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FM214

9600/14400 bps MONOFAX Modem Family

Conexant Systems 

 

 


Technical Specifications

Configurations, Symbol Rates and Data Rates

The selectable modem configurations, along with the

corresponding symbol (baud) rates and data rates, are

listed in Table 2.

Scrambler/Descrambler

The modem incorporates a self-synchronizing

scrambler/descrambler in accordance with ITU-T V.33,

V.17, V.29, and V.27 ter recommendations, depending

upon the selected configuration.

Data Encoding

The data encoding conforms to ITU-T

recommendations V.33, V.17, V.29, V.27 ter, V.21

Channel 2, and V.23.

Fixed Digital Cable Compromise Equalizer

Compromise equalization can improve performance

when operating over low quality lines. The modem has

a selectable fixed digital compromise cable equalizer

in the high speed receive and transmit data path.

Transmitted Data Spectrum

The transmitted data spectrum is shaped in the

baseband by an excess bandwidth finite impulse

response (FIR) filter with the following characteristics:

When operating at 2400 baud, the transmitted

spectrum is shaped by a square root of 20% raised

cosine filter.

When operating at 1600 baud, the transmitted

spectrum is shaped by a square root of 50% raised

cosine filter.

When operating at 1200 baud, the transmitted

spectrum is shaped by a square root of 90% raised

cosine filter.

The out-of-band transmitter energy levels in the 4 - 50

kHz frequency range are below -55.0 dBm.

Transmit Level

The transmitter output level is programmable in the

DSP RAM from 0 dBm to -15.0 dBm and is accurate to

±1.0 dB. The modem adjusts the output level by

digitally scaling the output to the transmitter's digital-

to-analog converter.

Turn-on Sequence

Transmitter turn-on sequence times are shown in

Table 3.

Receive Dynamic Range

The receiver satisfies PSTN performance

requirements for received line signal levels from 0

dBm to -43 dBm measured at the Receiver Analog

Input (RXA) input. An external input buffer must be

supplied between RXA and LINEIN.

The default values of the programmable Received

Line Signal Detector (RLSD#) turn-on and turn-off

threshold levels are -43 dBm and -48 dBm,

respectively. The RLSD# threshold levels can be

programmed over the following range:

Turn on: -10 dBm to -47 dBm

Turn off: -10 dBm to -52 dBm

Automatic Adaptive Equalizer

An adaptive equalizer in ITU-T V.33, V.17, V.29 and

V.27ter modes compensates for transmission line

amplitude and group delay distortion.

Receiver Timing

The timing recovery circuit can track a ±0.01%

frequency error in the associated transmit timing

source.

Carrier Recovery

The carrier recovery circuit can track a ±7 Hz

frequency offset in the received carrier.

Turn-off Sequence

Transmitter turn-off sequence times are shown in

Table 4.

Clamping

Received Data (RXD) is clamped to a constant mark

whenever RLSD# is off.

V.23 Full-Duplex Features

The modem can transmit and detect Break signals

(continuous Space).

The Mark and Space frequencies are 1300 and 2100

Hz, respectively, for 1200 bps, and 390 and 450 Hz,

respectively, for 75 bps.

Additional features include an optional host

programmable Receive Compromise Equalizer for

V.23 1200 bps reception and Caller ID mode.

Default transmitter turn-on/turn-off sequence times are

10.5 ms (RTS On to CTS On) and 2.2 ms (RTS Off to

CTS Off).

4

MD205

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