Avago Technologies LSI53C180 User Manual
Page 64
B-2
Glossary
Cable Skew
Delay
Cable skew delay is the minimum difference in propagation time allowed
between any two SCSI bus signals measured between any two SCSI
devices.
C_D/
Control/Data – Driven by a target. When asserted, 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.
DB[7:0]/
SCSI Data Bits – These eight Data Bits (DB[7:0]/), 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 a 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.
Differential
A signaling alternative that employs differential drivers and receivers to
improve signal-to-noise ratios and increase maximum cable lengths.
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.