Quantum Q250 User Manual

SCSI commands relieve the host system of many tasks, such as defect
management, error correction, and physical sector addressing.
Programmable options allow users flexible ways to handle defects
initially and throughout the product's life. For example, (1)
defective sectors can be automatically reassigned without the need
to reformat, (2) data can be corrected with a Reed-Solomon error
correcting code (ECC) , or (3) all error detection and correction can
be handled in the host computer. The ECC can correct one burst error
of 17 bits, or detect three burst errors of 17 bits each.
Q200 Series
tm
drives employ a hard-sectored format with servo data
factory-written in wedges between all sectors on all surfaces. Thus,
thermal and mechanical effects which tend to misalign heads on the
headstack assembly are minimized, in comparison with other drives
which use a dedicated servo surface. In addition, conservative linear
bit and track densities ensure high data integrity. Logical block
sizes of 512, 1024, and 2048 bytes are supported.
1.2
Logic Conventions
Signals on the SCSI bus are all true or asserted when they are at low
level, and false or non-asserted when they are at high level. In this
document, the names of such signals are always preceded by a minus, as
"-ACK," and the timing diagrams are drawn to show the signals asserted
when they are low, as they might be observed with an oscilloscope.
other signals, as on the PCB, are indicated as follows:
Signal Type
Asserted when low
Asserted when high
Differential
Analog
Examples
-paR
+POR
Asserted when +READ SIG is more
positive than -READ SIG
WRITE CURRENT, 5 V
Note that the ANSI Standard for SCSI, ANSI X3.131-1986 uses, for
example, "-ACK" when listing connector pin connections, but describes
the signals as "ACK" in the text, and shows positive true signals
"+ACK" on timing diagrams.
1-2

Quantum Q250 Specifications

General

Brand	Quantum
Model	Q250
Category	Storage
Language	English