CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
6.4.2 Tone Signaling Processor
The Tone Signaling Processor, shown in Figure 31, provides a unique combination of features that
outperforms traditional approaches. It supports traditional subaudio CTCSS tones with advanced, flexible,
encode and decode functions to simplify radio designs and enable new FRS radio features. The tone
signaling processor can also generate audio tones suitable for call alert signals to eliminate the need for an
external tone generator, if desired. Internal signals are exposed via flexible switch paths to support user
defined external circuits. Features include:
• 51 parallel CTCSS decoders can be individually enabled/disabled to perform ‘flash’ tone decoding on
user activated tones in an internal tone ‘watch list.’ This architecture provides the performance to support
rapid receive tone scanning, group calling and Tone Cloning™ (automatic CTCSS decoder configuration)
end product functions without a decoder response time penalty. Note that one tone must be applied to the
decoders at any given time, consistent with normal CTCSS practice.
• The CTCSS encoder/decoder contains a pre-programmed set of 50 tone definitions. Each tone is
referenced by index for simple application program development. The 50 tone definitions include the
entire TIA-603 standard tone set with other common frequencies added. A 51st User Programmable tone
allows a user to configure an arbitrary tone frequency.
• Integrated voltage reference regulates CTCSS encoder output level for constant subaudio RF deviation
without requiring an external voltage regulator.
• Digitally controlled subaudio output level to support various external radio modulation architectures.
• Complete CTCSS decoder status word provides a single Decoder Status bit to directly drive squelch
control decisions in an external µC.
• User configurable CTCSS decoder Notone timer (to adjust CTCSS decoder dropout response),
bandwidth (to adjust selectivity) and TX duration timer functions.
• High performance filters with selectable gain controls enhance end product radio sensitivity and support
multiple design architectures e.g. both internal and external summing of subaudio and audio signals.
• Audio tone generator for call alert signals.
• Controllable switch paths and internal signal exposure to support user developed functions.
AUX I/O 2
audio call
tone output
from the
discriminator
RXIN 1
BPF
LPF
CTCSS encode
audio tone encode
1
0
CTCSS decoders
voltage
ref
subaudio
output
Vbias
Figure 31: Tone Signaling Processor
2003 CML Microsystems Plc
50
D/838/8
Share Link: 
