CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX883
Baseband Processor for
‘Leisure Radios’
D/883/2 May 2002
Advance Information
Full-Feature Audio-Processing and Signalling for
Half Duplex FRS, MURS, GMRS and PMR446 ‘Leisure’ Radios
Features
• Automatic signal 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
• 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
• All call code and monitor modes for CTCSS
• Selectable voice companding
• XTCSS channel and data signalling
1.1 Brief Description
CMX883, a full-function half-duplex audio and signalling processor IC for FRS and PMR446 type facilities
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.
The combination of new and standard signalling functions of this product offer, under software control,
increased functionality, versatility and privacy. Standard Extended-Code CTCSS and DCS are integrated
with the new XTCSS code implementation. XTCSS provides additional and improved squelch-centred
privacy codes with the added advantage of ‘silent operation’; no annoying interference from other sub-
audio users. XTCSS fitted radios enjoy more privacy and flexibility of operation.
With ultra low power requirements and graduated powersave, this product only requires a smaller, lower-
power µC than existing FRS/PMR446 solutions, is available in compact SSOP and TSSOP packages.
© 2002 CML Microsystems Plc