ACE9040 datasheet(23/33 Pages) MITEL

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ACE9040

filter, the output buffer includes a clock rejection filter. The cut-

off frequencies are programmed by bits DATAF[1:0] in the

“Initializing mode 1” control message. Filtered data passes

through the mute switch DATM and a variable gain stage

DATADEV with a range of – 2·8 to + 3·2 dB to set the required

level of deviation. The mute switch is controlled by bit DATM

in the “Operation mode” control message. DATADEV is

controlled by bits DATD[3:0] in the “Initialising Mode 1” control

message. The data signal is buffered out to pin DATO to drive

the modulation combiner.

DTMF

DTMF tones are generated when commanded via the

serial interface and conform to the standard CCITT

frequencies. All 16 standard tone pairs or any individual tone

can be generated. To select DTMF tones data bits for

transmission DTMFEN, DTMFMODE[1:0] and DTMF[3:0]

need to be set using an “Operation mode” control message.

Data bits DTMFMODE[1:0] select low, high or both tones of

the pair as shown in table 6. Bits DTMF[3:0] select the tone

pair as shown in table 7. DTMFEN set to “1” enables DTMF

operation. To change DTMF tones, an “Operation mode”

control message with DTMFEN set to “0” must be sent to

cancel the previous selection as the DTMF tone can only be

changed when DTMFEN=0.

This prevents any spurious

tones being generated.

An optional pre-emphasis of 2 dB of the high frequency

tone group above the level of the low frequency group is

enabled by bit DTWIST in the “Initializing mode 0” control

message.

DTMF tones can be selected to replace the speech in

either or both the transmit and receive paths. In the transmit

path setting bit DTMFM to “1” as in the “Operation mode”

control message will connect the DTMF signal to INPSENSE

gain adjustment block’s input in place of the speech signal. In

the receive path setting bit TONEM to “1” in the “Operation

mode” control message will connect the DTMF signal to the

input to RXSENSE gain adjustment block in place of the

speech input at pin RXI. In each case the DTMFEN bit must

also be “1”.

DTMF signals are generated as sinewaves by an internal

digital to analog converter and are smoothed by the transmit

and receive filters. DTMF waveforms start and stop at a zero

crossing to avoid transients in the filters and to limit their

bandwidth. The DTMF signal is brought out directly on pin

DTMF without further buffering.

The DTMF generator is powered down whenever a tone

is not being generated, by setting DTMFMODE[1:0] to “00”.

Re-transmitted SAT

ACE9040 provides two alternative paths for Supervisory

Audio Tones (SAT). The first of these re-transmits the

received SAT tone to the base station after narrow band

filtering and providing signal level adjustment. This path is

selected by setting SATS bit to “0” in the “Initializing mode 1”

control message. The baseband signal from the receiver FM

discriminator drives the ACE9040 through the RSI pin into the

RXSAT 6 kHz bandpass filter required for AMPS or TACS.

The recovered SAT signal then passes through a 10 dB

amplifier and the SATS selector switch to the deviation setting

amplifier SATDEV. This is controlled by bits SATD[4:0] in the

“Initializing mode 0” control message. SAT then passes

through the SATM mute switch, controlled by bit SATM in the

“Operation mode” control message, to output pin TSO for

input to the modulation combiner.

Regenerated SAT

The alternative SAT path externally measures the SAT

frequency and generates a local tone to match. This route is

TRANSMIT & RECEIVE SAT PATHS

Fig. 13 Transmit and Receive SAT Paths.

RSI

TSI

VMID

SATDEV

RSO

TSO

SCHMITT

RXSAT

6kHz FILTER

TXSAT

6kHz FILTER

-12dB

-15dB

10dB

SATM

SATS

-4.5 to +4.8dB

SATD[4:0]

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