Digital Modulation SME
1038.6002.02 2.118 E-13
The following steps are required:
À Generation of a telegram
Set all ReFLEX25 parameters to the desired values. Make sure that REFLEX25:STATE:AUTO
is set to ON. Switch ReFLEX25 on and off again in order to generate a ReFLEX25 telegram in
the SME memory. This step is not required for custom frames.
À Reading out of the telegram data
You can now transfer any parts of the just generated telegram via IEC bus or the serial interface to
a host processor. Enter values from the above table for “start“ and “length“ in order to
determine the fragment you wish to read out. Use the following command sequence:
FORMAT PACKED Data output is performed in binary format
SOUR:DM:DATA:SEL “XMEM“ Determine memory extension as source
SOUR:DM:DATA:XMEM:MODE ALL Read out x and y bits
SOUR:DM:DATA:XMEM:START start Specify the start address of the data to be read
SOUR:DM:DATA:XMEM:LENGTH length Specify the length of the data to be read
SOUR:DM:DATA:DATA? Read out the x bits
SOUR:DM:DATA:ATT? Read out the y bits (only required for four-valued modulations
The setting commands in this step (except for the two last ones) are also necessary if you wish
to transfer custom frames to the SME without reading out data before.
À Modifying the telegram data
Each data byte received contains 8 valid x or y bits. The MSB of each byte belongs to the
symbol output
first
, the LSB to that output
last
(see also “Using custom frames CUS1...CUS9).
These data can now be manipulated using an appropriate PC program.
À Returning the telegram data
If the settings made during readout have not been changed, the data can simply be returned to
the SME using
SOUR:DM:DATA:DATA <x bits binary data>
SOUR:DM:DATA:ATT <y bits binary data>
When transferring several fragments, “start“ and “length“ are to be set before.
À Starting ReFLEX25
Set SOUR:REFL:STAT:AUTO OFF in order to avoid recalculation of the telegram when
ReFLEX is started. Then start ReFLEX25.
- Digital data at output connectors
In addition to the modulated RF, the digital data and the clock can also be tapped at the output
connectors. For the 2-valued modulations (1600bps/2FSK and 3200bps/2FSK), the data appear at
the DATA connector. For the four-valued modulations (3200bps/4FSK and 6400bps/4FSK), the x
bit of each symbol is output at the DATA connector, the associated y bit at the BURST connector.
When using the internal clock (setting CLOCK SOURCE INT in the menu), the symbol clock is
output at the CLOCK connector. Caution: Depending on bit rate and type of modulation, a 3200-
Hz clock is always output here!
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