CMX909B
GMSK
Packet Data Modem
D/909B/1 August 2000
Advance Information
1.0
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Features
GMSK Modulation/Demodulation
Rx or Tx up to 38.4kbits/sec
Full and Short Data Packet Framing
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On-chip Packet Detection
Parallel Host Processor Interface
Low Power 3.0V/5.0V Operation
Flexible Operating and Powersave
Modes
Mobitex Compatible including R14N
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Short Block Frames
1.1
Brief Description
The CMX909B is a half-duplex Gaussian Minimum Shift Keyed (GMSK) BT=0.3 modem data pump with on-
chip packet data handling. GMSK modulation optimises the data throughput for a given bandwidth RF
channel and the on-chip packet data handling relieves the host µC of regular processing tasks, such as
maintaining Bit and Frame Synchronisation, Block Formatting, CRC and FEC Error Processing, Data
Interleaving and Scrambling. The demodulator uses decision feedback equalisation techniques to reduce the
channel distortion effects and enhance the receiver performance without the computational overhead of
maximum likelihood (Viterbi) estimation methods.
The CMX909B is pin, function and software backwards compatible with the FX909A and MX909A modems
and also uses the same external components. It offers improved performance, higher data rates and lower
voltage operation, as well as handling the recent R14N extension to Mobitex for short block frames. The
CMX909B also offers 2-strength Xtal driver circuitry – for wider choice of xtals, optional zero-error or one-error
frame sync. detection, multiple powersave options – for intelligent power management, and availability in both
24-pin TSSOP and SSOP low-height package options.
The CMX909B is ideally suited to wireless data applications such as Mobitex terminals, wireless telemetry,
licence-free radio data and ISM band radio schemes.
©
2001 Consumer Microcircuits Limited
CMLMICRO [ CML MICROCIRCUITS ]
