MX828 查看數據表（PDF） - MX-COM Inc
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MX828 Datasheet PDF : 34 Pages
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CTCSS/DCS/SelCall Processor
6
MX828 PRELIMINARY INFORMATION
External Components Notes:
1. R2, R6, R7 and C3 form the gain components for the Summing Amplifier. R6 and R7 should be chosen as
required from the system specification, using the following formula:
Tx Sub Audio Gain = − R2
R6
Tx Audio Gain = − R2
R7
2. R3, R4, C5 and C7 form the gain components for the Rx Input Amplifier. R4 should be chosen as required by the
signal level, using the following formula:
Gain
=
R3
−
R4
C7 x R4 should be chosen so as not to compromise the low frequency performance of this product.
3. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at least 40% of
VDD, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain crystal oscillator design
assistance, consult your crystal manufacturer.
4. General Description
The MX828 is a signaling encoder/decoder for use in land mobile radio equipment, see Figure 1. The transmitter section
of the MX828 has independently controllable tone generators for sub-audio (CTCSS) and inband (SelCall) signaling. Also
featured is a DCS code generator, which may be used in place of the CTCSS tone generator.
The receiver section of the MX828 has a fast/predictive CTCSS tone detector which operates in parallel with a DCS
decoder and a CTCSS/SelCall tone decoder. The latter is switchable to perform either CTCSS or SelCall tone decoding of
a user-programmable set of up to 15 tones. In the CTCSS mode it performs a more accurate (but slower) analysis of the
tones detected by the fast/predictive CTCSS tone detector, which is a single detector that is switchable to provide either a
fast response to any CTCSS tone (FAST DETECT mode) or a fast response to a single user-programmed CTCSS tone
(PREDICTIVE mode).
Both the DCS transmit and receive bit rates are fixed at 134.4bps.
Other functions on the MX828 are a comparator with programmable threshold level, a general purpose timer and a
summing amplifier with two adjustable gain blocks, which may be used for two point modulation, for example. All MX828
functions are controlled by an external µC over the “C-BUS” interface, a serial interface designed to reduce interference
levels in radio equipment.
© 1997 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 336 744-5050 Fax: 336 744-5054
Doc. # 20480161.002
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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