FSK Modem and DTMF Codec
CMX865
Tx Mode Register b3-0: DTMF/Tones Mode
If DTMF/Tones transmit mode has been selected (Tx Mode Register b14-12 = 001), then b7-5
should be set to 000 and b4-0 will select a DTMF signal, a fixed tone or one of four programmed
tones or tone pairs for transmission.
b4 = 0: Tx fixed tone or programmed tone pair
b3
b2
b1
b0 Tone frequency (Hz)
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
No tone
697
770
852
941
1209
1336
1477
1633
1300
2100
2225
(Calling tone)
(Answer tone)
(Answer tone)
Programmed Tx tone or tone pair, see 5.10.8
Tone pair TA
Tone pair TB
Tone pair TC
Tone pair TD
“
“
“
b4 = 1: Tx DTMF
b3
b2
b1
b0
Low frequency (Hz)
High frequency (Hz)
Keypad symbol
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
941
697
697
697
770
770
770
852
852
852
941
941
941
697
770
852
1633
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
1633
1633
1633
D
1
2
3
4
5
6
7
8
9
0
*
#
A
B
C
© 2005 CML Microsystems Plc
22
D/865/3
CMLMICRO [ CML MICROCIRCUITS ]
