CMX7163 QAM Modem
CMX7163
7.4 Device Control
Once the Function Image™ is loaded the CMX7163 can be set into one of four main modes using the
Modem Mode and Control - $6B write register:
Idle mode – for configuration or low power operation
Transmit mode – for transmission of raw or formatted data
Receive mode – for detection and reception of bursts containing raw or formatted data
Carrier sense mode – for attempting to transmit if the channel is free, otherwise continuing to
receive
These four modes are described in the following sections. All control is carried out over the C-BUS
interface: either directly to operational registers in transmit, receive and carrier sense modes or, for
parameters that are not likely to change during operation, using the Programming Register - $6A write in
Idle mode.
To conserve power when the device is not actively processing a signal, place the device into Idle mode.
Additional power-saving can be achieved by disabling unused hardware blocks, however, most of the
hardware power-saving is automatic. Note that V
must be enabled to allow any of the Input or Output
BIAS
blocks to function. It is only possible to write to the Programming register whilst in Idle mode. See:
10.1.17 Programming Register - $6A write
10.1.18 Modem Mode and Control - $6B write
10.2 Programming Register Operation
10.1.24 VBIAS Control - $B7 write.
7.4.1 Normal Operation Overview
In normal operation (after the CMX7163 is configured) the appropriate mode must be selected and data
provided in transmit or retrieved in receive. This process is carried out by selecting the mode (Tx, Rx or
Carrier Sense), selecting the frame sync to use (Frame Sync 1 or 2) and selecting formatted or raw data.
Such a selection is required at the beginning of transmission or reception of a burst.
In transmit (or following a carrier sense period where no signal is detected on channel) the CMX7163 will
begin by switching GPIO signals as configured by the transmit sequence. The RAMDAC can also be
configured to ramp up at this point. Transmission then begins with preamble and the selected frame sync.
The main payload of user data comes next, ending with selectable tail bits. The burst ends with the
transmission sequence ramping the RAMDAC down and/or switching GPIO signals.
In receive (or following a carrier sense period where signal is detected on channel) the CMX7163 will begin
by searching for either or both of the configured frame sync patterns. On detection of a frame sync,
reception and delivery of Rx data will begin. Reception continues until the CMX7163 is switched into a
different mode, determined by the host.
During the burst, data must be transferred into or out of the CMX7163. Transfers use the Command FIFO
to transfer data and commands about data type into the CMX7163, and the Rx FIFO to transfer data out of
the CMX7163. The IRQ Status register is used to indicate that the data has been dealt with. The CMX7163
can be configured to interrupt the host when a specified data block has been transferred, or on FIFO fill
level.
The CMX7163 offers internal buffering of data in addition to the Command and Rx FIFOs in both receive
and transmit directions. The amount of buffering offered is dependant on the mode in which the device is
operating. In the process of burst transmission or reception the most significant registers are:
10.1.18 Modem Mode and Control - $6B write
10.1.37 IRQ Status - $7E read
10.1.19 IRQ Mask - $6C write
10.1.3 Modem Command FIFO Data/Control - $48, $49 and $4A write
10.1.26 Receive FIFO Data/Control - $4C, $4D, $4E read
10.1.25 Modem Command FIFO Level - $4B read
10.1.27 Receive FIFO Level - $4F read.
2014 CML Microsystems Plc
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