NSAM265SR Datasheet, PDF (31/58 Pages) National Semiconductor (TI) – CompactSPEECH Digital Speech Processors

3 0 Command Set (Continued)
TABLE 3-1 Tunable Parameters (Continued)
Index Parameter Name
Description
Default
24 ECHO DELAY
The near echo delay in samples For example the default value is computed as
4
follows The near echo delay is assumed 500 ms Since the sampling rate is 8000 Hz
(i e 125 ms per sample) the value of ECHO DELAY is 4
Legal values 0 to 255
25 Reserved
26 DTMF REV TWIST Controls the reverse twist level at which CompactSPEECH detects DTMF tones While
0
the normal twist is set at 8 dB the reverse twist can be either 8 dB (default) or 4 dB (If
this parameter is set to 1)
27 DTMF TWIST LEVEL A one byte value that controls the twist level of a DTMF tone generated by the GT
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command by controlling the energy level of each of the two tones (low frequency and
high frequency) composing the DTMF tone The Least Significant Nibble (LSN)
controls the low tone and the Most Significant Nibble (MSN) controls the high tone
The energy level of each tone as measured on the output of a TP3054 codec (before
the DAA) connected to the CompactSPEECH is summarized in the following table
Nibble Value
Tone energy (dB-Volts)
0
0
1
b17 8
2
b14 3
3
b12 9
4
b12 4
5
b12 0
6
b11 9
7
b11 85
8 – 15
b11 85
The volume of the generated tone during meaurements was 6
(TONE GENERATION LEVELaVOL LEVEL e 6)
The default level means that the high tone is at b14 3 dBv and the low tone at
b12 4 dBv which gives DTMF twist level of 1 9 dB
VC
Volume Control vol level
NSAM265SR
NSAM265SF
Controls the energy level of all the output generators (play-
back tone generation and voice synthesis) with one com-
mand The resolution is 3 dB
The actual output level is composed of the tunable level
variable plus the vol level The valid range for the actual
output level of each output generator is defined in Table 3-1
For example if the tunable variable VCD LEVEL is 6 and
vol level is b2 then the output level equals VCD LEVEL
a vol level e 4
WRAM
Write RAM tag data
NSAM265SR
NSAM265SF
This command creates a new message with a message tag
tag The following 32 bytes of data are stored as the new
message data in the message memory
The WRAM command switches the CompactSPEECH to
the MEMORY WRITE state As long as it remains in this
state each subsequent WRAM command appends new
message data to the end of the previous data The Com-
pactSPEECH remains in the MEMORY WRITE state until
an S command is issued Note that while the Compact-
SPEECH is in MEMORY WRITE state the tag parameter is
ignored
If the memory becomes full recording stops and EV MEM-
FULL is set in the status word
EV MEMFULL will be also set in the NSAM265SF if there
is only one AFLASH block available for recording and the
MESSAGE SAFE bit in the tag parameter is set
NSAM265SR
If an attempt to record more than the maximum number of
messages is made an ERR INVALID error is reported
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