Avago Technologies LSI53C120 - Manual (Page 54)

B-2 Glossary
Bus A collection of unbroken signal lines that interconnect computer modules.
The connections are made by taps on the lines.
C_D/ Control/Data – Driven by a target, indicates Control or Data Information
is on the SCSI Bus. This signal is received by the initiator.
Connect The function that occurs when an initiator selects a target to start an
operation, or a target reselects an initiator to continue an operation.
Control Signals The set of nine lines used to put the SCSI bus into its different phases.
The combinations of asserted and negated control signals define the
phases.
Controller A computer module that interprets signals between a host and a
peripheral device. Often, the controller is a part of the peripheral device,
such as circuitry on a disk drive.
DB0/-DB7/ SCSI Data Bits and Parity Bit – These eight Data Bits (DB0/-DB7/), plus
a Parity Bit (DBP/), form the SCSI Bus. DB7/ is the most significant bit
and has the highest priority ID during the Arbitration Phase. Data parity
is odd. Parity is always generated and optionally checked. Parity is not
valid during arbitration.
Deasserted The act of driving a signal to the false state or allowing the cable
terminators to bias the signal to the false state (by placing the driver in
the high impedance condition).
A signal is deasserted or negated when it is in the state opposite to that
which is indicated by the name of the signal. Opposite of asserted.
Device A single unit on the SCSI bus, identifiable by an SCSI address. It can be
a processor unit, a storage unit (such as a disk or tape controller or
drive), an output unit (such as a controller or printer), or a
communications unit.
Disconnect The function that occurs when a target releases control of the SCSI bus,
allowing the bus to go to the Bus Free phase.
Driver When used in the context of electrical configuration, “driver” is the
circuitry that creates a signal on a line. When used in the context of
software, “driver” is the program that translates commands between the
initiator and target.