MX805A Просмотр технического описания (PDF) - MX-COM Inc

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MX805A

Sub-Audio Signaling Processor

MX-COM Inc  

DATA BULLETIN

MX805A

Sub-Audio Signaling

Processor

Features

 Non-predictive CTCSS Tone Decoder

 DCS Sub-Audio Signal demodulator

 CTCSS /NRZ Encoder with TX level

adjustment and lowpass filter output

stage with optional NRZ pre-emphasis

 Selectable Sub-Audio bandstop filter

 NoTone (CTCSS RX) period timer

 Low Power Operation

 Member of DBS800 Family (C-BUS

Compatible)

RX SUB-AUDIO

IN

RX LPF

AMP OUT

180Hz/260Hz

+

AMP IN

_

RX AMP

V

DD

V

BIAS

XTAL/

CLOCK

XTAL

V

SS

CLOCK

GENERATOR

RX SUB-AUDIO

OUT

COMPARATOR

IN

OUT

+

_

DIGITAL

NOISE

FILTER

COMPARATOR

AMP

RAW NRZ DATA

NRZ RX

DATA AND

BAUD RATE

EXTRACTOR

NRZ

RX DATA

NRZ RX

BAUD RATE

RX

TX

DATA BUFFER

AND

SHIFT REGISTER

NRZ

TX DATA

CTCSS SUB-

AUDIO FREQUENCY

SUB-AUDIO BANDSTOP

AUDIO IN

AUDIO SIGNAL PATH

FREQUENCY

ASSESMENT

FREQUENCY

MEASUREMENT

TX LEVEL

ADJUST

AUDIO BYPASS

NOTONE

TIMER

NOTONE

C-BUS

INTERFACE

AND

CONTROL

LOGIC

COMMAND DATA

REPLY DATA

CHIP SELECT

INTERRUPT

SERIAL CLOCK

WAKE

ADDRESS SELECT

VARIABLE

BANDWIDTH

TX SUB-AUDIO

OUT

TX SUB-AUDIO LPF

AUDIO OUT

The MX805A is a sub-audio frequency signaling processor that provides outband audio and digital signaling

capability for LMR systems. Designed for the transmission and non-predictive reception of Continuous Tone

Controlled Squelch (CTCSS) tones and other non-standard frequencies, the MX805A also handles Non-

Return-to Zero (NRZ) data reception and transmission to provide Digitally Coded Squelch (DCS/DPLTM) and

LTRTM signaling.

Setting the MX805A functions and modes is accomplished by data loaded from the microcontroller to the

controlling registers within the device. Reply Data and Interrupt protocol keep the microcontroller up to date

on the operational status of the circuitry. CTCSS tone data for transmission is generated in the

microcontroller, loaded to the CTCSS TX Frequency Register, encoded and output as a tone via the TX Sub-

audio LPF. Received non-predicted CTCSS tone frequencies are measured and the resulting data, in the

form of a 2-byte data word, is presented to the microcontroller for matching against a lookup table. Noise

filtering is provided to improve the signal quality prior to measurement. NRZ coded data streams for

transmission, when generated within a microcontroller, are loaded to the NRZ TX Data Buffer and output, in

8-bit bytes, through the lowpass filter circuitry as subaudible signals. DCS turnoff tones can be added to the

data signals by switching the MX805A to the CTCSS transmit mode at the appropriate time. NRZ coding is

produced by the microcontroller and translated to subaudio signals by the MX805A. Received NRZ data is

filtered, detected, and placed into the NRZ Data Register, which is then available for transfer (one byte at a

time) to the microcontroller for decoding by software. Clock extraction circuitry is provided on-chip. TX ad RX

baud rates are selectable.

Hardware and software are designed to allow consecutive addressing of two MX805A Sub-Audio Signaling

Processors to achieve multi-mode duplex operation. Powersaving may be controlled by software or by an

input dedicated to the purpose.

The MX805A may be used with a 5.0V power supply and is available in the following packages:

24-pin SOIC (MX805ADW), 24-pin PLCC (MX805ALH), and 24-pin PDIP (MX805AP).

1998 MX-COM, Inc.

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480116.004

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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