Installing Your GPIB-SCSI-A and NI-488.2 for Solaris
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Using SCSI Terminating Resistors
Because of its high-speed capabilities, the SCSI bus is sensitive to the electrical
characteristics of the SCSI cabling. When a signal is sent through the SCSI bus,
it bounces back and creates echoes along the cabling. Any device in the middle
of the daisy-chained SCSI bus receives these signal echoes. You should use
terminating resistor packs to prevent echoes and ensure proper termination of a
signal. Read the documentation for each device in your system to find out what
kind of termination it provides.
If your GPIB-SCSI-A is located at the end of an SCSI bus, you can prevent echoes
by leaving the terminating resistor pack installed on one of the ports on the rear
panel of the GPIB-SCSI-A. Also, ensure that the device at the other end of the
SCSI bus (for example, the SCSI host in Figure 4) has a terminating resistor
installed. Remove the terminating resistor packs on all devices except for the one
at each end because SCSI signals are not reliably passed along the SCSI bus after
they reach a device with a terminator.
Caution
Never
connect more than two sets of terminating resistors on an
SCSI bus because more than two sets might overload the signals and
generate errors.
Figure 4 shows where to install terminating resistors if the GPIB-SCSI-A is
located at the end of a system.