Avago Technologies LSI53C120 - Manual (Page 55)

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External
Configuration All SCSI peripheral devices are external to the host enclosure.
External
Terminator The terminator that exists on the last peripheral subsystem that
terminates the external end of the SCSI bus.
Exit-Point
Terminator A Terminator that may be enabled or disabled which exists at the 50-
position high-density connector on hosts that support a mixed
configuration (combination of internal and external SCSI peripheral
devices).
Free In the context of Bus Free phase, “free” means that no SCSI device is
actively using the SCSI bus and, therefore, the bus is available for use.
Gigabyte One billion bytes; equal to one thousand megabytes.
High (logical
level) A signal is in the high logic state when it is above approximately 2.5 volts.
Host A processor, usually consisting of the central processing unit and main
memory. Typically, a host communicates with other devices, such as
peripherals and other hosts. On the SCSI bus, a host has an SCSI
address.
Host Adapter Circuitry that translates between a processor's internal bus and a
different bus, such as SCSI. On the SCSI bus, a host adapter usually
acts as an initiator.
Initiator An SCSI device that requests another SCSI device (a target) to perform
an operation. Usually, a host acts as an initiator and a peripheral device
acts as a target.
Internal
Configuration All SCSI peripheral devices are internal to the host enclosure.
Internal
Terminator The terminator that exists within the host that terminates the internal end
of the SCSI bus.
I/O/ Input/Output – Driven by a target, controls the direction of data transfer
on the SCSI Bus. When active, this signal indicates input to the initiator.
When inactive, this signal indicates output from the initiator. This signal
is also used to distinguish between the Selection and Reselection
Phases.