The CMX469A is a full-duplex pin-selectable 1200/2400/4800bps Minimum Shift Key (MSK) Modem for FM radio links. The mark and space frequencies are 1200/1800, 1200/2400, and 2400/4800Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero crossing point. The use of a common Xtal oscillator with a choice of two clock frequencies (1.008MHz or 4.032MHz) provides data-rate, transmit frequencies, and RX/TX synchronization. The transmitter and receiver operate entirely independently including individual section powersave functions. The CMX469A includes on-chip circuitry for Carrier Detect and RX Clock Recovery, both of which are made available at output pins. RX, TX and Carrier Detect circuits contain bandpass filters to provide high quality signals to their respective paths. The carrier detect time constant is set by an external capacitor, which may be selected to optimize performance in high-noise environments. High sensitivity and good bit-error-rate performance can be achieved even under adverse signal conditions. The CMX469A operates with a 3.0V to 5.5V supply and is available in the following packages: 24-pin TSSOP (CMX469AE2), 20-pin SOIC (CMX469AD3), and 22-pin PDIP (CMX469AP6). 1999 MX-COM, Inc.