Marine VHF Audio and Signalling Processor
CMX885
Table 3 DTMF Tone Pairs
Low Tone
High Tone
(Hz)
Tone Code (Hex) Key Pad Position
(Hz)
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0
1
2
3
4
5
6
7
8
9
0
*
#
A
B
C
D
697
697
697
770
770
770
852
852
852
941
941
941
697
770
852
941
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
1633
1633
1633
1633
Note: Only the underlined tone is generated when the 'Single Tone' bit is enabled.
7.7
DSC modem - (FSK 1200bps)
The device can implement a 1200 bps DSC (Digital Selective Call) modem conforming to the
requirements of ITU-R M.493-11 for use in Marine VHF band radio equipment. This modem uses tones at
1300Hz and 2100Hz to represent binary 1’s and 0’s respectively, with 6dB/octave pre-emphasis in Tx.
See:
o
o
o
o
Mode Control – $C1 write
Modem Configuration – $C7 write
Rx Data 1 – $C5
Tx Data 1 – $CA write
DX/RX
A
B
C
D
E
F
G
H
I
Tele-
command
Message
Format
Specifier
Called Party
Address
Self-
identification
Frequency
Message
Frequency
Message
End of
Sequence
Error-check
Character
Category
Dot
Pattern
Phasing
Sequence
3 identical
DX
characters
2 Identical
characters
5 characters
1 character
5 characters 2 characters 3 characters 3 characters
1 character
1 RX
character
D
X
D
X
D
X
D
X
D
X
D
X
A
A
B
l
B
2
B
3
R
4
B
5
C
D
l
D
2
D
3
D
4
D
5
E
l
E
2
F
l
F
2
F
3
G
l
G
2
G
3
H
I
H
H
Dot pattern
R
X
7
R
X
6
R
X
5
R
X
4
R
X
3
R
X
2
R
X
1
R
X
0
A
A
B
l
B
2
B
3
B
4
B
5
C
D
1
D
2
D
3
D
4
D
5
E
l
E
2
F
l
F
2
F
3
G
l
G
2
G
3
H
I
Figure 11 DSC format
To enable this mode, the En_DSC bit of the Modem Configuration register $C7:b11 must be set. The
DSC modem itself can then be controlled by setting or clearing the Modem Enable bit $C1:b2, after
© 2010 CML Microsystems Plc
24
D/885/3
CMLMICRO [ CML MICROCIRCUITS ]
