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STW5093

Earpiece amplifier gain selection:

Earpiece Receive gain can be programmed in 2 dB step from 0 dB to -30 dB relative to the maximum with bits

4 to 7.

0 dBmO voltage at the output of the amplifier on pin VFr is 0.9825 Vrms when 0dB gain is selected down to

30.925 Vrms when -30dB gain is selected.

Extra amplifier gain selection:

Extra Receive amplifier gain can be programmed in 2 dB step from 0 dB to -30 dB relative to the maximum with

bits 0 to 3.

to 61.85 mVrms when -30 dB gain is selected.

CONTROL REGISTER CR7:

First byte of a READ or a WRITE instruction to Control Register CR7 is as shown in TABLE 1. Second byte is

as shown in TABLE 9.

Tone/Ring amplifier gain selection

Output level of Ring/Tone generator, before attenuation by programmable attenuator is 1.6 Vpk-pk when f1 gen-

erator is selected alone or summed with the f2 generator and 1.26 Vpk-pk when f2 generator is selected alone.

Selected output level can be attenuated down to -27 dB by programmable attenutator by setting bits 4 to 7.

Frequency mode selection

Bits 'F1' (3) and 'F2' (2) permit selection of f1 and/or f2 frequency generator according to TABLE 9.

When f1 (or f2) is selected, output of the Ring/Tone is a squarewave (or a sinewave) signal at the frequency

selected in the CR8 (or CR9) Register.

When f1 and f2 are selected in summed mode, output of the Ring/Tone generator is a signal where f1 and f2

frequency are summed.

In order to meet DTMF specifications, f2 output level is attenuated by 2dB relative to the f1 output level.

Frequency temporization must be controlled by the microcontroller.

Waveform selection

Bit 'SN' (1) selects waveform of the output of the Ring/Tone generator. Sinewave or squarewave signal can be

selected.

DTMF selection

Bit DE (0) permits connection of Ring/Tone/DTMF generator on the Transmit Data path instead of the Transmit

Amplifier output. Earpiece or extra receive output feed-back may be provided by sidetone circuitry by setting bit

SI or directly by setting bit RTE in Register CR4. Loudspeaker feed-back may be provided directly by setting bit

RTL in Register CR4.

CONTROL REGISTERS CR8 AND CR9

First byte of a READ or a WRITE instruction to Control Register CR8 or CR9 is as shown in TABLE 1. Second

byte is respectively as shown in TABLE 10 and 11.

If "standard frequency tone range" is selected, Tone or Ring signal frequency value is defined by the formula:

f1 = CR8 / 0.128 Hz