參數(shù)資料
型號(hào)： NSAM265SRA
廠商： National Semiconductor Corporation
英文描述： CompactSPEECH Digital Speech Processors
中文描述： CompactSPEECH數(shù)字語(yǔ)音處理器
文件頁(yè)數(shù)： 8/58頁(yè)
文件大小： 712K
代理商： NSAM265SRA
1.0 Theory of Operation
(Continued)
1.7.3. Memory Operating Modes in NSAM265SF
The NSAM265SF supports two operating modes of the
FLASH memory manager (selected by the CFG command):
Normal Mode
In this mode, the NSAM265SF always keeps one free block
for memory management. The EVDMEMFULL event is set
when all but one good AFLASH blocks are full, and record-
ing on the last available free block is not allowed.
Maximum recording time in this mode:
On one 8-Mbit FLASH (no bad blocks) device: 28 minutes
and 8 seconds.
On one 4-Mbit FLASH (no bad blocks) device: 13 minutes
and 8 seconds.
Memory Intensive Mode
All good blocks are available for message recording. As
long as there is one free block available for memory man-
agement, this mode is the same as normal mode. The Com-
pactSPEECH sets the EVDMEMLOW event when approxi-
mately 20 seconds recording time remain on the one-be-
fore-last FLASH block. The EVDMEMFULL event is set
only when all the blocks are full.
However, if the last good block is used for recording, the
NSAM265SF no longer has a free block for memory man-
agement, and therefore may fail to free memory space i.e.,
execute the FR command. The microcontroller must delete
all messages, with the MESSAGEDSAFE bit cleared, to
guarantee that at least one block is erased, and can be
used for memory management.
When there is no block available for memory management,
and you attempt to record a message with the MESSAGED
SAFE
bit set, the CompactSPEECH sets the EVD
MEMFULL event and does not allow you to record. Thus it
is possible to avoid a situation where a safe message must
be deleted to free a FLASH block.
Maximum recording time in this mode:
On one 8 Mbits FLASH (no bad blocks) device: 30 minutes.
On one 4 Mbits FLASH (no bad blocks) device: 15 minutes.
1.8 TONE AND NO-ENERGY DETECTION
The CompactSPEECH detects DTMF, busy and dial tones,
and no energy (VOX). This enables remote control opera-
tions and call progress. Detection is active throughout the
operation of the CompactSPEECH. Detection can be con-
figured using the SDET (Set Detectors Mask) command,
which controls the reporting of occurrence of tones, and the
RDET (Reset Detectors) command which resets the detec-
tors.
DTMF
DTMF detection may be reported at starting point, ending
point, or both. The report is made through the status word
(for further details, see GSW command in Section 3.2).
The DTMF detector specifications as measured on the line
input using the NSV-AM265-DAA board are summarized be-
low (see Table 1-2).
Echo Cancellation
Echo cancellation is a technique used to improve the per-
formance of DTMF tone detection during speech synthesis,
tone generation and OGM playback. For echo cancellation
to work properly, AGC must not be active in parallel. Thus,
to take advantage of echo cancellation, the microcontroller
must control the AGC, i.e., disable the AGC during PLAY,
SYNTHESIS and TONEDGENERATE states and enable it
again afterwards. If AGC can not be disabled, do not use
echo cancellation. The microcontroller should use the CFG
command to activate/deactivate echo cancellation. (For fur-
ther details, see Section 3.2.)
Echo cancellation applies only to DTMF tones. Busy and
dial tones detection is not affected by this technique.
TABLE 1-2. DTMF Detector Specifications
Play
Record/
Idle
Detection Sensitivity
(Note A)
b
33 with Echo Canceller
b
23 w/o Echo Canceller
b
40 dBm
Accepted
DTMF Length
l
50 ms
l
40 ms
Frequency Tolerance
g
1.5%
g
1.5%
S/N Ratio
12 dB
12 dB
Minimum Spacing
(Note B)
l
45 ms
l
45 ms
Normal Twist
8 dB
8 dB
Reverse Twist
(Note C)
4 dB or 8 dB
4 dB or 8 dB
Note A:
Performance depends on DAA design.
Note B:
If the interval between two consecutive DTMF tones is less than or
equal to 20 ms, the two are detected as one long DTMF tone. If the interval
between two consecutive DTMF tones is between 20 ms and 45 ms, sepa-
rate detection is unpredictable.
Note C:
Determined according to the DTMFDREVDTWIST tunable param-
eter value.
8
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