CMX469A
CML Microcircuits
1200/2400/4800 Baud
FFSK/MSK Modem
COMMUNICA
TION SEMICONDUCTORS
D/469A/3 June 2009
Features
Applications
• Full-Duplex FFSK/MSK Modem with
Separate Rx and Tx Enable Functions
• Pin Selectable Data Rates:
1200, 2400 or 4800 Baud
• Pin Selectable Xtal/Clock Inputs:
1.008MHz or 4.032MHz
• Clock Recovery Facility
• Carrier Detect Facility
• Low Power Operation (2.0mA typ. at 3.0V)
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1.1
Data-Over Radio
Personal/Cordless Telephone
Radio and General Applications
Narrowband Coax Data Channels
Two Way Radio (MPT1327) Signalling
Portable Data Terminals
Brief Description
The CMX469A is a single-chip CMOS LSI circuit which operates as a full-duplex 1200, 2400 or
4800 baud FFSK/MSK modem. The mark and space frequencies are 1200/1800, 1200/2400 and
2400/4800 Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero
crossing point. A common Xtal oscillator with a choice of two clock frequencies (1.008MHz or
4.032MHz) provides baud-rate, transmit frequencies, and Rx and Tx synchronization.
The transmitter and receiver operate entirely independently, including the individual section
powersave functions. The CMX469A includes on-chip circuitry for Carrier Detect and Rx Clock
recovery, both of which are made available as output pins. Rx, Tx and Carrier Detect paths
contain bandpass filters to optimise signal conditions in each section of the modem. The
CMX469A demonstrates good sensitivity and bit-error-rate under adverse signal conditions. The
Carrier Detect time constant is set by an external capacitor, so that the product's performance can
be optimised in high noise environments. This low-power device operates from a single supply
between 2.7V and 5.5V, requires few external components and is available in a wide variety of
plastic packages.
© 2009 CML Microsystems Plc
