HP C2246 Technical Reference Manual page 32

Cabling Requirements
The disk drive adheres to the cabling requirements and limitations set forth in the ANSI SCSI
specifications. Refer to the SCSI specifications for additional details.
• Cables with a characteristic impedance of 100 ohms ±10% are recommended for unshielded
fiat or twisted pair ribbon cable.
• Cables with a characteristic impedance of 90 ohms ±10% are preferred for shielded cables.
• To minimize discontinuities and signal reflections, do not use cables with different
impedances on the same bus.
• A minimum wire size of 28 AWG should be used to minimize noise effects and ensure pi:oper
distribution of termination power. Note: because of physical size limitations of current
connector designs, a wire size of 30 AWG should be used for wide differential cabling.
• Cables must be properly terminated.
Single-ended Cable
• A 50-conductor flat cable or 25-signal twisted-pair cable should be used. Cable length
should be equal to or less than 6.0 meters. This refers to internal and external cable length
(except stubs).
• A stub length of no more than 0.1 meter is allowed off the main line interconnection within
any connected device.
Differential Cable
• For narrow differential drives, a 50-conductor flat cable or 25-signal twisted-pair cable
should be used. For wide differential drives, a 68-conductor flat cable or 34-signal twisted
pair cable should be used. Twisted pair cabling is preferred to minimize noise. Cable length
should be equal to or less than 25 meters. This refers to internal and external cable length
(except stubs).
• A stub length of no more than 0.2 meter is allowed off the main line interconnection within
any connected device.
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