Low Power V.32 bis Modem
CMX869
Tx Mode Register b6-5: Modem Modes - Reserved, set to 00
Tx Mode Register b4-3: Tx Modem Data format
These two bits select Special or Start-stop mode and the addition of a parity bit to transmitted
characters in Start-stop mode.
b4
b3
1
1
0
0
1
0
1
0
Special modes (see below)
Start-stop mode, no parity
Start-stop mode, even parity bit added to data bits
Start-stop mode, odd parity bit added to data bits
Tx Mode Register b2-0: Tx Modem Data and Stop bits (Start-Stop modes)
In Start-stop mode these three bits select the number of Tx data and stop bits.
b2
b1
b0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
8 data bits, 2 stop bits
8 data bits, 1 stop bit
7 data bits, 2 stop bits
7 data bits, 1 stop bit
6 data bits, 2 stop bits
6 data bits, 1 stop bit
5 data bits, 2 stop bits
5 data bits, 1 stop bit
Tx Mode Register b2-0: Tx Modem Data source (Special modes)
When b4-3 = 11 bits 2-0 select the source of the Transmitted data as below:
b2
b1
b0
1
1
1
0
0
0
0
1
1
0
1
1
0
0
1
0
x
1
0
1
0
Synchronous , data bytes taken directly from the Tx Data Buffer
Reserved, do not use.
Reserved, do not use.
Continuous 1s
Continuous 0s
Continuous alternating 1s and 0s
Reserved, do not use.
Tx Mode Register b8: DTMF/Tones Mode - Reserved, set to 0
Tx Mode Register b7-5: DTMF Twist (DTMF mode)
These 3 bits allow for adjustment of the DTMF twist to compensate for the frequency response of
different external circuits. The device varies the twist by making changes to the upper tone group
levels. Note that the twist cannot be adjusted mid-tone.
b7
b6
b5
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
+2.0dB twist – normal setting when external response is flat
+1.0dB twist
+1.5dB twist
+2.5dB twist
+3.0dB twist
+3.5dB twist
+4.0dB twist
+4.5dB twist – do not use in conjunction with the 0dB Tx level setting
© 2004 CML Microsystems Plc
23
D/869/4
CMLMICRO [ CML MICROCIRCUITS ]
