Tektronix 2714, Programmer'S Manual

Page: 251 / 308

Programming
2714 & 2715 Programmer Manual
6–53
An alternative approach to plotting the spectrum analyzer screen data enables
you to create independent input and output subroutines for use with specific
devices, and to share those devices with other instruments on the GPIB. This
approach involves returning the screen plot data to the controller, then sending it
to the designated output device. The program does not proceed until the plot data
is received, so it is not necessary to
WAIt
for an end-of-sweep SRQ. Further, this
approach enables you to do the printing or plotting at a more convenient time or
use an entirely different controller and output device.
Figure 6–8 and Figure 6–9 show how you might return and print or plot
instrument data. Each “Do it” in the diagrams can represent a separate subroutine
for a specific device.
Example 6–6 shows a subroutine for obtaining screen plot data from the 2714 or
2715 using the
PLOT?
query. It does not store the data on disk (you can add that
capability if desired), but holds the data in memory as the string variable
PLOT.DAT$
.
The length of the string required depends on the display acquisition mode, the
plotter type, and the number of registers displayed. 12 kbyte of memory is
enough for a single sweep in PEAK acquisition mode if an HPGL plotter is used.
If an Epson FX printer is used, as many as 61.1 Kbyte may be required for four
sweeps in MAX/MIN mode. Substitute
61100
for
12000
and change
HPGL4
to
EPSON
if using an Epson FX printer.
Specify
HPGL2
if you have a 2-pen plotter. Data may be sent to a parallel
Epson-type printer on the controller’s parallel port, but to send it over the GPIB,
the printer must be equipped with a GPIB board (an unlikely but possible
configuration).
The
SEND.PLOT
subroutine transmits
PLOT.DAT$
to an HPGL 4-pen plotter
matching the type specified in
GET.PLOT
. Note that the controller timeout is
disabled, and execution following the plot is restarted by pressing any key.