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參數(shù)資料
| 型號(hào)： | M-8880 |
| 廠商： | Clare, Inc. |
| 英文描述： | M-8880 DTMF Transceiver |
| 中文描述： | 的M - 8880雙音多頻收發(fā)器 |
| 文件頁(yè)數(shù)： | 4/13頁(yè) |
| 文件大小： | 841K |
| 代理商： | M-8880 |
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detected if the CP mode has been selected (see Table 3). Fig-
ure 7 indicates the useful detect bandwidth of the call progress
filter. Frequencies presented to the input (IN+ and IN-) that are
within the “accept” bandwidth limits of the filter are hard-limited
by a high-gain comparator with the IRQ /CP pin serving as the
output. The square wave output obtained from the schmitt trig-
ger can be analyzed by a microprocessor or counter arrange-
ment to determine the nature of the call progress tone being
detected. Frequencies in the “reject” area will not be detected,
andconsequentlytherewillbenoactivityonIRQ/CPasaresult
of these frequencies.
DTMF Generator
TheDTMFtransmitterusedintheM-8880iscapableofgenerat-
ingall16standardDTMFtonepairswithlowdistortionandhigh
accuracy. All frequencies are derived from an external 3.58
MHz crystal. The sinusoidal waveforms for the individual tones
are digitally synthesized using row and column programmable
dividers and switched capacitor digital-to-analog converters.
The row and column tones are mixed and filtered, providing a
DTMF signal with low total harmonic distortion and high accu-
racy. To specify a DTMF signal, data conforming to the encod-
ing format shown in Table 2 must be written to the transmit data
register. Note that this is the same as the receiver output code.
The individual tones that are generated (f
LOW
and f
HIGH
) are re-
ferred to as low-group and high-group tones. Typically, the
high-group to low-group amplitude ratio (twist) is 2 dB to com-
pensate for high-group attenuation on long loops.
Operation:
Duringwriteoperationstothetransmitdataregister,
4-bitdataonthebusislatchedandconvertedtoa2of8codefor
use by the programmable divider circuitry to specify a time seg-
ment length that will ultimately determine the tone frequency.
Thenumberoftimesegmentsisfixedat32,butthefrequencyis
variedbyvaryingthesegmentlength.Whenthedividerreaches
the appropriate count as determined by the input code, a reset
pulse is issued and the counter starts again. The divider output
clocks another counter that addresses the sinewave lookup
ROM. The lookup table contains codes used by the switched
capacitor D/A converter to obtain discrete and highly accurate
DC voltage levels. Two identical circuits are used to produce
row and column tones, which are then mixed using a low-noise
summing amplifier. The oscillator described needs no “startup”
time as in other DTMF generators, since the crystal oscillator is
runningcontinuously,thusprovidingahighdegreeoftoneburst
accuracy. When there is no tone output signal, the TONE pin
assumes a DC level of 2.5 volts (typically). A bandwidth limiting
filter is incorporated to attenuate distortion products above 4
KHz.
BurstMode:
Certaintelephonyapplicationsrequirethatgener-
ated DTMF signals be of a specific duration, determined either
bytheapplicationorbyanyoftheexistingexchangetransmitter
specifications. Standard DTMF signal timing can be accom-
plished by making use of the burst mode. The transmitter is ca-
pable of issuing symmetric bursts/pauses of predetermined
duration. This burst/pause duration is 51 ms
±
1 ms, a standard
interval for autodialer and central office applications. After the
burst/pausehasbeenissued,theappropriatebitissetinthesta-
tusregister,indicatingthatthetransmitterisreadyformoredata.
The timing described is available when the DTMF mode has
been selected. However, when call progress (CP) mode is se-
lected, a secondary burst/pause time is available that extends
this interval to 102 ms
±
2 ms. The extended interval is useful
when precise tone bursts of longer than 51 ms duration and 51
mspausearedesired.NotethatwhenCPmodeandburstmode
have been selected, DTMF tones may be transmitted only and
not received. In applications requiring a nonstandard
burst/pause time, use a software timing loop or external timer.
Thisprovidesthetimingpulseswhentheburstmodeisdisabled
by enabling and disabling the transmitter.
The M-8880 is initialized on powerup sequence with DTMF
mode and burst mode selected.
Single-Tone Generation:
A single-tone mode is available
whereby individual tones from the low group or high group can
begenerated.ThismodecanbeusedforDTMFtestequipment
applications, acknowledgment tone generation, and distortion
measurements. Refer to Table 4 for details.
Distortion Calculations:
The M-8880 is capable of producing
precise tone bursts with minimal error in frequency (see Table
3). The internal summing amplifier is followed by a first-order
low-passswitchedcapacitorfiltertominimizeharmoniccompo-
nents and intermodulation products. The total harmonic distor-
tion for a single tone can be calculated using Equation 1, (see
Figure 9) which is the ratio of the total power of all the extrane-
ous frequencies to the power of the fundamental frequency ex-
pressed as a percentage. The Fourier components of the tone
output correspond to V2f... Vnf as measured on the output
waveform. The total harmonic distortion for a dualtone can be
calculated using Equation 2 (see Figure 9).
Page 4
M-8880
40-406-00012, Rev. G www.clare.com
Figure 7 Call Progress Response
Active
Cell
L1
L2
L3
L4
H1
H2
H3
H4
Output Frequency (Hz)
Specified
697
770
852
941
1209
1336
1447
1633
Actual
699.1
766.2
847.4
948.0
1215.9
1331.7
1471.9
1645.0
% Error
+ 0.30
- 0.49
- 0.54
+ 0.74
+ 0.57
- 0.32
- 0.35
+ 0.73
Table 3 Actual Frequencies vs. Standard
Requirements
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| M-8880-01P | 功能描述:IC TRANSCEIVER DTMF CMOS 20-DIP RoHS:是 類別:集成電路 (IC) >> 接口 - 電信 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS 產(chǎn)品變化通告:Product Discontinuation 06/Feb/2012 標(biāo)準(zhǔn)包裝:750 系列:* |
| M-8880-01SM | 功能描述:IC TRANSCEIVER DTMF CMOS 20-SOIC RoHS:是 類別:集成電路 (IC) >> 接口 - 電信 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS 產(chǎn)品變化通告:Product Discontinuation 06/Feb/2012 標(biāo)準(zhǔn)包裝:750 系列:* |
| M-8880-01T | 功能描述:IC TRANSCEIVER DTMF CMOS 20-SOIC RoHS:是 類別:集成電路 (IC) >> 接口 - 電信 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS 產(chǎn)品變化通告:Product Discontinuation 06/Feb/2012 標(biāo)準(zhǔn)包裝:750 系列:* |
| M-8888 | 制造商:CLARE 制造商全稱:Clare, Inc. 功能描述:DTMF Transceiver |
| M-8888-01 | 制造商:CLARE 制造商全稱:Clare, Inc. 功能描述:DTMF Transceiver |
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