CMX635 查看數據表（PDF） - CML Microsystems Plc

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CMX635

ISDN Subscriber Processor

CML Microsystems Plc 

ISDN Subscriber Processor

CMX635

1.5.4

The G.711 Codec and Analogue Gain Path

The PCM Codec-Filter performs voice digitisation and reconstruction and incorporates encoder

bandpass and decoder lowpass filters with pre and post-filtering and with selectable A-law and µ-

law companding. In each case the coder and decoder process a companded 8-bit PCM word

following CCITT recommendation G.711 for A-law and µ-law conversion. The encoder bandpass

filter and decoder lowpass filter provides passband flatness and stopband rejection according to

CCITT recommendation G.712. The lowpass filter contains the required (Sin X)/X compensation.

Flexible receive and transmit digital gain control and analogue routing controls are provided to

enable configuration into POTS or ISDN feature-phone applications.

Examples of the possible configurations for POTS are:

• Sine, Square or Trapezoid ring frequency routed to speaker output with programmable

amplitude. Cadence controlled within CMX635 or externally.

• Received analogue Codec signal routed to earpiece output (SLIC/Hybrid input).

• Call progress or DTMF tones summed with or replacing Codec signal to earpiece at

programmable amplitude.

• Call Waiting Tone (SAS), Caller Line ID on Call Waiting alert signal (CAS) and FSK

caller ID data replacing signal to earpiece at programmable amplitude.

• Received DTMF tones from receive Codec routed to DTMF decoder for remote

signalling detection.

• DTMF tones from POTS interface routed to DTMF decoder for dialled number

detection.

Examples of the possible configurations for ISDN phones are:

• Input from 1 of 2 microphone inputs switchable through programmable gain to transmit

Codec. Allows transducer matching and A.G.C. function for speakerphone operation.

• Independent programmable microphone channel attenuation for speakerphone

algorithms.

• Received analogue Codec signal routed to earpiece and/or loudspeaker output.

Loudspeaker amplifier has programmable gain for volume control and speakerphone

attenuation.

• Programmable proportion of microphone channel can be added to earpiece output as

“sidetone”.

• DTMF tones can be routed to earpiece/speaker for dialling feedback or to transmit

Codec for remote DTMF signalling.

• Full range of pre-programmed tones can be routed to speaker at programmable

amplitude for ringing.

The Programming Guide, section 1.6, details the full range of routing and gain control functions

available.

1.5.5 The Tone Generator and Tone Decoder

The Tone Generator can be used to generate tones for either DTMF tones, call progress tones,

ringing signals for ISDN phones and FSK data tones for POTS caller ID functions.

The tones available are pre-programmed and grouped into 4 tone fields of up to 256 tones each.

To select a particular tone or tone pair the ‘Tone/Codec Control’ register is first written with the

required tone field and the ‘Tone’ register is then written with the selection from that field. The

Tone Enable register allows independent power save control for the various tone types.

The Ring signal can be configured as a sine, square or trapezoidal output at a number of

frequencies between 17Hz and 51Hz.

© 2001 Consumer Microcircuits Limited

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D/635/2

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