CMX7163 QAM Modem
CMX7163
7.4.2 Basic Tx and Rx Operation
The CMX7163 has many features that provide a great deal of flexibility, but basic data transmission and
reception can be carried out fairly easily by understanding the operation of just a few registers. There are
other ways of controlling signal transmission and reception but a basic example is given below:
Basic Transmit Operation
Transmission of raw data bytes uses the following procedure:
C-BUS Operation
Action
Description
Write $0080 to FIFO Control Flush the
To ensure that no data is remaining from
previous transmissions
Selects blocks of data bytes to be transmitted –
8 bytes in each, after which the CMX7163 will
request more data from the host
- $50 write
Write $18 to the Modem
Command FIFO
Select 8 byte data
Command FIFO Control Byte blocks
(see Modem Command
FIFO Data/Control - $48, $49
and $4A write)
Write 8 data bytes to the
Modem Command FIFO
Data Byte - see Modem
Command FIFO
Pre load the
Command FIFO
This provides a buffer of 8 data bytes before
transmission starts, so that the host does not
with data to transmit need to write data as promptly for the rest of the
burst
Data/Control - $48, $49 and
$4A write
Write $0042 to Modem Mode Start transmission
and Control - $6B write
Initiates a transmission with preamble, Frame
Sync 1 and then the pre loaded data
Poll the IRQ Status - $7E
read register for bit 8 –
Cmd Done = 1
Wait until the data
block has been
read from the FIFO
When this is complete a further 8 data bytes
may be written to the Modem Command FIFO
Data Byte (see Modem Command FIFO
Data/Control - $48, $49 and $4A write) and the
IRQ Status - $7E read register polled again. This
step may be repeated as many times as needed
Write $F000 to the Modem
Command FIFO Word (see
Modem Command FIFO
Data/Control - $48, $49 and
$4A write)
Indicate burst end is Indicate that no more data is to follow – so when
intended
the data loaded into the Command FIFO is
modulated the CMX7163 will terminate the burst
with tail bits
Poll the IRQ Status - $7E
read register for bit 9 – Tx
Last Tail = 1
Wait until the burst
ends
The burst has completed, with all data and tail
bits having been modulated. It is now possible to
transition to other modes, or transmit another
burst using the Modem Mode and Control - $6B
write register
The procedure described above can be adapted, making transmission of different numbers of bytes, bits
or coded blocks possible.
Basic Receive Operation
Reception of raw data bytes uses the following procedure:
C-BUS Operation
Write $8000 to FIFO
Control - $50 write
Write $1400 to the
Modem Command FIFO reception – repeat
Word (see Modem
Command FIFO
Action
Flush the Command
FIFO
Description
To ensure that no data is remaining from
previous data reception
Selects blocks of data bytes to be received (after
frame sync is detected) – 4 bytes in each, at
which point the host will be notified. This will
continue until the mode is changed
Select 4 byte data block
forever
Data/Control - $48, $49
and $4A write)
2014 CML Microsystems Plc
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