HP 220mx HP SureStore 220mx Optical Jukebox User's Guide - Page 84

LUN Addressing, Transfer Rates on the Bus, Termination

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Operating This Jukebox on a SCSI Bus A Brief Overview of SCSI LUN Addressing This jukebox does not support logical unit numbering (LUN) addressing. Transfer Rates on the Bus Initially, the SCSI specification defined a 5 MB/s synchronous data transfer rate on the narrow bus. SCSI now also defines "Fast" which is 10 MB/s on a narrow bus and 20 MB/s on a wide bus. Another definition is "Ultra," also known as "Fast-20" which is 20 MB/s transfer rate on a narrow bus and 40 MB/s on a wide bus. Termination To keep signals on the SCSI bus from being reflected, "terminators" must be placed at each end of the physical bus. These terminators may be either active or passive. Passive termination is a resistor network. Active termination uses a voltage regulator (the active component) to regulate the power of the resistor network to provide more stable termination. Active termination is always preferred over passive termination. Depending on your SCSI device, termination is supplied by a using a physical connector, by flipping a dip switch, or by selecting the termination setting in software. Termination is always at both physical ends of the bus. (Note that all HP jukeboxes use active termination.) B- 4 Appendix B

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B-4
Appendix B
Operating This Jukebox on a SCSI Bus
A Brief Overview of SCSI
LUN Addressing
This jukebox does not support logical unit numbering (LUN) addressing.
Transfer Rates on the Bus
Initially, the SCSI specification defined a 5 MB/s synchronous data
transfer rate on the narrow bus. SCSI now also defines
“
Fast
”
which is 10
MB/s on a narrow bus and 20 MB/s on a wide bus. Another definition is
“
Ultra,
”
also known as
“
Fast-20
”
which is 20 MB/s transfer rate on a
narrow bus and 40 MB/s on a wide bus.
Termination
To keep signals on the SCSI bus from being reflected,
“
terminators
”
must
be placed at each end of the physical bus. These terminators may be
either active or passive. Passive termination is a resistor network. Active
termination uses a voltage regulator (the active component) to regulate
the power of the resistor network to provide more stable termination.
Active termination is always preferred over passive termination.
Depending on your SCSI device, termination is supplied by a using a
physical connector, by flipping a dip switch, or by selecting the
termination setting in software.
Termination is always at both physical ends of the bus. (Note that all HP
jukeboxes use
active
termination.)