ST5080 datasheet(20/32 Pages) STMICROELECTRONICS

20 / 32 page

Current limitation is approximatively 150 mApk.

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 at-

tenuation by programmable attenuator is 2.4 Vpk-

pk when f1 generator is selected alone or

summed with the f2 generator and 1.9 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 TA-

BLE 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)

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 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 di-

rectly 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 TA-

BLE 1. Second byte is respectively as shown in

TABLE 10 and 11.

Tone or Ring signal frequency value is defined by

the formula:

f1 = CR8 / 0.128 Hz

and

f2 = CR9 / 0.128 Hz

where CR8 and CR9 are decimal equivalents of

the binary values of the CR8 and CR9 registers

respectively. Thus, any frequency between 7.8 Hz

and 1992 Hz may be selected in 7.8 Hz step.

TABLE 12 gives examples for the main frequen-

cies usual for Tone or Ring generation.

ST5080A

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