Brief Description
CMX881, a full-function half-duplex audio and signalling processor IC for both PMR and Trunked radio systems suitable for 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 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 powerdown control
• Programmable signal detection thresholds
• Low Power operation with ‘Zero Power’ mode
• Uncommitted Aux ADC with switchable input to monitor signals
• Meets ETS 300 086, MPT1327, PAA1382 and ETS 300 230 specifications
• 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 ‘Talkdown’ CTCSS decoder performance prevents dropouts
• DTMF transmitter
• Programmable Selcall codec
• Robust half-duplex FFSK/MSK modem, 1200/2400bps with CRC and parity generator/checker, gets data through when signal is too degraded for voice – for text messaging/paging, location transfer, etc. applications.