National Instruments GPIB-232CV, Руководство пользователя

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© National Instruments Corp. C-1 GPIB-232CV User Manual
Appendix C
Application Examples
This appendix contains two GPIB-232CV application examples. The first
example shows how to use the GPIB-232CV as a high-speed print spooler,
and the second example shows how to connect a HP7475 GPIB plotter to an
IBM PC running AUTOCAD.
Using the GPIB-232CV as a High-Speed Print
Spooler
Because mechanical printers and plotters are slow relative to the processing
speed of a computer, computers must output data at a slow rate. This forces
you to wait for the data to be output or tolerate decreased performance if the
data transfer occurs in the background. One common solution to this
problem is to use a print spooler to relieve the computer of this task.
Standard print spoolers are able to store incoming data in a RAM buffer
until the printer or plotter is able to accept it, allowing the PC to output data
at a rate faster than printer or plotter rates. You can use the GPIB-232CV
in this way.
With a GPIB-232CV, you can transfer data at GPIB rates instead of RS-232
rates. The GPIB-232CV uses a DMA Controller to input data from the
GPIB port to the RAM buffer and can input GPIB data at rates up to 900
kbytes/sec. Therefore, the transfer rate is limited only by the rate at which
the GPIB Talker can write data.
This example shows you how to connect and use your GPIB-232CV as a
high-speed print spooler which returns control to you quickly, so that you
do not have to wait for the PC to finish printing or plotting a file.
The following example is based on the assumption that a National
Instruments GPIB interface board (such as the AT-GPIB) is installed in
your computer and that you are familiar with the software configuration
utility
ibconf
. Use the following procedure to set up the system the first
time.