MX826 查看數據表（PDF） - MX-COM Inc

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MX826

AMPS/NAMPS SYSTEM AUDIO PROCESSOR

MX-COM Inc  

AMPS/NAMPS System Audio Processor.

Description

The MX826 is a µProcessor controlled full-duplex

audio processor on a single-chip with separate TX and

RX paths to provide all the filter/gain/limiting functions

necessary to pre-process audio, wideband-data and SAT

cellular communications systems using the AMPS/NAMPS

or TACS/ETACS/JTACS specifications.

Selectable inputs available to the transmit path are: a

choice of two microphones and DTMF/signaling, with

access, in this path, to external compression circuitry.

Operationally the TX path provides input gain/filtering, a

deviation limiter and TX Modulation Drive controls.

In the RX path the SAT signal is separated from the

incoming audio via a filter block and made available at a

separate pin for mixing externally with the TX Modulation

Drive.

The RX path consists of an input gain/filter block for

MX826 Preliminary Information

voice, inputs from an external audio expansion system

and an output gain control driving either a loudspeaker

system or earpiece.

Unique to the MX816/826/836 cellular audio

processors is the ability to route audio (TX or RX) to an

external Voice Store and Retrieve (VSR) device such as

the MX802 or MX812 thus providing the radio system with

a voice answering and announcement facility using

external DRAM.

As a member of the DBS800 family, the MX826

follows C-BUS protocol. (C-BUS is the serial interface

used by all DBS800 integrated circuits.)

The MX826, a low-power CMOS device which reduces

the amount of microcircuits and components required in

a cellular audio system by providing more functions on a

single chip, is available in 28-pin SOIC and CDIP packages.

Pin Function

1 Xtal: The output of the on-chip clock oscillator.

2 Xtal/Clock: The input to the on-chip clock oscillator. A Xtal or externally derived clock (fXTAL) should be

connected here. Note that operation of the MX826 without a suitable Xtal or clock input may cause device

damage. See Figure 2 (notes).

3 Serial Clock: The “C-BUS” serial data clock input. This clock, produced by the µController, is used for

transfer timing of commands and data to the MX826. See Timing Diagrams.

4 Command Data: The “C-BUS” serial data input from the µController. Data is loaded to the MX826 in 8-

bit bytes, MSB (B7) first, and LSB (B0) last, synchronized to the Serial Clock. See Timing Diagrams.

5 Chip Select (CS): The “C-BUS” data loading control function. This input is provided by the µController.

Data transfer sequences are initiated, completed or aborted by this signal. See Timing Diagrams.

6 VBIAS: The internal circuitry bias line, held at VDD/2 this pin must be decoupled to VSS. See Figure 2.

7 Rx Audio In: Normally taken from the radio's discriminator output, this input has a 1MΩ internal resistor

to VBIAS and requires to be connected via a capacitor.

8 Expand/Store: A common output that can be used as either an input to an external audio expander or

the input to a voice storage medium such as the MX812. Components relevant to the external device

requirements should be used at this output. See Figures 2 and 3.

9 (Expanded) Audio In: The audio input, via SW5, from an external expander or audio mixing function. This

input has a 1MΩ internal resistor to VBIAS and requires to be connected via a capacitor. See Figures 2 and

3.

10 TX Mod Out: The composite TX audio output to the transmitter modulator from a variable attenuation

stage (11H). This output is set to VBIAS via an internal 1MΩ resistor when set to Powersave or OFF.

11 LS Audio Out: An audio output of the Rx path (or selected audios, see Figure 3) for a loudspeaker system.

This is available for handsfree operation. This output can be connected to V when not required, by SW6

BIAS

(Configuration Command (10H)). A driver amplifier may be required.

Notes on Inputs:To minimize aliasing effects, lowpass filtering may be required at the inputs to this device

(especially those supplied from switched-capacitor-type devices) to ensure the input spectrum is kept

below 63kHz.

© 1997 MX•COM Inc.

www.mxcom.com Tele: 800 638-5577 910 744-5050 Fax: 910 744-5054

Doc. # 20480070.004

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

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