CMX138 CML Microcircuits, CMX138 Datasheet - Page 52

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

Audio Scrambler and Sub-Audio Signalling Processor
9.2.1
9.2.2
Default values:
$C8 (P1.0)
Bits 11 (MSB) to 1 (LSB) set the transmitted In-band tone, Audio Tone (pk-pk) with a resolution of
AV
care as higher values may result in signal “clipping”.
Bit 0 controls In-band tone de-emphasis. When In-band tones are enabled in the Mode Control register
($C1), de/pre-emphasis is enabled in the Audio Control register ($C2) and this bit (b0) is set to '1'; signals
going to the In-band tone detector are de-emphasised in accordance with Figure 7 of the datasheet. This
combination of settings should only be used in Rx mode. If this bit is set, then in Tx mode, the user is
advised to clear the de/pre-emphasis bit in the Audio Control register ($C2).
$C8 (P1.1)
The ‘detect threshold’ bits (bits 9 to 4) set the minimum In-band tone signal level that will be detected.
The levels are set according to the formula:
The In-band tone detected bandwidth is set in accordance with the following table:
$C8 (P1.2)
This word set the programmable In-band tone used in transmit and receive. The frequency is set in bits
11-0 according to the formula:
© 2008 CML Microsystems Plc
P1.2
P1.0
P1.1
P1.0
P1.1
P1.2
Bit:
Bit:
Bit:
DD
Recommended for EEA ⇒
Bit:
Bit:
/2048 per LSB (1.611mV per LSB at AV
Program Block 0 – reserved
Program Block 1 – In-band Tone Setup:
15
15
15
1
0
0
15
15
1
0
0
14
14
14
Audio Band Tones Tx Level
1
In-band tone Detect Bandwidth and Audio Band Detect Threshold
1
User-Programmable In-band Tone
1
14
14
1
1
1
Minimum Level = Detect Threshold × 3.993mV rms at AV
P1.0:
P1.1:
P1.2
13
13
13
0
0
0
13
13
0
0
0
12
12
12
1
1
1
12
12
1
1
1
$800
$009
$942 (1750Hz)
Bit 3
Programmable In-band Tone
11
11
1
1
1
1
11
User Programmable In-band Tone
0
11
11
0
10
10
10
0
Bit 2
10
10
0
0
0
0
0
DD
9
9
9
N (see below)
9
9
Bit 1
=3.3V). Valid range for this value is 0 to 1536 – use with
Audio band detect threshold
Page 52
0
1
1
0
Audio band tones / data Tx level
Audio band detect threshold
8
8
8
8
8
Audio band tones Tx level
Bit 0
0
1
0
1
7
7
7
7
7
6
6
6
6
6
Will Decode
±1.1%
±1.3%
±1.6%
±1.8%
5
5
5
5
5
R (see below)
BANDWIDTH
4
4
4
DD
4
4
= 3.3V
3
3
3
3
In-band tone detect
Will Not Decode
3
In-band tone detect
bandwidth
2
2
2
bandwidth
±2.4%
±2.7%
±2.9%
±3.2%
2
2
D/138_FI1.0/5
1
1
1
1
1
CMX138
Emph
Emph
0
0
0
0
0