MX909A

COMMUNICATION SEMICONDUCTORS DATA BULLETIN MX909A GMSK Modem Data Pump PRELIMINARY INFORMATION GMSK Modulation RX or TX up to 19.2k bits/sec Full Data Packet Framing Mobitex¥ Compatible Flexible Operating Modes Host µC Interface Low Power 3.3V/5.0V Operation 24-Pin Small Form Package Option RADIO MODULATOR RF DISCRIMINATOR ANALOG TX ANALOG RX MX909A MODEM DATA PUMP DATA AND CONTROL BUS HOST µC SYSTEM APPLICATION PROCESSING The MX909A is a low power CMOS device containing all of the baseband signal processing and Medium Access Control (MAC) protocol functions required for a high performance GMSK Wireless Packet Data Modem. The MX909A interfaces with a host µC and radio modulation/demodulation circuits to deliver reliable two-way transfer of application data over a wireless link. The MX909A assembles application data received from the host µC, adds forward error correction (FEC), and error detection (CRC) codes, time-spreads this data by interleaving (burst-error protection) and scrambles (randomizes) the bit pattern. After automatically adding bit and frame sync codewords, the data packet is converted into analog GMSK signals for modulating into the radio transmitter. In the receive mode, the MX909A performs the reverse function using the analog signals from the receivers discriminator. After error correction and removal of the packet overhead, the recovered application data is supplied to the host µC. Any CRC detected residual uncorrected errors in t...