Chapter2 Installation
GPIB-SCSI-Afor Solaris 2-6 ni.com
Using SCSI TerminatingResistors
Because of its high-speed capabilities, the SCSI bus is sensitive to the
electricalcharacteristics 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.Y ou 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.
Ifyour GPIB-SCSI-A is located at the end of an SCSI bus, you can prevent
echoesby leaving the terminating resistor pack installed on one of the ports
on the rear panelo fthe GPIB-SC SI-A. Also, ensure that the deviceat the
other end of the SCSI bus(for example, the SCSI h ost in Figure 2-4) has
aterminating resistor installed. Remove the terminating resistor packs on
alldevices except for the one at each end because SCSI signals are not
reliablypassed along the SCSI bus after they reach a device with a
terminator.
Caution Neverconnect more than two sets of terminating resistors on an SCSI bus because
more than twosets might overload the signals and generate errors.
GS.book Page 6 Tuesday,June 12, 2001 2:17PM