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.