V22 and Bell 212A Modem
CMX644A
TX TONES Register ($E1)
This register is used to transmit both DTMF and modem progress tones.
TONESEL
(Bit 7)
TONE/NOTONE
(Bit 6)
This bit selects the “Answer Tone” frequency in the receive detector. A
‘0’ selects 2225Hz and a ‘1’ selects 2100Hz.
This bit should be used to begin and end the transmission of tones once
the required frequency has been programmed. When set to ‘1’ the tone
will be transmitted; when set to ‘0’ a Notone (Bias Voltage) will be
generated.
When this bit is set to ‘1’ the device is configured for DTMF. When it is
set to ‘0’ the device is configured to transmit modem progress tones.
For normal DTMF operation this bit should be set to ‘0’. For test
purposes it can be set to ‘1’ in order to select the tone frequencies
individually.
DTMF/MODEM TONES
(Bit 5)
DTMF/SNGL
(Bit 4)
The following table shows the settings required for transmitting DTMF (Bit 5 should be set to ‘1’. Bits 6 and 7
should be operated as described above).
Lower Freq. (Hz)
(setting Bit 4 = 0)
941
697
697
697
770
770
770
852
852
852
941
941
941
697
770
852
Upper Freq. (Hz)
(setting Bit 4 = 0)
1633
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
1633
1633
1633
Keypad
symbol
D
1
2
3
4
5
6
7
8
9
0
*
#
A
B
C
Single Tone Freq.
(Hz)
(setting Bit 4 = 1)
1633
1209
1336
1477
1209
1336
1477
1209
852
852
941
941
941
697
770
852
D3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
The following table shows the settings required for transmitting modem progress tones. (Set Bit 4 to ‘0’ and
Bit 5 to ‘0’. Bits 6 and 7 should be operated as described earlier).
D3
0
0
0
0
0
D2
0
0
0
0
1
D1
0
0
1
1
0
D0
0
1
0
1
0
Frequency (Hz)
550
1300
1800
2100
2225
Tone
Description
Guard
Calling
Guard
Answer
Answer
©
2000
Consumer Microcircuits Limited
12
D/644A/6
CMLMICRO [ CML MICROCIRCUITS ]
