MX805A Просмотр технического описания (PDF) - MX-COM Inc
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MX805A Datasheet PDF : 24 Pages
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Sub-Audio Signaling Processor
9
FROM RX
DISCRIMINATOR
MX805A RX LPF
Gain = 6dB
MX805A
MX805A
RX AMP
14
+
RX AMP IN
13
_
C9
R9
16
15
17
EXTERNAL
+ OP-AMP
_
270k
100k
NOTE 6
(see p.4)
D2
D1
15 mF
MX805A
R3
COMPARATOR
20
+
COMPARATOR IN
19
_
21
COMPARATOR
OUT
R10
R11
VDD
LEVEL SHIFT AND AMPLIFY
D.C. RESTORATION
Figure 4: MX805A Input Components using and External Op-Amp
4 General Description
4.1 Glossary
DCS
CTCSS
DPLTM
LTRTM
NRZ
fCO
fCTCSS IN
fCTCSS OUT
fTONE
fXTAL
RNRZRX
RNRZTX
sINPUT
Continuous Digitally Coded Squelch
Continuous Tone Controlled Sub-Audio Squelch
Digital Private Line
Logic Trunked Radio
Non-Return-to-Zero
Filter Cutoff frequency
Sub-Audio Rx frequency
Sub-Audio Tx frequency
Tone frequency
Xtal/Clock frequency
NRZ RX baud rate
NRZ TX baud rate
Audio input signal.
4.2 Operating Modes
4.2.1 NRZ Encoding
The NRZ Encoder is formed by a shift register and the TX Sub-Audio Lowpass Filter. Data loaded from the
Command Data line is output one 8-bit byte at a time from the NRZ Tx Data Register. The output data level
may be adjusted and filtered. Data may be pre-emphasized via a C-BUS command. The expected Rx baud
rate is programmed as the NRZ Tx Baud Rate (RNRZTX). See Table 8
4.2.2 CTCSS Encoding
The CTCSS Tone Encoder is comprised of a clock divider programmed by an 11-bit binary number (Q)
loaded to the CTCSS Tx Frequency Register (See Table 8) via the C-BUS Command Data line.
The square-wave output of the encoder is fed through the Tx Level Adjust variable gain block to the Tx
Sub-Audio lowpass filter, a variable gain bandwidth circuit controlled by 4-bits (P) if the CTCSS Tx Frequency
Register. The Tx Sub-Audio output is a sine-wave. Standard and nonstandard sub-audio tones are available.
A CDCS turnoff tone may also be generated.
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
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