st5080d STMicroelectronics, st5080d Datasheet - Page 20

• Manufacturer Part Number: st5080d
• Description: Piafe Programmable Isdn Audio Front End
• Manufacturer: STMicroelectronics

ST5080A
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 generatoris 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)
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
20/32
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:
and
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.
f1 = CR8 / 0.128 Hz
f2 = CR9 / 0.128 Hz