Audio Signaling Processor

7

MX803A PRELIMINARY INFORMATION

© 1996 MX•COM, INC.

Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054

Doc. # 20480122.003

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BIAS

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TONE 2 OUT

TONE 1 OUT

SUM IN

FROM MX806A

MAIN PROCESS OUT

AUDIO SWITCH IN

AUDIO SWITCH OUT

CAL/CUES OUT

SWITCHED SUM OUT

SUM OUT

SUMMING

AMPLIFIER

TO MX806A

CALIBRATION IN

CAL

CUES

TO MX806A

SUM IN

MX803A

Figure 3: Example of Signal Switching in a DBS800 microcircuit

4. General Description

4.1 DESCRIPTION

The MX803A is an audio signaling processor that provides inband tone signaling capabilities for LMR and other Radio

systems. A low-power CMOS device, the MX803A is a member of the DBS800 (Digitally integrated Baseband Sub-

system) IC family (See section 4.2). Supported Signaling systems include SelCall (CCIR, EEA, ZVEI I, II, and III) 2-Tone

SelCall and DTMF encode. The use of a non-predictive decoder and a versatile encoder, allows the MX803A to operate

in any standard or non-standard tone system.

The MX803A is a full-duplex device for use with Single Tone or Selective Call systems. The MX803A consists of a tone

decoder with a programmable NOTONE timer, two individual tone encoders and a programmable TX period timer, and an

on-chip summing amplifier. Under the control of a

µC, the MX803A will simultaneously encode and transmit 1 or 2 audio

tones in the 208-3000Hz range, as well as detect, decode, and indicate the frequency of any non-predicted input tone in

the frequency range of 313 to 6000Hz.

A general purpose logic input, interfacing directly with the Status Register, is provided. This may be used as an auxiliary

method of routing digital information to the

µC via C-BUS. Output frequencies are produced from data loaded to the

MX803A. A programmable, general purpose, on-chip timer sets the tone transmit periods. A Dual-Tone Multi-Frequency

(DTMF) output is obtained by combining the 2 independent output frequencies in the integral summing amplifier. This

process can also be used for level correction.

Tones produced by the MX803A can be used in the system as modulation calibration inputs and as “CUE” audio

indications to the operator. Received tones are measured and their frequency indicated to the

µC in the form of a

received data word. A poor quality or incoherent tone will indicate Notone.

4.2 DBS800 Systems

The Digitally-Integrated Baseband Subsystem (DBS800) is a family of low power ICs which provide a comprehensive

range of audio processing and signaling functions for use within LMR and other Radio Systems. Each DBS800 IC may

be used as part of a complete audio system, or each IC may operate as a stand alone. The system and ICs are

partitioned in such a way that radio designers can easily select the device or devices appropriate to their needs.

The DBS800 family consists of the following ICs:

4.2.1 MX802 DVSR Codec

This is a full-duplex CVSD speech encoder/decoder with the ability to store and retrieve data within attached DRAM

(Dynamic Random Access Memory) using an on-chip DRAM controller. The MX802 also provides on-chip input and

output audio filtering.

4.2.2 MX803A Audio Signaling Processor

This provides an inband tone signaling ability to LMR and other Radio Systems.