Appendix C Application Examples - National Instruments GPIB-232CV-A User Manual

Application Examples
Using the GPIB-232CV-A as a High-Speed Print Spooler
© National Instruments Corporation
This appendix contains two GPIB-232CV-A application examples. The
first example shows how to use the GPIB-232CV-A as a high-speed print
spooler, and the second example shows how to connect a HP7475 GPIB
plotter to an IBM PC running AUTOCAD.
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.
With a GPIB-232CV-A, you can transfer data at GPIB rates instead of
RS-232 rates. The GPIB-232CV-A uses a DMA Controller to input data
from the GPIB port to the RAM buffer and can input GPIB data at rates up
to 625 kbytes/s. 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-A 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 . Use the following procedure to set up the system the first
ibconf
time:
1. Use to configure the system so that a device named either
ibconf
printer or plotter is connected to the GPIB interface board. Be sure to
enable DMA transfers and to use high-speed timing.
2. Configure the GPIB-232CV-A to operate in D mode with the small
(256 bytes) serial port buffer and SRQ disabled. The serial buffer is set
to the smallest size to allow the GPIB port, which is the data source,
to use the majority of RAM. Set the GPIB address to the same address
C-1
C
GPIB-232CV-A User Manual