Chapter 2
Installation
2-6
ni.com
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 2-4) 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.
GS.book Page 6 Tuesday, June 12, 2001 2:17 PM
