CMX838 Просмотр технического описания (PDF) - MX-COM Inc
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CMX838 Datasheet PDF : 70 Pages
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FRS/PMR446/GMRS Family Radio Processor
18
CMX838 Advance Information
4.2 Tone Signaling Processor
4.2.1 Tone encoding/decoding
The tone signaling processor includes CTCSS encode and decode functions as well as an audio frequency
ringing/alert tone generator. The signaling processor is comprised of a configurable analog filter controlled by
the SUBAUDIO ANALOG CONTROL Register ($97) and a digital processor controlled by configuration tasks.
All device configuration data is passed over the device’s C-BUS serial interface. The configuration tasks to
setup the digital processor are simply C-BUS transaction sequences, which download task argument data
followed by a task request command. In typical applications, once the tone signaling processor is initialized,
its primary behavior (CTCSS encode and decode) is steered by the TX/RX bit of the SETUP Register ($80).
The subaudio filter is shared between transmit and receive. It is used to remove the speech signal from the
receive subaudio signal, leaving only the subaudible squelch signal as input to the digital processor. This filter
is also used to smooth the digitally generated subaudible signals in the transmit mode. Following the filter is a
gain trimmer stage that can adjust the signal level ±7.5dB in 0.5dB steps into the decoding section or out to
the modulation section. Approximately 20dB of gain is provided in the receive path and 20dB of attenuation in
the transmit path.
Subaudio
LPF1
Gain
2 or 22db
Subaudio
LPF2
Gain
0 or -18dB
Subaudio
RX and TX
Levels
-7.5 to 7.5dB
Subaudio
Filter
Output
Enable
RXIN
Subaudio
Filter
Input
Select
LPF1
LPF2
HPF
Subaudio
HPF/LPF
Select
AUX Output
CTCSS encode
Band Gap
Reference
Control
1
audio tone encode
AUX
Task
0
CTCSS decoders
Control with
Initialization Tasks
External DC
Restoration
VBIAS
to Modulation
Control Block
External DC
Restoration
Figure 15: Subaudio Block Diagram
¤2001 MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480221.002
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.
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