CMX867 查看數據表（PDF） - CML Microsystems Plc

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CMX867

Low Power V.22 Modem

CML Microsystems Plc 

Low Power V.22 Modem

CMX867

1.5.3 Tx Filter and Equaliser

The FSK or DPSK modulator output signal is fed through the Transmit Filter and Equaliser block which

limits the out-of-band signal energy to acceptable limits. In 600 and 1200 bps FSK and DPSK modes this

block includes a fixed compromise line equaliser which is automatically set for the particular modulation

type and frequency band being employed. This fixed compromise line equaliser may be enabled or

disabled by bit 10 of the General Control Register. The amount of Tx equalisation provided compensates

for one quarter of the relative amplitude and delay distortion of ETS Test Line 1 over the frequency band

used.

1.5.4 DTMF/Tone Generator

In DTMF/Tones mode this block generates DTMF signals or single or dual frequency tones. In DPSK

modem modes it is used to generate the optional 550 or 1800Hz guard tone.

1.5.5 Tx Level Control and Output Buffer

The outputs (if present) of the Transmit Filter and DTMF/Tone Generator are summed then passed

through the programmable Tx Level Control and Tx Output Buffer to the pins TXA and TXAN. The Tx

Output Buffer has symmetrical outputs to provide sufficient line voltage swing at low values of VDD and

to reduce harmonic distortion of the signal.

© 2004 Consumer Microcircuits Limited

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D/867/5

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