CX06832-11 View Datasheet(PDF) -

FM336Plus

V.34/Group 3 High Performance Fax Modem Family

Supervisory Tone Detection

Three parallel tone detectors (A, B, and C) are

provided for supervisory tone detection. The signal

path to these detectors is separate from the main

received signal path.

Each tone detector consists of two cascaded second

order IIR biquad filters. The coefficients are host

programmable. Each fourth order filter is followed by a

level detector which has host programmable turn-on

and turn-off thresholds allowing hysteresis. A pre-filter

and squarer precede tone detector C. This circuit is

useful for detecting a tone with a frequency equal to

the difference between two tones that may be

simultaneously present on the line. The SQDIS bit may

disable the squarer causing tone detector C to be an

eight-order filter. The tone detectors are disabled in

data mode.

The tone detection sample rate is 9600 Hz in V.8 and

V.34 modes and is 7200 Hz in non-V.34 modes. The

default call progress filter coefficients are based on a

7200 Hz sampling rate and apply to non-V.34 modes

only. The maximum detection bandwidth is equal to

one-half the sample rate.

Auto-Dialing and Auto-Answering Control

Features are provided to allow the host to perform

auto-dialing and auto-answering. These functions

include DTMF or pulse dialing, ring detection, and a

comprehensive supervisory tone detection scheme.

The major control parameters are host programmable.

Transmitted Data Spectrum

The transmitter spectrum is shaped by raised cosine

filter functions, either the square root of 12.5% (V.34,

V.32 bis, V.32), 20% (V.17, V.33, and V.29), 50%

(V.27 ter, Bell 208), or 75% (V.22 bis, Bell 212A).

Transmit Level

The transmitter output level is selectable from 0 dBm

to –15 dBm in 1 dB steps and is accurate to ±0.5 dB

when used with an external hybrid. The output level

can also be tuned by changing a gain constant in the

modem DSP RAM. The maximum V.34 transmit level

for acceptable receive performance should not exceed

–9 dBm.

Answer Tone (-D / -D90)

When the NV25 bit is a zero, the modem generates

a 2100 Hz answer tone at the beginning of the answer

handshake for 5.0 seconds (V.8) or 3.6 seconds

(V.32 bis, V.32, V.22 bis, V.22, V.23, and V.21). The

answer tone has 180° phase reversals every 0.45

seconds to disable network echo cancellers (V.8,

V.32 bis, and V.32).

Receive Level

The modem satisfies performance requirements for

received line signal levels from 0 dBm to –43 dBm

measured at the receiver analog (TIP and RING) input

in V.17, V.33, V.29, V.27 ter, and DTMF modes. In

V.90, V.34, V.32 bis, V.32, V.22 bis, V.22, and

V.23 modes, the receive level range is from –9 dBm

(–15 dBm at RIN) to –43 dB. (RIN is 6 dB lower than

TIP and RING.)

Carrier Recovery

The carrier recovery circuit can track a ±7 Hz

frequency offset in the received carrier.

Echo Canceller (-D / -D90)

A data echo canceller with near-end and far-end echo

cancellation is included for 2-wire duplex V.90/V.34/

V.32 bis/V.32 operation. The combined echo span of

near and far cancellers can be up to 40 ms. The

proportion allotted to each end is automatically

determined by the modem. The delay between near-

end and far-end echoes can be up to 1.2 seconds.

4

Conexant

101361A

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