Keysight CXG, EXG, and MXG X-Series Signal Generators Programming Guide 349
Creating and Downloading User–Data Files
Pattern RAM (PRAM) Data Downloads
PRAM File Size
Because volatile memory resides on the baseband generator (BBG), the
maximum PRAM file size depends on the installed baseband generator option.
After downloading, the signal generator translates each downloaded data bit
into a 32–bit word:
— 1 downloaded data bit
— 7 downloaded control bits as shown in
— 24 bits added by the signal generator
To properly size a PRAM file, you must determine the file size after the 32–bit
translation process. The signal generator measures a PRAM file size in units of
bytes; each 32–bit word equals 4 bytes.
Determining the File Size
The following example shows how to calculate a downloaded file size using a
PRAM file that contains 89 bytes (data bits plus 7 control bits per data bit):
89 bytes + [(89 x 24 bits) / 8] = 356 bytes
Because the file downloads one fourth of the translated 32–bit word, another
method to calculate the file size is to multiply the downloaded file size by four:
89 bytes x 4 = 356 bytes
“Signal Generator Memory” on page 321
and
.
Minimum File Size
A PRAM file requires a minimum of 60 bytes to create a signal. If the
downloaded file contains less than 60 bytes, the signal generator replicates the
file until the file size meets the 60 byte minimum. This replication process
occurs after you select the file and turn the modulation format on. The
following example shows this process using a downloaded 14–byte file:
— During the file download, the 14 bytes are translated into 56 bytes (fourteen
32–bit words).
14 bytes x 4 = 56 bytes
— After selecting and turning the format on, the signal generator replicates
the file contents to create the 60 byte minimum file size
File size increases
by a factor of 4
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