COMMUNICATION SEMICONDUCTORS
MX805A
Sub-Audio Signaling
Processor
DATA BULLETIN
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
RX LPF
RX SUB-AUDIO
IN
180Hz/260Hz
•
•
•
•
Selectable Sub-Audio bandstop filter
NoTone (CTCSS RX) period timer
Low Power Operation
Member of DBS800 Family (C-BUS
Compatible)
RX SUB-AUDIO
OUT
COMPARATOR
IN
+
_
OUT
DIGITAL
NOISE
FILTER
FREQUENCY
ASSESMENT
NOTONE
TIMER
NOTONE
COMPARATOR
AMP
RAW NRZ DATA
NRZ RX
DATA AND
BAUD RATE
EXTRACTOR
AMP OUT
+
COMMAND DATA
REPLY DATA
FREQUENCY
MEASUREMENT
C-BUS
INTERFACE
AND
CONTROL
LOGIC
AMP IN
_
CHIP SELECT
INTERRUPT
SERIAL CLOCK
WAKE
ADDRESS SELECT
RX AMP
V
DD
V
BIAS
XTAL/
CLOCK
CLOCK
GENERATOR
XTAL
NRZ
RX DATA
RX
TX
NRZ RX
BAUD RATE
DATA BUFFER
AND
SHIFT REGISTER
NRZ
TX DATA
VARIABLE
BANDWIDTH
CTCSS SUB-
AUDIO FREQUENCY
SUB-AUDIO BANDSTOP
V
SS
AUDIO IN
AUDIO SIGNAL PATH
TX LEVEL
ADJUST
TX SUB-AUDIO LPF
TX SUB-AUDIO
OUT
AUDIO OUT
AUDIO BYPASS
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-
TM
Return-to Zero (NRZ) data reception and transmission to provide Digitally Coded Squelch (DCS/DPL ) and
TM
LTR 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).
ã
2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
All trademarks and service marks are held by their respective companies.
Doc. # 20480116.005
ETC [ ETC ]
