PMR Signalling Processor
CMX881
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 Selcall signal is derived from the received input signal after the band
pass filtering shown in Figure 5.
Table 5 lists the Selcall codes available, these are 5 bit numbers set or reported in: Tx Tone register
($C3) and Tone Status register ($CC).
Table 5 Selcall Tones
Special / Information Tones
Normal Tones
(5th bit = 1)
(5th bit = 0)
4 bit Code
Frequency set in
Program register:
No Tone
4 bit Code
Dec Hex
Frequency set in
Dec Hex
Program register:
0
1
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
P1.31
P1.41
2
2
P1.51
3
3
P1.61
4
4
P1.71
5
5
P1.81
6
6
P1.91
1-13
7
7
P1.101
P1.111
P1.121
P1.131
P1.141
P1.151
P1.161
P1.171
P1.181
Reserved
8
8
9
9
10
11
12
13
14
15
10
11
12
13
14
15
P1.21,2
Reserved
Notes:
1
Special tone 14, and Normal tones 0 - 15 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. To ensure correct operation tones should not be programmed
with overlapping detect bandwidths.
2
Special tone 14 is the repeat tone, this code 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 CMX881 will indicate the repeat
tone when it is received, it is up to the host to interpret this and decode tones accordingly.
2004 CML Microsystems Plc
20
D/881/7
CMLMICRO [ CML MICROCIRCUITS ]
