AIS Baseband IC with/without RF Synthesiser
CMX7032/CMX7042
7.4 System Description and Tasks
This section describes the operation of main sections of the CMX7032/CMX7042 and the task-oriented
logical interface provided to the external host device.
7.4.1 Signal Routing
The CMX7032/CMX7042 provides processing capability for two simultaneous receive channels (either two
AIS or one AIS and one DSC) or one Tx channel (AIS).
The inputs to the two receiver channels are nominally allocated to the RX1N and RX2N pins of the device,
however they can be re-allocated by the user by use of the Input Signal Routing C-BUS register, $B1. The
SpareN pin can also be used as an input to the receivers if required. By default the device will route RX1N
to Rx channel 1 and RX2N to Rx channel 2, which leaves the SpareN signal available to the ADC. All of
these inputs are configured around an inverting op-amp stage to facilitate gain and filtering adjustments. In
addition, the Rx channel inputs are equipped with programmable gain stages for further level adjustments
as required.
The Tx Modulation output signals may be configured to be suitable for two-point modulation circuits or
alternatively an I/Q upconverter. Signal levels on both output pins, MOD1 and MOD2, can be set to within
0.2dB using a Configuration Mode task.
7.4.2 Operating Modes
The CMX7032/CMX7042 operates in either:
o
o
Configuration mode
Normal mode
Configuration mode is used to set up various operating parameters of the CMX7032/CMX7042
subsystems, e.g. Transmit format, timing parameters etc. following a power-up or reset. The modem
section is disabled when the device is in Configuration mode. Configuration mode uses dedicated tasks
that are not valid whilst in Normal mode.
Normal mode is used when actively running the CMX7032/CMX7042 modem and other subsystems.
Normal mode uses dedicated tasks that are not valid whilst in Configuration mode.
“Enter Config Mode” (ECM) is a Normal mode task that switches the device from Normal to Configuration
mode. “Exit Config Mode” (EXIT_CONFIG) is a Configuration mode task that switches the device from
Configuration to Normal mode.
7.4.3 Modem and Data Units
The CMX7032/CMX7042 is logically divided into two main units which can accept and perform tasks
separately:
o
o
Modem Unit
Data Unit
The Modem Unit is primarily responsible for processing Tx data from the internal Tx data buffer,
presenting it on the MOD1 and MOD2 pins, processing the Rx input signals to recover the Rx data they
represent and storing that data in the internal Rx data buffers.
The Data Unit is primarily responsible for transferring data between the internal data buffers or
subsystems and the C-BUS registers, from where they can be accessed by the host µC.
When the device is in Normal mode, the Command register, $C8, is a 16 bit C-BUS write register that
contains task fields for both Data and Modem units. A task is invoked by writing its code into the Data
Task or Modem Task fields. A single C-BUS write transaction will change all Command register fields.
Often, the host will only want to issue either a Data or Modem task, in which case it should ensure that the
other task field is set to all zeroes, corresponding to a null/idle task. Sometimes it is useful to issue Data
and Modem tasks simultaneously, in which case, the Data task will always be completed before the
Modem task is started.
2012 CML Microsystems Plc
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D/7032/42_FI1.2/13
CMLMICRO [ CML MICROCIRCUITS ]
