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參數(shù)資料
| 型號： | MT8870 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 5/23頁 |
| 文件大?。?/td> | 177K |
| 代理商： | MT8870 |
Application Note
MSAN-108
A-49
low to high strobing new data into the output latches,
and raising the StD output. As long as an input level
above V
TSt
is maintained StD will remain high
indicating the presence of a valid DTMF signal.
Initially, when no valid tone-pairs are present,
capacitor C is fully charged applying a low voltage to
St/GT. This causes a low at the comparator’s output
and since ESt is also low, Q
2
turns on ensuring that
C is completely charged. In this condition St/GT is in
its output mode (GT function). When a valid tone-
pair is received ESt is raised turning off Q
2
which
puts St/GT in its high impedance input mode and
allows C to discharge through R. If this condition
persists for the tone-present guard time, t
GTP
, the
voltage at St/GT rises above V
TSt
raising StD which
indicates reception of a valid DTMF signal. If the
tone pair drops out before the duration of t
GTP
, ESt is
lowered turning on Q
2
which charges C resetting the
tone-present guard time.
Once a DTMF signal is recognized as valid both ESt
and the comparator output are high. This turns on
Q
1
which discharges C and initializes the tone-
absent guard time, t
GTA
. After the DTMF signal is
removed, ESt is lowered, Q
1
turns off placing St/GT
in its input mode and C begins to charge through R.
Figure 4 - MT8870 Timing Diagram
EXPLANATION OF EVENTS
EXPLANATION OF SYMBOLS
A)
B)
C)
D)
E)
F)
G)
TONE BURSTS DETECTED, TONE DURATION INVALID, OUTPUTS NOT UPDATED.
TONE #n DETECTED, TONE DURATION VALID, TONE DECODED AND LATCHED IN OUTPUTS
END OF TONE #n DETECTED, TONE ABSENT DURATION VALID, OUTPUTS REMIAN LATCHED UNTIL NEXT VALID TONE.
OUTPUTS SWITCHED TO HIGH IMPEDANCE STATE.
TONE #n + 1 DETECTED, TONE DURATION VALID, TONE DECODED AND LATCHED IN OUTPUTS (CURRENTLY HIGH IMPEDANCE).
ACCEPTABLE DROPOUT OF TONE #n + 1, TONE ABSENT DURATION INVALID, OUTPUTS REMAIN LATCHED.
END OF TONE #n + 1 DETECTED, TONE ABSENT DURATION VALID, OUTPUTS REMAIN LATCHED UNTIL NEXT VALID TONE.
V
in
ESt
St/GT
Q
1
-Q
4
StD
DTMF COMPOSITE INPUT SIGNAL.
EARLY STEERING OUTPUT. INDICATES DETECTION OF VALID TONE FREQUENCIES.
STEERING INPUT/GUARD TIME OUTPUT. DRIVES EXTERNAL RC TIMING CIRCUIT.
4-BIT DECODED TONE OUTPUT.
DELAYED STEERING OUTPUT. INDICATES THAT VALID FREQUENCIES HAVE BEEN PRESENT/ABSENT FOR THE REQUIRED GUARD TIME THUS
CONSTITUTING A VALID SIGNAL.
TONE OUTPUT ENABLE (INPUT). A LOW LEVEL SHIFTS Q
1
-Q
4
TO ITS HIGH IMPEDANCE STATE.
MAXIMUM DTMF SIGNAL DURATION NOT DETECED AS VALID
MINIMUM DTMF SIGNAL DURATION REQUIRED FOR VALID RECOGNITION
MAXIMUM TIME BETWEEN VALID DTMF SIGNALS.
MAXIMUM ALLOWABLE DROP OUT DURING VALID DTMF SIGNAL.
TIME TO DETECT THE PRESENCE OF VALID DTMF SIGNALS.
TIME TO DETECT THE ABSENCE OF VALID DTMF SIGNALS.
GUARD TIME, TONE PRESENT.
GUARD TIME, TONE ABSENT.
TOE
t
REC
t
REC
t
ID
t
DO
t
DP
t
DA
t
GTP
t
GTA
V
in
ESt
St/GT
Q
1
-Q
4
StD
TOE
EVENTS
A
B
C
D
E
F
G
t
REC
t
REC
t
ID
t
DO
TONE #n
TONE
#n + 1
TONE
#n + 1
t
DP
t
DA
t
GTP
t
GTA
t
PQ
t
QStD
t
PSrD
t
PTD
t
PTE
# n
# (n + 1)
HIGH IMPEDANCE
DECODED TONE # (n-1)
V
TSt
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MT8880C | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE-1 | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CC | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CN | ISO2-CMOS Integrated DTMFTransceiver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MT8870BE | 制造商:Panasonic Industrial Company 功能描述:RECEIVER |
| MT8870D | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC-1 | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DE | 制造商:Microsemi Corporation 功能描述: |
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