CMX7163 QAM Modem
CMX7163
read Receive FIFO Data
Byte register
Oldest Rx FIFO data byte is removed from FIFO and returned, Rx FIFO Word
updated
read Receive FIFO Data
Word register
Oldest Rx FIFO data word (control and data bytes) is removed from FIFO and
returned, Rx FIFO control word updated
C-BUS
interface
CMD
Level
Rx Level
CMD FIFO LEVEL
RX FIFO LEVEL
RX FIFO CTRL
CMD FIFO CTRL
CMD FIFO
WRITE16
RX FIFO
READ16
CMD FIFO
WRITE8
RX FIFO
READ8
mux
mux
LSB
MSB
LSB
MSB
CMD
Level
128x16 CMD FIFO
128x16 RX FIFO
Rx Level
Figure 25 Command and Rx Data FIFOs
Raw or formatted data may be transmitted with the CMX7163 adding preamble, frame sync and tail bits.
Raw or formatted transmission/reception is selected using the Modem Mode and Control - $6B write
register, each whole transmission/reception must continue in the selected mode. Relevant registers are:
10.1.18 Modem Mode and Control - $6B 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
10.1.4 FIFO Control - $50 write.
Note: The Command FIFO and Command Buffer will automatically be flushed when a carrier sense
attempt to transmit results in the CMX7163 reverting to receive mode. This is to avoid accidentally
processing transmit commands pre-loaded by the host as receive commands. This is the only situation in
which the FIFOs or buffers will be flushed other than by direct host instruction.
7.4.14 Data Buffering
To expand the buffering capabilities of the CMX7163 two internal buffers are provided:
A Command buffer which buffers commands from the control FIFO which are yet to be processed.
An Rx data buffer which buffers received data yet to be loaded into the Rx data FIFO.
Transfer between the FIFOs and their respective buffers will occur during transmission, reception and Idle
mode. Such transfer is not instantaneous so the FIFO fill levels should be used to indicate how much data
the host may read or write at any time.
The Internal Buffer Fill Level - $70 read register allows the buffer fill levels to be read; their contents will be
flushed when the respective FIFO is flushed.
2014 CML Microsystems Plc
Page 41
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