HP C737990900 - Manual (Page 23)

Interface Implementation 23
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still tied low, so in this case it will use the soft name last downloaded. This
will allow drive access without confusing the host.
Field Replaceable Units
An FRU code identifies which part of the hardware is considered to have
failed. These codes turn up in sense data byte 14 and as the sense code
qualifier for sense codes 4400h (internal target failure) and 40XX (diagnostic
failure).
Although there are no actual Field Replaceable Units on HP Ultrium drives, the
following sub-assemblies can be replaced at Repair Centres:
Descriptions of Signals
(Parallel SCSI only)
The SCSI interface consists of 27 signals—9 control lines, 16 data lines and 2
parity lines. A description of these signals is given in the following table.
■
Drive PCA
■
Head Assembly
■
Mechanism
■
Front Panel
Signal Name Driven by Description
-BSY
Busy — OR-tied signal used to indicate that the SCSI bus is in use.
-SEL
Select Initiator
Target
Used to select a target during the Selection phase.
Used to select an initiator during the Reselection phase.
-C/D
Control/Data Target Indicates whether control or data information is on the data
bus.
True (low) Control information
False (high) Data information
-I/O
Input/Output Target Controls the direction of data movement on the bus with
respect to the Initiator. This signal is also used to distinguish
between Selection and Reselection phases.