326 Keysight Signal Generators Programming Guide
Creating and Downloading User–Data Files
User File Data (Bit/Binary) Downloads (E4438C and E8267D)
Even though the signal generator views the downloaded data on a bit basis, it groups the data into
bytes, and when the designated number of bits is not a multiple of 8 bits, the last byte into one or
more 4–bit nibbles. To make the last nibble, the signal generator adds bits with a value of zero. The
signal generator does not show the added bits in the bit editor and ignores the added bits when it
modulates the data onto the signal, but these added bits do appear in the hex value displayed in the
bit file editor. The following example, which uses the same three bytes of data, further demonstrates
how the signal generator displays the data when only two bits of the last byte are part of the bits of
interest.
Notice that the bit file editor shows only two bytes and one nibble. In addition, the signal generator
shows the nibble as hex value 4 instead of 7 (78 is byte 3—ASCII character x in the SCPI command
line). This is because the signal generator sees bits 17 and 18, and assumes bits 19 and 20 are 00. As
viewed by the signal generator, this makes the nibble 0100. Even though the signal generator
extrapolates bits 19 and 20 to complete the nibble, it ignores these bits along with bits 21 through
24. As seen with the hex editor program, the signal generator does not actually change the three
bytes of data in the downloaded file.
For information on editing a file after downloading, see “Modifying User File Data” on page 338.
Hex value changes to 5A264
Designated bits
:MEM:DATA:BIT "3byte",18,#13Z&x
SCPI command to download the data
As Seen in the Signal Generator’s Bit File Editor
3 bytes of data
10 byte file header
(added by signal generator)
Designated number of bits (hex value = 18 decimal)
As Seen in a Hex Editor
0 1 0 1 1 0 1 0 0 0 1 0 0 1 1 0 0 1 1 1 1 0 0 0
Downloaded Data:
Byte 1
Byte 2
Byte 3
LSB
Designated 18 bits
5A
26
78
Hex Value:
MSB
0 1 0 1 1 0 1 0 0 0 1 0 0 1 1 0 0 1 0 0
Byte 1
Byte 2
Nibble
Designated number of bits
5A
26
4
Added bits
as seen in
the hex value
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