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
4.2.3 CTCSS Subaudio Decoder and Encoder Tone Set
The CMX838 supports all popular subaudio tones with a unique, full performance, 'one-of-any' rapid detect
capability that adds support for end product group calling and Tone Cloning™ features. The digital processor
essentially contains 51 decoders to analyze the receive signal. Each decoder can independently be enabled
or disabled via configuration tasks.
The result of the subaudio signal analysis is available in the subaudio status register ($94). Both a decode
status bit, and a decoder index number are reported in the status register. The decode status bit is a logic one
when an enabled decoder senses that the input signal matches its center frequency – the index number will
be that of the matching decoder.
If the input signal does not contain a subaudio signal that matches an enabled decoder’s center frequency
then the status bit is a logic zero – in this case the decoder index number is reported as:
A. 62 if there is a significant subaudio frequency present.
B. 63 if the no tone timer has expired indicating there is no significant subaudio frequency present now.
C. 0 if no subaudio signal has been seen since the subaudio processor was enabled or most recently placed
in RX mode.
D. Any enabled index, if the last frequency measurement indicates that enabled tone may be present but
has not yet been fully qualified.
In TX mode the subaudio status is normally 0 and becomes 127 to indicate that the TX timer timed out.
No. Frequency (Hz)
No. Frequency (Hz)
1.
67.0
27.
159.8*
2.
69.3
28.
162.2
3.
71.9
29.
165.5*
4.
74.4
30.
167.9
5.
77.0
31.
171.3*
6.
79.7
32.
173.8
7.
82.5
33.
177.3*
8.
85.4
34.
179.9
9.
88.5
35.
183.5*
10.
91.5
36.
186.2
11.
94.8
37.
189.9*
12.
97.4
38.
192.8
13.
100.0
39.
196.6*
14.
103.5
40.
199.5*
15.
107.2
41.
203.5
16.
110.9
42.
206.5*
17.
114.8
43.
210.7
18.
118.8
44.
218.1
19.
123.0
45.
225.7
20.
127.3
46.
229.1*
21.
131.8
47.
233.6
22.
136.5
48.
241.8
23.
141.3
49.
250.3
24.
146.2
50.
254.1*
25.
151.4
51. User Programmable
26.
156.7
* Subaudible Tones not included in TIA-603 standard
Table 2: CTCSS Subaudio Tone Frequencies with their Corresponding Index Number
2003 CML Microsystems Plc
20
D/838/8
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