The MX929B is a low voltage CMOS device containing all of the baseband signal processing and Medium Access Control (MAC) protocol functions required for a high performance 4-level FSK Wireless Packet Data Modem. It interfaces with the modem host PC and the radio modulation/demodulation circuits to deliver reliable two-way transfer of the application data over a wireless link. The MX929B assembles application data received from the host PC, adds forward error correction (FEC) and error detection (CRC) information, and interleaves the result for burst-error protection. After automatically adding symbol and frame sync codewords, the data packet is converted into filtered 4-level analog signals for modulating the radio transmitter. In receive mode, the MX929B performs the reverse function using the analog signals from the receiver discriminator. After error correction and removal of the packet overhead, the recovered application data is supplied to the host PC. CRC detected residual uncorrected data errors will be flagged. Readout of the SNR value during receipt of a packet is also provided. The MX929B uses data block sizes and FEC/CRC Algorithms that are compatible with RD-LAP and RCR STD-47 over-air-standards. The device is programmable to operate at standard bit rates from a wide range of Xtal/clock frequencies. The MX929B may be used with a 3.0V to 5.5V power supply and is available in the following package styles: 24-pin SSOP (MX929BDS), 24-pin SOIC (MX929BDW), and 24-pin PDIP (MX929BP).