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Appendix C Functional Description C-31
The Fast-20 electrical characteristics for the host adapter and target device include:
■ V
il
(input low) equals 1.0 Vdc maximum (signal true)
■ V
ih
(input high) equals 1.9 Vdc minimum (signal false)
■ I
il
(input low current) equals +/- 20 µA at Vi equals 0.5 Vdc
■ I
ih
(input high current) equals +/- 20 µA at Vi equals 2.7 Vdc
■ Minimum input hysteresis equals 0.3 Vdc
C.1.14.2 Supported Target Devices
The SCSI subsystem supports a maximum of four internal devices, including the
host adapter. The CD-ROM drive is a narrow device. A unipack with one drive or a
six-pack, accommodating six drives, can be used as external devices.
TABLE C-7 lists
the target devices supported by the SCSI subsystem.
C.1.14.3 External Cables
External UltraSCSI-compliant SCSI cables have an impedance of 90 ohm (+/- 6 ohm)
and are required for UltraSCSI interface. Sun’s implementation of UltraSCSI requires
that the total SCSI bus length be limited to no more than approximately 20 feet
(6 meters) with up to 12 Sun compensated devices. Due to the considerably short
bus length, an approximate 32-inch (0.8-meter) UltraSCSI-compliant external cable is
supported in addition to an approximate 6.5-foot (2-meter) UltraSCSI-compliant
external cable.
Note – Consult your authorized Sun sales representative or service provider to
order a 0.8-meter or a 2-meter UltraSCSI-compliant external cable.
TABLE C-7 Supported Target Devices
Target Device Comment
Internal disks Up to two 3.5-inch x 1.6-inch disks (4.2-, or
9.1-Gbyte). All internal disks are
UltraSCSI-compliant.
Internal CD-ROM drive Optional 644-Mbyte SunCD 12X speed;
photo CD compatible. Headphone jack with
volume control. CD-ROM drive is a narrow
SCSI device.
Internal tape drive(s) Refer to product guide.
External SPARCstorage UniPack Refer to product guide.
External SPARCstorage SixPack Refer to product guide.