CMX624 데이터 시트보기 (PDF) - MX-COM Inc
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CMX624 Datasheet PDF : 25 Pages
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Bell 202 and V.23 Compatible Modem
8
CMX624 Preliminary Information
4.3 Xtal Oscillator
The frequency and timing accuracy of the CMX624 is determined by a 3.579545MHz clock signal input to the
XTAL/CLOCK pin. This may be generated by the on-chip oscillator inverter using the external components
C1, C2 and X1 or may be supplied from an external source to the XTAL/CLOCK input. See Figure 2. If the
clock is supplied from an external source, components C1, C2, and X1 should not be fitted.
The on-chip oscillator is disabled in the 'Zero-Power' mode.
If the clock is provided by an external source, which may not always be running, then the 'Zero-Power' mode
must be enabled when the clock is not available. Failure to observe this rule may cause an increase in the
supply current consumption by the CMX624.
4.4 Rx Input Amplifier
The Rx Input Amplifier, with suitable external components, is used to adjust the received signal to the correct
amplitude for the FSK receiver and Energy Detect circuits and may also form part of a 2-wire or 4-wire hybrid
circuit. See Section 5.1.
4.5 Receive Filter
This block includes a bandpass filter whose characteristics are set by Bits 4 and 5 of the FSK MODE Register
according to the receive operating mode (Call Progress, 75/150bps FSK or 1200bps FSK). It is used to
attenuate out of band noise and interfering signals; especially the locally generated transmit FSK signal that
could otherwise interfere with the received FSK signal when the modem is operating in 2-wire duplex mode.
4.6 Equalizer
When receiving 1200bps FSK data an optional equalizer section can be enabled by setting Bit 6 of the FSK
MODE Register, compensates for one-half of the ETS Test Line 1 characteristics shown in Figure 6.
5
4
3
dB
ms
2
dB wrt 800Hz
ms wrt 1700Hz
1
0
0
500 1000 1500 2000 2500 3000 3500
Hz
Figure 6: ETS 300 114 Test Line 1 Characteristics (Normalized)
4000
©1999 MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480180.108
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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