User`s guide

Chapter 7 117
Reading/Writing Measurement Data
Entering Data into a Trace
7. Reading/Writing Measurement Data
The program in Example 7-4 is described in detail below:
Lines 50 to 60 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.
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 binary.
Line 290 Creates the data header and stores it into the Header$ variable.
Line 300 Sends the command that writes data into the formatted data array for
the active trace (trace 1) in channel 1, following it with the data header
(Header$).
Line 310 Sends the data itself (Fdata), following it with a message terminator.
NOTE Because binary data must be written without being formatted, the program uses an I/O path
(@Binary) that is configured to support writing unformatted data.
Lines 340 to 380 This statement block is executed if an error occurs in retrieving data
from the file.
The Inp_file_name subprogram in lines 440 to 540, which is used to enter a save filename,
is described below.
Line 460 Allows the user to return to the entry start line and re-enter the data if
an error (such as an invalid entry) occurs while entering the target file
name.
Lines 480 to 490 These lines prompt the user to enter the target file name. The program
does not continue till the user actually enters the file name.
Lines 500 to 510 These lines display the entered file name and waits for a confirmation
entry (y/n key).
Line 520 Returns to the entry start line if the key the user pressed in line 870 is
not the y key.