CMX883(2002) 데이터 시트보기 (PDF) - CML Microsystems Plc
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CMX883 Datasheet PDF : 54 Pages
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FRS Signalling Processor
CMX883
1.5.3.4 Receiving and Decoding In-band Tones
In-band tones can be used to flag the start of a call or to confirm the end of a call. If they occur during a
call the tone may be audible at the receiver. When enabled, an interrupt will be issued when a signal
matching a valid In-band tone is detected and when a present In-band tone turns off or changes (i.e. at
the start and at the end of each In-band tone).
The CMX883 implements QTC coding using the EEA tone set. Other addressing and data formats can
be implemented but will require more host intervention. The custom tones (1-4) permit other audio tones
to be encoded or decoded, the frequency of each tone is defined in the program registers P1.2-5.
In receive the CMX883 scans through the tone table sequentially, the code reported will be the first one
that matches the incoming frequency.
Adjustable decoder bandwidths, threshold levels are programmable via the Programming register and
permits certainty of detection and signal to noise performance to be traded when congestion or range
limits the system performance. The In-band signal is derived from the received input signal after the
band pass filtering shown in Figure 5.
Table 5 In-band Tones
Special / Information Tones
(5th bit = 0)
4 bit Code
Freq.
Dec Hex
(Hz)
00
No Tone
1
1 Custom Tone 0 P1.21
2
2 Custom Tone 1 P1.31
3
3 Custom Tone 2 P1.41
4
4 Custom Tone 3 P1.51
55
66
77
88
99
10 A
Reserved
11 B
12 C
13 D
14 E
15 F
Normal Tones
(5th bit = 1)
4 bit Code
Freq.
Dec Hex
(Hz)
0
0
1981
1
1
1124
2
2
1197
3
3
1275
4
4
1358
5
5
1446
6
6
1540
7
7
1640
8
8
1747
9
9
1860
10 A
1055
11 B
930
12 C
2247
13 D
14 E
991
21102
15 F
No Tone
Notes:
1 Special tones 1-4 provide user programmable tone options for both transmit and receive modes
as set in the indicated Program register, for programming information see section 1.6.20.2.
2 Normal tone 14 is the repeat tone, this code is must be used in transmit when the new code to
be sent is the same as the previous one. e.g. to send ‘333’ the sequence ‘3R3’ should be sent,
where ‘R’ is the repeat tone. When receiving Selcall tones the CMX883 will indicate the repeat
tone when it is received, it is up to the host to interpret this and decode tones accordingly.
© 2002 CML Microsystems Plc
20
D/883/2
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