The CMX969 is a CMOS integrated circuit that contains all of the baseband signal processing and Medium Access Control (MAC) protocol functions required for a high performance DataTAC dual mode (RD-LAP 19200 bps and MDC 4800 bps) FSK Wireless Packet Data Modem suitable for use with the Motient/ARDIS network. It interfaces with the modem host processor and the radio modulation/demodulation circuits to deliver reliable two-way transfer of the application data over the wireless link. The CMX969 assembles application data received from the host processor, adds forward error correction (FEC) and error detection (CRC) information and interleaves the result for burst-error protection. After adding symbol and frame synchronisation codewords and channel status symbols, it converts the packet into a filtered analogue baseband signal for modulating the radio transmitter. In receive mode, the CMX969 performs the reverse function using the analogue baseband signals from the receiver frequency discriminator. After error correction and removal of the packet overhead, the recovered application data is supplied to the host processor. Any residual uncorrected errors in the data will be flagged. A readout of the received signal quality is also provided. An optional Autonomous Frame Sync Detection function is provided for use in Motient/ARDIS systems employing Single Frequency Re-use operation. The CMX969 uses signal filtering, data block formats and FEC/CRC algorithms compatible with the MDC and RD-LAP over-air standards. The device is programmable to operate from a wide choice of Xtal frequencies and is available in 24 pin DIP, SSOP and TSSOP packages.