SI3230PPQX-EVB Silicon Laboratories Inc, SI3230PPQX-EVB Datasheet - Page 34

• Manufacturer Part Number: SI3230PPQX-EVB
• Description: BOARD EVAL W/DISCRETE INTERFACE
• Manufacturer: Silicon Laboratories Inc
• Series: ProSLIC®r

Specifications of SI3230PPQX-EVB

• Main Purpose: Interface, Analog Front End (AFE)
• Utilized Ic / Part: Si3230
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Si3230
The pulse metering oscillator has a volume envelope
(linear ramp) on the on/off transitions of the oscillator.
The volume value is incremented by the value in the
PLSD register (indirect Register 23) at an 8 kHz rate.
The sinusoidal generator output is multiplied by this
volume before being sent to the DAC. The volume will
ramp from 0 to 7FFF in increments of PLSD so the
value of PLSD will set the slope of the ramp. When the
pulse metering signal is turned off, the volume will ramp
to 0 by decrementing according to the value of PLSD.
34
Figure 15. Pulse Metering Volume Envelope
Pulse Metering Oscillator
8 Khz
Volum e
Clip to 7FFF or 0
+/–
X
To DAC
PLSD
Preliminary Rev. 0.96
2.6. DTMF Detection
The dual-tone multi-frequency (DTMF) tone signaling
standard is also known as touch tone. It is an in-band
signaling system used to replace the pulse-dial
signaling standard. In DTMF, two tones are used to
generate a DTMF digit. One tone is chosen from four
possible row tones, and one tone is chosen from four
possible column tones. The sum of these tones
constitutes one of 16 possible DTMF digits.
2.6.1. DTMF Detection Architecture
DTMF detection is performed using a modified Goertzel
algorithm to compute the dual frequency tone (DFT) for
each of the eight DTMF frequencies as well as their
second harmonics. At the end of the DFT computation,
the squared magnitudes of the DFT results for the eight
DTMF fundamental tones are computed. The row
results are sorted to determine the strongest row
frequency; the column frequencies are sorted as well.
At the completion of this process, a number of checks
are made to determine whether the strongest row and
column tones constitute a DTMF digit.
The detection process is performed twice within the
45 ms minimum tone time. A digit must be detected on
two consecutive tests following a pause to be
recognized as a new digit. If all tests pass, an interrupt
is generated, and the DTMF digit value is loaded into
the DTMF register. If tones are occurring at the
maximum rate of 100 ms per digit, the interrupt must be
serviced within 85 ms so that the current digit is not
overwritten by a new one. There is no buffering of the
digit information.