Baseband Processor For Mixed Mode Land Mobile Radio
CMX880
B11
0
Mismatches allowed
No predefined limit
B13
X
B12
X
(reliant only on threshold)
1
1
1
1
0
2
4
6
0
0
1
1
0
1
0
1
Note: A single 'mismatch' is defined as the difference between two adjacent symbol levels, thus if the symbol '+1'
were expected, then received symbol values of '+3' and '-1' would count as 1 mismatch, a received symbol value
of '-3' would count as 2 mismatches. A setting of '2 mismatches' is recommended for normal use.
$C8 (B1.10)
TX C4FM/CQPSK UNIT LEVEL
Bit:
15
0
14
0
13
0
12
11
10
9
8
7
6
5
4
3
2
1
0
Unit Level (+ve)
The CMX880 derives the 4 C4FM symbol levels to be transmitted from the unit level programmed into the ‘TX
C4FM Unit Level’ register.
Symbol level
+3
+1
- 1
- 3
Unit level ´ +3
Unit level ´ +1
Unit level ´ - 1
Unit level ´ - 3
The value programmed into the ‘TX C4FM Unit Level’ register is derived using the formula:
65336 ´ ‘Unit Level’ (V) / VDD
For optimum performance it is recommended that the FM modulator be set up so that the value programmed in
the TX C4FM Unit Level register is close to 2048.
$C8 (B1.11)
SELCALL TONE BW AND SIGNAL LEVEL
Bit:
15
0
14
0
13
0
12
0
11
0
10
0
9
8
7
6
5
4
3
2
1
0
Signal Detection Level
[range: 0 - 63]
Selcall Tone BW
The ‘Signal Detection Level’ bits (bits 9 to 4) set the minimum Selcall and/or FFSK signal level that will be
detected. The levels are set according to the formula:
‘Signal Detection Level’ ´ VDD(A)/1024
[4.88mV per LSB at VDD(A)=5V]
The detected tone bandwidth is set in accordance with the following table:
BANDWIDTH
Bit 3
Bit 2
Bit 1
Bit 0
Will Decode
Will Not Decode
±2.4%
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
±1.1%
±1.3%
±1.6%
±1.8%
±2.0%
±2.2%
±2.5%
±2.7%
Recommended for CCIR
Recommended for ZVEI
±2.7%
±2.9%
±3.2%
±3.5%
±3.7%
±4.0%
±4.2%
ã 2001 Consumer Microcircuits Limited
61
D/880/1
CMLMICRO [ CML MICROCIRCUITS ]
