CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX881
Baseband Processor for
PMR and Trunked Radios
D/881/2 May 2002
Advance Information
Full-Feature Audio-Processing, Signalling and Data for
Half Duplex Dual-Mode Analogue PMR and Trunked Radios
Features
• Automatic signal 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
• DTMF transmitter
• Programmable Selcall codec
• Half duplex FFSK/MSK modem, 1200/2400 b/s
with CRC and parity generator/checker
1.1 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.
The combination of CTCSS and DCS functions and Selcall operation of this product offer, under software
control, increased functionality, versatility and privacy.
To cater for call setup and system signalling the CMX881 offers an embedded 1200/2400 b/s MSK/FFSK
freeformat modem with checksum generation and reception and sync detection in the Rx path.
With ultra low power requirements and graduated powersave, this product only requires a smaller, lower-
power µC than existing PMR or trunked radio solutions, is available in compact SSOP and TSSOP
packages.
© 2002 CML Microsystems Plc