RALCWI Vocoder
CMX608/CMX618/CMX638
Mode 1
Mode 2
The DTMF 4-bit number is detected from the DTMF data frame. The 4-bit code is made
available in the DFRAMEDATA register ($37) and is also re-synthesized as a tone at the
output. This mode is enabled by setting bits 5 and 6 in the VCTRL register ($11) to '1'.
The DTMF 4-bit number is detected from the DTMF data frame. The 4-bit code is made
available in the DFRAMEDATA register ($37) andsilence is output from the Codec. This
mode is enabled by setting bit 5 in the VCTRL register ($11) to '1' and by setting bit 6 in the
VCTRL register to '0'.
The DTMF generators and detectors are provided so that commonly encountered tones can be
reproduced naturally at the other end of a Vocoded link, rather than being interpreted as a form of speech.
They should not be relied upon to provide an error free method of relaying tone signalling to other
decoders, such as a telephone exchange DTMF detector, for example.
5.7.3.
DTMF Format
The DTMF format is selected by bit 7 in the (Vocoder Configuration) VCFG register ($07), according to the
following tables:
Format 1 This format is used when bit 7 of the VCFG register ($07) is cleared to '0'.
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
Symbol
D
1
2
3
4
5
6
7
8
9
0
*
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
#
A
B
C
1
1
0
1
1
1
1
0
1
1
1
1
Table 2 DTMF - Format 1
2014 CML Microsystems Plc
27
D/608_18_38/11
CMLMICRO [ CML MICROCIRCUITS ]
