Digital PMR Radio Processor
CMX7131/CMX7141
5
General Description
5.1 Features
7131/7141FI-3.1 for the CMX7131/CMX7141 is intended for use in half duplex digital PMR equipment
using 4-FSK modulation at 4800 bps suitable for 6.25kHz channel systems.
Much of the NXDN standard air interface protocol is embedded within the CMX7131/CMX7141 operation
namely:
Air Interface Physical Layer 1
4-FSK modulation and demodulation
Bit and symbol definition
Frequency and symbol synchronisation
Transmission burst building and splitting
Air Interface – Data Link Layer 2
Channel coding (FEC, CRC)
Interleaving, de-interleaving and bit ordering
Frame building and synchronising
Burst and parameter definition
Interfacing of voice applications (voice data) with the Physical Layer
Data bearer services
Exchanging signalling and/or user data with the Call Control Layer
Automatic RAN detection
The 7131/7141FI-3.1 has two receiver interface modes: Limiter/Discriminator (LD) mode is selected by
default and is compatible with 7131/7141FI-3.0.x for conventional limiter/discriminator receivers; I/Q mode
is tailored for operation with the CMX994 Direct Conversion Receiver IC. The transmitter can provide a
conventional output suitable for 2-point modulation or for an I/Q interface.
A flexible power control facility allows the device to be placed in its optimum powersave mode when not
actively processing signals.
The device includes a crystal clock generator, with buffered output, to provide a common system clock if
required.
A block diagram of the device is shown in Figure 1.
The signal processing blocks can be routed from any of the three DISC/ALT/MIC input pins.
Other Functions Include:
Automatic Tx sequencer simplifies host control
RAMDAC operation
TxENA and RxENA hardware signals
Two-point or I/Q modulation outputs
Hard or Soft data options
2014 CML Microsystems Plc
Page 18
D/7141_FI-3.x/6
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