Marine AIS SART Processor
CMX7045
6
General Description
6.1 Overview
Tx Modem Functions
AIS 25kHz channel (GMSK, 9600bps, 2.4kHz deviation, BT = 0.4)
AIS Burst mode with full AIS frame formatting (HDLC-type)
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Bit stuffing
NRZI coding
Training sequence and start/stop flag insertion
CRC generation
AIS Raw mode (for greater flexibility)
Supports arbitrary data streams for user-defined protocols
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160-byte (equivalent to 5 AIS slots) Tx Data Buffer
Flexible Tx Interface
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Two-point modulation outputs, with independent gain and polarity controls
Analogue I/O Functions
Auxiliary ADC system
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A two-input 10-bit successive approximation ADC with integrated sample and hold
AuxADC1-2
Auxiliary DAC system
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Four general purpose auxiliary 10-bit DACs, AuxDAC1-4
Ramping auxiliary DAC, RAMDAC (using AuxDAC1)
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RAMDAC steps through a user-configured sequence of DAC output values to develop a
specific rising/falling output signal. This is useful for ramping an RF PA, and can be
configured to operate automatically at the start and end of a burst.
System Functions
All internal subsystems are controlled via a single serial host interface to reduce host µC pin count
and simplify external host driver complexity.
Transaction oriented command/response logical host interface executes tasks supporting normal
operation, device configuration, and functions to assist manufacturing calibration trimming of
external circuits.
Internal system clock derived from reference oscillator and eliminates the need for additional
XTAL or baseband clock oscillator.
System Clock Synthesisers generate two clocks for external use to support peripheral devices.
Function Image™ is loaded directly from the host µC via C-BUS.
Integrated 2.5V regulator can develop 2.5V from required 3.3V supply.
Powersave facilities minimise total system power.
6.2 AIS System Formats
The AIS system uses two basic channel access mechanisms: Self Organising Time Division Multiple
Access (SOTDMA) and Carrier-Sensing Time Division Multiple Access (CSTDMA). The CMX7045 is
compatible with both systems and offers additional features which simplify the implementation of an AIS
SART device conforming to IEC 61097-14.
The relevant International standards are:
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[1]
[2]
[3]
[4]
[5]
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ITU-R M.1371-4
IEC 61993-2 Class A
IEC 62287-1 Class B CSTDMA
IEC 62287-2 Class B SOTDMA
IEC 62320-1 Base Station
IEC 62320-2 Aids to Navigation
IEC 61097-14 AIS-SART
2013 CML Microsystems Plc
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D/7045FI-1.x/4
CMLMICRO [ CML MICROCIRCUITS ]
