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Chapter 2. Preparing the Host System
22
Selecting a SCSI Bus for the Library
(SCSI Libraries Only)
The single-ended/low-voltage differential (SE/LVD) library operates in either single-
ended or low-voltage differential SCSI mode, depending on the type of bus that is
attached. When attached to a single-ended SCSI adapter, it will operate within the
maximum specifications for that bus type.
Note: The entire bus (including host bus adapter, devices and
termination) must be configured for LVD operation in order to
operate in LVD mode. Attaching any single-ended SCSI device to
an LVD bus renders the entire bus (and all attached devices)
subject to the maximum specification requirements for
single-ended SCSI (including maximum cable lengths).
The terminator shipped with the SE/LVD library can function in either mode. To check
the mode in which your library is operating, look at the library terminator and the
terminator’s light-emitting diode (LED). The top of the terminator lists the color of the
LED for each mode.
Note: The HVD library includes an active HVD terminator.
SCSI specifications for LVD, SE, and HVD modes are shown in this table:
Determining SCSI ID Usage
Each device on the SCSI bus to which the library is attached must have its own SCSI
ID. Examine your host system and attached devices to determine which SCSI IDs are
SCSI Specifications LVD Mode SE Mode HVD Mode
SCSI Bus Width 16 bits 16 bits 16 bits
Maximum Bus Speed 80 MB/sec 40 MB/sec 40 MB/sec
Maximum Bus Cable Lengths 12 meters
a
1.5 meters
a
25 meters
a
a
Maximum cable length requirements include the internal cabling for each device. (The library contains 60 centimeters [24 inches]
of cabling inside the library.)