NSAM265SR Datasheet, PDF (9/58 Pages) National Semiconductor (TI) – CompactSPEECH Digital Speech Processors

1 0 Theory of Operation (Continued)
Other Detectors
Detection of busy and dial tones and no-energy is con-
trolled by tunable parameters You should tune the thresh-
olds of these parameters to fit your hardware For more
information see the TUNE command in Section 3 2
Dial and busy tone detectors work with a band pass filter
that limits the frequency range in which tones can be detect-
ed to 0 Hz–1100 Hz Its frequency response is illustrated in
Figure 1-1 and the busy tone cadences in Figure 1-2
Tone Generation
The CompactSPEECH can generate DTMF tones and sin-
gle-frequency tones from 300 Hz to 2000 Hz in increments
of 100 Hz CompactSPEECH tone generation conforms with
EIA-470-RS standard Note however that you may have to
change the value of some tunable parameters in order to
meet the standard specifications since the energy level of
generated tones depends on the analogue circuits being
used
 Tune the DTMF TWIST LEVEL parameter to control
the twist level of the generated DTMF tones
 Use the VC command and tune the TONE GENERA-
TION LEVEL parameter to control the energy level at
which these tones are generated
 Use the GT command to specify the DTMF tones and the
frequency at which single tones are generated
1 9 SPEECH SYNTHESIS
Speech synthesis enables you to announce prerecorded
voice prompts or form a sentence by combining individual
words A built-in is supplied with the CompactSPEECH for
announcing the number of messages and the time and day
The main speech synthesis features are
 On-chip English vocabulary for announcing the number
of messages and the time and day
 Additional vocabularies on ROM or FLASH
(NSAM265SF only)
 International Vocabulary Support (IVS) without changing
the microcontroller code
 Up to 220 words in each vocabulary Each word can be
announced separately
 Sentences announced from a predefined table of sen-
tences
 On-the-fly sentence announcement
1 9 1 Explanation of Terms
The following terms are used throughout this document
Vocabulary
A complete set of words and sen-
tences Words are arranged in a word
table Sentences are arranged in a
sentence table
Word Table
A set of words arranged in a table
as part of a vocabulary
Sentence Table
A set of sentences arranged in a ta-
ble as part of a vocabulary The
structure of a sentence table is de-
scribed in detail in the International
Vocabulary Support User’s Manual
The Internal Vocabulary includes a
built-in table with two entries
Word
An entry in a word table which repre-
sents a spoken word or phrase A
word is played with the SW (Say
Words) or SO (Say One word) com-
mands
Sentence
A series of words synthesized from a
vocabulary A sentence is defined as
an entry in the sentence table and is
synthesized with the SS (Say Sen-
tence) or SAS (Say Argumented Sen-
tence) command or is synthesized
‘‘on-the-fly’’ with the SW command
Internal Vocabulary
The vocabulary in English which re-
sides on the CompactSPEECH’s in-
ternal ROM
External Vocabulary An optional vocabulary which resides
on external ROM or (NSAM265SF
only) FLASH
International
Vocabulary
Support (IVS)
A method that enables the same
CompactSPEECH command to syn-
thesize sentences with the same
meaning but in different languages
from separate external vocabularies
FIGURE 1-1 Busy and Dial Tone Band Pass Filter Frequency Response
TL EE 12378 – 3
TL EE 12378 – 47
E₁ b E₃ k 90 ms
S₁ b S₃ k 90 ms 100 k E_i k 1700 ms 50 k S_i k 1300 ms
FIGURE 1-2 Busy Tone Detector Cadence Specification
9