User`s guide

Chapter 7 115
Reading/Writing Measurement Data
Entering Data into a Trace
7. Reading/Writing Measurement Data
Entering Data into a Trace
You can change the data/memory trace on the LCD by writing the new data into the
“Formatted data array” on page 109/“Formatted memory arrays” on page 110.
When you write data into formatted data/memory array, you can choose either the ASCII
or binary transfer format (see “Data Transfer Format” on page 104).
Example 7-3 and Example 7-4 show sample programs that demonstrate how to write data
into formatted data arrays. The sample program in Example 7-3 uses the ASCII transfer
format while the sample in Example 7-4 uses the binary transfer format. You can find the
source files of these programs, named write_a.htb and write_b.htb, on the sample program
disk.
Each of the sample programs holds the sweep on channel 1, retrieves the data from a
specified file (a file saved measurement data using the :MMEM:STOR:FDAT command
on page 356 command), and populates trace 1 for channel 1 with the retrieved data.
The program in Example 7-3 is described in detail below:
Line 50 Assigns a GPIB address to the I/O pass.
Line 70 Passes control to a subprogram named Inp_file_name, which lets the
user input a file name, and then stores the returned file name into the
File$ variable. For more information on the Inp_file_name
subprogram, refer to the description in Example 7-4.
Lines 90 to 110 These lines set channel 1's active trace to trace 1 and hold the sweep.
Lines 130 to 140 These lines retrieve the number of points in channel 1 and stores that
number into the Nop variable.
Line 150 Resizes the Fdata array based on the value of the Nop variable (the
number of points).
Line 170 This line points to the statement block to be executed if an error occurs
in retrieving data from the file (for example, if no file matches File$).
Lines 180 to 260 These lines retrieve the formatted data from the file identified by
File$, and store the data into the Fdata array.
Line 280 Sets the data transfer format to ASCII.
Line 300 Writes Fdata into the formatted data array for the active trace (trace 1)
in channel 1.
Lines 340 to 380 This statement block is executed if an error occurs in retrieving data
from the file.