Brief Description

CMX882, a full-function half-duplex audio and signalling processor IC for FRS and PMR446 type facilities

suitable for both complex and simple end-designs. Under the control of the host µC, all voiceband requirements are catered for: voiceband and sub-audio filtering, pre/de-emphasis, compression and expansion and audio routing and global level setting with single or two-point modulation in the transmit path.

Features

•  Automatic signal type scanning and IRQ on detection of valid Rx signals, level or RSSI

•  Tone generator for caller recognition tunes

•  Programmable power down control

•  Programmable signal detection thresholds

•  Low Power operation with Zero Power mode

•  Uncommitted Aux ADC with switchable input to monitor signals

•  Silent operation by removal of unwanted calls

•  Selectable voice companding

•  XTCSS channel and data signalling

•  Robust automatic packet data protocol with: Error correction and detection, Interleaving and data scrambling/privacy coding.

•  Voice processing facilities, including Tx and Rx gain setting and voice/subaudio filtering

•  C-BUS serial host interface

•  RF interface allowing 1 or 2 point modulation

•  Programmable soft limiter

•  Enhanced CTCSS and 23/24 bit DCS codecs

•  Zero ‘talk down’ CTCSS decoder performance prevents dropouts

•  ‘All call code’ and ‘monitor’ modes for CTCSS

•  Audio scrambling

•  Robust Half Duplex FFSK/MSK modem, 1200/2400 bps, gets data through when signal is too degraded for voice – for text messaging/paging, location transfer, etc. applications.