Keysight Technologies X-Series, Руководство по программированию

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332 Keysight CXG, EXG, and MXG X-Series Signal Generators Programming Guide
Creating and Downloading User–Data Files
User File Data (Bit/Binary) Downloads
Framed Binary Data
When using framed data, ensure that you use an even number of bytes and
that the bytes contain enough bits to fill the data fields within a timeslot or
frame. When there are not enough bits to fill a single timeslot or frame, the
signal generator replicates the data pattern until it fills the timeslot/frame.
The signal generator creates successive timeslots/frames when the user file
contains more bits than what it takes to fill a single timeslot or frame. When
there are not enough bits to completely fill successive timeslots or frames, the
signal generator truncates the data at the bit location where there is not
enough bits remaining and repeats the data pattern. This results in a data
pattern discontinuity. For example, a frame structure that uses 348 data bits
requires a minimum file size of 44 bytes (352 bits), but uses only 43.5 bytes
(348 bits). In this situation, the signal generator truncates the data from bit 3 to
bit 0 (bits in the last byte). Remember that the signal generator views the data
from MSB to LSB. For this example to have an even number of bytes and
enough bits to fill the data fields, the file needs 87 bytes (696 bits). This is
enough data to fill two frames while maintaining the integrity of the data
pattern, as illustrated in the following figure.
For information on editing a file after downloading, see “Modifying User File
Data” on page 341 .
User File Size
For Custom, when the signal generator creates the signal, it loads the data
from non–volatile memory into volatile memory, which is also the same
memory that the signal generator uses for Arb–based waveforms. For user
data files, volatile memory is commonly referred to as pattern ram memory
(PRAM). Because Custom user files use volatile memory, their maximum file
size depends on the baseband generator (BBG) option and the amount of
available PRAM (volatile memory that resides on the BBG). Table 6-6 shows
the maximum user file size for each baseband generator memory option.
348 data bits Ctrl
Ctrl
110100110110...01101111
352 bits (44 bytes):
Truncated data (bits 0–3)
not enough bits remaining to fill the next frame
348 data bits Ctrl
Ctrl 348 data bits Ctrl
Ctrl
011101100110110101110100110110...01101111
696 bits (87 bytes):
348 data bits
Ctrl
Ctrl
Frame 1 Frame 2
Frame 1 data repeated
Frame 1
Frame 2
Even Number of Bytes
Uneven Number of Bytes
(some data truncated)
(all bits used)
Data fills both frames (348 bits per frame) with no truncated bits
Frame 1 data
Framed Data
MSB
LSB