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Requirements for Connecting a SCSI Cable
The cable for connecting the tape drive to the SCSI bus is not
provided with the tape drive. You must provide a cable that complies
with the appropriate safety and regulatory agency requirements. To
comply with FCC, Canadian DOC, and VDE limits, the tape drive
requires shielded cables when the cables are external to the mounting
enclosure.
Impedance
Ideally, to match the cable terminators, the cable should have a
characteristic impedance of 122 ohms (differential) or 132 ohms
(single-ended). However, since cables with this high of a characteristic
impedance are not generally available, somewhat lower impedances
are acceptable. A characteristic impedance of 100 ohms ± 10% is
recommended for unshielded flat or twisted-pair ribbon cable. A
characteristic impedance greater than 90 ohms is recommended for
shielded cables.
#
Important To minimize discontinuities and signal reflections,
Exabyte recommends that cables used on the same bus have the
same impedances.
Cable Length
The maximum length of the SCSI cable depends on whether you are
using a single-ended or differential SCSI configuration, as follows:
For single-ended SCSI configurations, the maximum allowable
bus length is 6 meters (19.7 feet). A stub length of no more than
0.1 meters (4 inches) is allowed off the mainline interconnection
within any connected equipment.
For differential SCSI configurations, the maximum allowable bus
length is 25 meters (82 feet). A stub length of no more than
0.2 meters (8 inches) is allowed off the mainline interconnection
within any connected equipment.
May 1994 EXB-8205 and EXB-8505 4-7
(Standard and XL)
4 Requirements for Use