ISD-T360SB Datasheet, PDF (52/109 Pages) List of Unclassifed Manufacturers – VoiceDSP Digital Speech Processor with Master/Slave, Full-Duplex Speakerphone, Multiple Flash and ARAM/DRAM Support

ISD-T360SB
2—SOFTWARE
DTMF SW AGC
In order to remove the linkage between the HW
AGC and the detection level of the DTMF detec-
tor, two new tunable parameters are added.
These tunable parameters define the gain of the
SW AGC for DTMF signals.
DTMF_DET_AGC_IDLE - SW AGC for DTMF detec-
tion in Idle and Record states. When increment-
ing this tunable by 1, the dynamic range is
increased by 3 dB.
DTMF_DET_AGC_PLAY - SW AGC for DTMF detec-
tion in Play and Tone_Generate states. When in-
crementing this tunable by 1, the dynamic range
is increased by 3 dB.
ECHO CANCELLATION
Echo cancellation is a technique used to im-
prove the performance of DTMF detection dur-
ing speech synthesis, tone generation, and
OGM playback. For echo cancellation to work
properly, HW AGC must not be active in parallel.
Thus, to take advantage of echo cancellation,
the microcontroller must control the HW AGC, if
exists, (i.e., disable the HW AGC during PLAY,
SYNTHESIS and TONE_GENERATE states and en-
able it again afterwards). If HW AGC can not be
disabled, do not use echo cancellation.
The microcontroller should use the CFG com-
mand to activate/deactivate echo cancella-
tion.
2.3.3 TONE AND ENERGY DETECTION (CALL
PROGRESS)
The VoiceDSP processor detects busy and dial
tones, constant energy level, and no-energy
(VOX). This enables call progress tracking. De-
tection is active throughout the operation of the
VoiceDSP processor. Detection can be config-
ured using the SDET (Set Detectors Mask) com-
mand, which controls the reporting of the
occurrence of tones, and the RDET (Reset De-
tectors) command which resets the detectors.
The accuracy of the tone length, as reported by
the tone detectors, is ±10 ms.
TUNABLE PARAMETERS
Tunable parameters control the detection of
busy and dial tones, constant energy level (in
the frequency range 200–3400Hz), and no-ener-
gy. These parameters should be tuned to fit the
system hardware. In addition, changes may be
required to the tunable parameters according
to the setting (On or Off) of the HW Automatic
Gain Control (HW AGC), if exists. For more infor-
mation refer to tables 2-7, 2-8 of the Command
Description section.
NOTE
Normally, a HW AGC is not required with
The ISD-T360SB, since SW AGC is active for
the VCD algorithm, DTMF detection and
the speakerphone module.
2-12
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