MX613DW Ver la hoja de datos (PDF) - CML Microsystems Plc
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MX613DW Datasheet PDF : 10 Pages
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Global Call Progress Tone Detector
4
MX613 Preliminary Information
Application Information ......
Principles of Decoder Operation
Level Detection
Because level and frequency discrimination operations take place in parallel, the audio signal should, under normal
circumstances, be input to both Signal In and Level In pins via coupling capacitors.
If the input signal level (Level In) is outside the preset ‘Must/Must Not Decode’ thresholds (see Specifications), the
Universal Call Progress Decoder will be disabled.
If it is wished to disregard signal inputlevels at the Level In pin and attempt to decode under all conditions, the decoder
may be permanently enabled by holding the Level In pin at V .
DD
The MX613 can disabled by pulling Level In to V .
SS
NOTONE Recognition
The NOTONE condition can be recognized using µProcessor software timing as below.
a. Set the µP timer period to a period greater than the relevant frequency-band measurement period (13.16ms
or 39.47ms).
b. Each ‘Tone Measurement Complete’ interrupt from the MX613 must reset the µP timer.
c. With NOTONE or white noise at the decoder input, the MX613 on-chip timer will be continually reset.
i. ‘Tone Measurement Complete' interrupt will not occur - the µP timer will run.
ii. The µP Timer time-out can be considered as a NOTONE indication.
Level In
In Limits
Out of Limits
VDD
VSS
Timer
Running
Reset
Running/Reset
Reset
IRQ
Enabled
Disabled
Enabled/Disabled
Disabled
Data Out
Enabled
Disabled
Enabled
Disabled
(frozen to previous bit-5 level
(dependent upon Quality measurement)
(frozen to previous bit-5 level)
Frequency Band Discrimination
The input signal is amplified by a self-biased (zero-crossing) inverting amplifier and then ‘filtered’ to remove high-
frequency noise and jitter.
High (HI) and Low (LO) counters are employed to determine the input frequency band (HI = 900Hz to 2150Hz,
LO = 300Hz to 660Hz).
If the input frequency is in the LO Band, the device will operate as a LO Band decoder and will remain so until a
HI frequency signal is detected. If the input frequency is in the HI Band, the device will operate as a HI Band
decoder and will remain so until a LO frequency signal is detected.
Frequency band monitoring is continuous with the band selection taking place every 9.8ms. It will therefore take
9.8ms from Power-Up to set up the initial correct decode frequency band.
On-Chip Timer Operation
For frequency measurement, the MX613 counts the number of input cycles in a fixed time period. This fixed
period, measured by the continuous on-chip timer, is set to 13.16ms for HI Band inputs and 39.47ms for LO Band
inputs.
When the timer expires the following actions take place:
a. A HI or LO (“1” or “0”) band indication bit is latched into Bit-5 of the Serial Output Port.
b. The Frequency Counter count of 5-bits is latched into the Serial Output Port (Bit-4 [MSB] to Bit-0). The
Serial Output Port Contains 6-bits, if 8 Serial Clock edges are employed, two extra “0s”, which should be
ignored, will be output last.
c. An interrupt is generated (IRQ) to the µProcessor. The contents of the Serial Output Port should be read
before the next interrupt is expected; if not data will be overwritten.
When the Chip Select input is set to “0” the interrupt is reset.
The On-Chip Timer and Frequency Counter will be reset in mid-count, and therefore unable to allow a valid
measurement, under the following conditions:
a. A change of decode frequency band.
b. Decoder disabled; signal input level out of specification or Level Detect input set to VSS.
c. Signal Quality Assessment considered ‘Bad’.
d. Input signal frequency outside limits.
© 1997 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 910 744-5050 Fax: 910 744-5054
Doc. # 20480086.003
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USAAll trademarks and service marks are held by their respective companies
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