supply common dual tone call progress signals

such as Busy or Dial tones.

Note:

These coefficients do not apply to the DTMF generator.

The ATGR registers allow the user to program a gain of

–18 dB to 0 dB in 2-dB steps. Example ATGR codes to

obtain amplitude gains are listed in Table 23. 0 dB im-

plies a level of +3 dBm0. The gain values are rounded

off to the nearest 1 dB.

Note:

See the amendment to Table 23 following page 100.

Secondary Tone Ringer

A Secondary Tone Ringer is included, which is able to

ring the phone using the LS outputs while a voice con-

versation is in progress on the EAR outputs. The STR

is louder than the Tone Generator, and may be used

with or without enabling the MAP in order to provide

flexible control of system power consumption. The STR

is not available if the INIT register is programmed to

Idle or Power-Down mode. The amplitude and fre-

quency of the STR square-wave output waveform is

programmable via the STRA and STRF registers, re-

spectively. If both the LS outputs from the MAP receive

path and the STR are simultaneously enabled, priority

is given to the STR connection. The STR is available for

both the DSC and IDC circuits. A legal value must be

programmed in the STRF register before the STR is

enabled.

Table 22.

Tone Ringer and Tone Generator

Frequency Coefficients

Frequency (Hz)

Hex Code

2666

2000

1600

1333

1142

1000

889

800

727

667

615

571

533

500

471

444

421

400

381

364

348

333

320

DTMF Frequency in Hz

64000

integer 8192

⁄

() 1

----------------------------------------------------

Table 23.

Amplitude Gain Coefficients

Gain (dB)

Hex Code

–18

–16

–14

–12

–10

–8

–6

–4

–2

010

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