Avago Technologies LSI53C180 - Manual (Page 65)

B-3
External
Configuration All SCSI peripheral devices are external to the host enclosure.
External
Terminator The terminator that exists on the last peripheral device that terminates the
end of the external SCSI bus.
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.
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 a 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 A 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. I/O 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.
I/O Cycle An I/O cycle is an Input (I/O Read) operation or Output (I/O Write)
operation that accesses the PC Card’s I/O address space.
Logical Unit The logical representation of a physical or virtual device, addressable
through a target. A physical device can have more than one logical unit.
Low (logical
level) A signal is at the low logic level when it is below approximately 0.5 volts.