FSK Modem and DTMF Codec
CMX865
5.10.3 Transmit Mode Register
Transmit Mode Register: 16-bit write-only.
C-BUS address $E1
This register controls the CMX865 transmit signal type and level. All bits of this register are cleared to 0
by a General Reset command, or when b7 (Reset) of the General Control Register is 1.
15
0
14
13
12
11
10
9
8
0
7
0
6
0
5
0
4
3
2
1
0
Bit:
Tx mode =
modem
Tx level
Start-stop /
synch data
# data bits /
synch data source
0
0
Tx mode =
Tx level
0
DTMF Twist
DTMF or Tone select
DTMF/Tones
Tx mode =
Disabled
Set to 0000 0000 0000
Tx Mode Register b15: Reserved, set to 0
Tx Mode Register b14-12: Tx Mode
These three bits select the transmit operating mode.
b14 b13 b12
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
Bell 103 300bps FSK
“
V.23 FSK
“
Bell 202 FSK
“
DTMF / Tones
Transmitter disabled
High band (Answering modem)
Low band (Calling modem)
1200bps
75bps
1200bps
150bps
Tx Mode Register b11-9: Tx Level
These three bits set the gain of the Tx Level Control block.
b11
b10
b9
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
0dB
-1.5dB
-3.0dB
-4.5dB
-6.0dB
-7.5dB
-9.0dB
-10.5dB
Tx Mode Register b8: Reserved, set to 0
© 2005 CML Microsystems Plc
20
D/865/3
CMLMICRO [ CML MICROCIRCUITS ]
