Digital Equipment StorageWorks UltraSCSI DS-BA370 Series, User Manual

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Glossary
Glossary–2 UltraSCSI RAID Enclosure
bus expander
Devices that couple bus segments together without any impact on the SCSI
protocol, or the software. These devices include both single-ended to
differential and single-ended to single-ended bus extenders. The term
extender is a general term that includes “extender,” “repeater” and
“isolator.”
bus extender
See bus expander.
bus segment
A SCSI bus segment consists of all the conductors and connectors required
to attain signal line continuity between every driver, receiver, and two
terminators for each signal. It is not necessary that a SCSI bus segment
contain any initiators or targets, but it must have at least two devices
attached. (Drivers and receivers may be part of extenders as well as part
initiators and targets.)
Bus segments can be either single-ended (SE) or differential (DF). The
terminator properties determine the bus segment type.
____________________ Caution ____________________
The device transceiver type (single-ended or differential) must
match the bus segment type. Devices that do not meet this
condition cannot operate.
________________________________________________
The allowed length of a bus segment depends on the electrical loading,
transmission media type, and data transfer rate. In many cases, heavier
loading, smaller wires, and higher speeds demand shorter lengths.
Increasing the number of devices in a given length of the bus, by using
longer stubs, or higher capacitance devices produces loading.
bus segment types
The following are the SCSI bus segments types:
•
Single-ended (SE)
•
High voltage differential (HVD)