CMX138 CML Microcircuits, CMX138 Datasheet - Page 54

• Manufacturer Part Number: CMX138
• Description: Audio Scrambler and Sub-Audio Signalling Processor
• Manufacturer: CML Microcircuits

Audio Scrambler and Sub-Audio Signalling Processor
$C8 (P2.2-3)
These words set the User Defined DCS code to be transmitted or searched for. The least significant bit
(bit 0) of the DCS code is transmitted or compared first and the most significant bit is transmitted or
compared last. Note that DCS Data bit 23 is only used when bit 11 (DCS 24) of P2.1 is set to ‘1’.
$C8 (P2.4)
Calculate the values of N and R for the desired CTCSS frequency by:
Eg: for 150.1Hz, N=36, R=1 so P2.4 = $6901
$C8 (P2.5)
The Sub-audio Drop Out Time defines the time that the sub-audio signal detection can drop out before
loss of sub-audio is asserted. The period is set according to the formula:
The setting of this register defines the maximum drop out time that the device can tolerate. The setting of
this register also determines the de-response time, which is typically 90ms longer than the programmed
drop out time.
$C8 (P2.6)
© 2008 CML Microsystems Plc
P2.2
P2.3
P2.5
P2.4
P2.6
Bit:
Bit:
Bit:
Bit:
15
15
0
0
0
15
15
N = integer (0.24 * User Frequency)
R = round (((0.24 * User Frequency) – N) * 3000 / User Frequency) + 0.5
0
0
Time = Sub-audio Drop Out Time × 8.0ms
14
14
DCS CODE (LOWER) and DCS CODE (UPPER)
1
1
User Defined CTCSS Tone
Sub-audio Drop Out Time
1
Reserved – do not access
14
14
1
1
13
13
1
1
1
13
13
1
1
12
12
0
0
0
12
12
0
0
Sub-audio Drop Out Time
11
11
11
11
User Defined CTCSS code N
10
10
10
10
9
9
9
9
Page 54
8
8
8
8
DCS Data (bits 23/22-12)
Reserved – set to $000
7
7
7
7
DCS Data (bits 11-0)
6
6
6
6
5
5
5
5
User Defined CTCSS Code R
[range 0 to 120ms]
4
4
4
4
0
3
3
3
3
2
2
2
2
D/138_FI1.0/5
1
1
1
1
CMX138
0
0
0
0