CMX624D5 CML Microcircuits, CMX624D5 Datasheet - Page 9

• Manufacturer Part Number: CMX624D5
• Description: V.23/Bell 202 modem
• Manufacturer: CML Microcircuits

V23 / Bell 202 Modem
Bell 202 mode (bit 7 of SETUP register = ‘1’):
When bit 7 of the TX TONES Register is set to ‘1’, the block generates DTMF tone pairs or single tones from
the DTMF range as shown in the table below. Bit 6 of the TX TONES Register is then used to enable or
disable the block’s output to the Tx filter.
1.5.7
This stage attenuates out of band signals present at the output of the FSK/DTMF modulator and also includes
a programmable 3dB level switch, selected by bit 2 of the FSK MODE Register.
The nominal output levels at the TOP pin when V
These levels are proportional to V
depend on the external circuitry as described in Section 1.6.1. Using the external components recommended
in Section 1.6.1 for a nominal FSK transmit level of -9dBm, DTMF tone levels of -8dBm and -6dBm, then the
out of band energy sent to the line will be within the limits shown in Figure 5 for both FSK and DTMF signals.
2001 Consumer Microcircuits Limited
Transmit Filter
TX DATA Register Bits
FSK MODE Reg
D3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Bit 1
0
1
1
Register bit 2
1 (high level)
D2
0 (low level)
FSK MODE
0dB = 775mVrms
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0 - 3
Bit 0
0
1
x
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
FSK / DTMF Modulator block output
Disabled (o/p held at V
DD
Frequency (Hz)
(Bit 7 of TX TONES = ‘0’)
, and the actual transmit signal levels present on the 2- or 4-wire line will
FSK Signal
Lower
941
697
697
697
770
770
770
852
852
852
941
941
941
697
770
852
-6dB
-3dB
1200bps FSK
(TX TONES Register Bit 4 = ‘0’)
150bps FSK
DD
DTMF Tone Pairs
9
= 5.0V are as shown below.
Frequency (Hz)
DD
Upper
1633
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
1633
1633
1633
/ 2)
DTMF Tone
(Low group)
-5dB
-2dB
‘0’ (Space)
Keypad
Legend
2200Hz
FSK Signal Frequency
487Hz
D
C
A
B
1
2
3
4
5
6
7
8
9
0
#
*
-
(High group)
DTMF Tone
Frequency (Hz)
-3dB
0dB
Single Tone
Single Tone
(Bit 4 = ‘1’)
‘1’ (Mark)
1200Hz
1633
1209
1336
1477
1209
1336
1477
1209
387Hz
852
852
941
941
941
697
770
852
-
CMX624
D/624/6