Table of Contents
Advertisement
CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
4. Logical Characteristics
The logical characteristics of the controller comply with ANSI X3.131-1986
for a single-ended asynchronous implementation.
The controller supports
disconnect/reselect.
Several additional logical characteristics are discussed
here to aid in understanding the operation of the drive and controller.
4 . 1. Condi tions
TQis section describes certain conditions as they relate to the operation of
the drive and the interface.
4.1.1. Power-on Condition
The power-on condition occurs when power is first applied to the unit.
The
controller performs power-on diagnostics.
If a caddy
is inserted the drive
loads the caddy and attempts to read the table of contents.
For the duration
of the power-on condition the controller will return BUSY status.
If a
failure in power-on diagnostics occurs the controller will return CHECK
CONDITION STATUS.
If after the caddy is inserted it does not seat properly,
or the drive is unable to focus, or the drive is unable to achieve spindle
lock-up or the table of contents is not recovered the controller will return
a CHECK CONDITION STATUS.
4.1.2. Reset Condition
The reset condition occurs whenever the RST signal is asserted, or a BUS
DEVICE RESET message is received.
4.1.3. Unit Attention Condition
The unit attention condition occurs following a power-on condition, a reset
condition, the insertion of a caddy with the successful recovery of the table
of contents or the receipt of a MODE SELECT command from another initiator.
The unit attention condition will persist for each initiator until that
initiator issues a command to the logical unit for which the controller
returns a CHECK CONDITION status.
If the next command from that initiator to
the logical unit (following the CHECK CONDITION status) is REQUEST SENSE, then
the UNIT ATTENTION sense key is returned.
If any command other than REQUEST
SENSE is received, the unit attention condition is lost.
If more than one unit attention condition occurs the unit attention
condition with the highest priority will be reported.
The priority is
1) Power on / reset
2)
Not ready to ready
transi~~en
(medium change)
3) MODE SELECT command istnea-trom another initiator
If an INQUIRY command is received from an initiator with a pending unit
attention condition the controller will perform
th~
INQUIRY command and will
not clear the unit attention condition.
If a REQUEST SENSE command is received from an initiator with a pending unit
attention condition then the controller will discard any pending sense data,
report UNIT ATTENTION sense key, and clear the unit attention condition for
4-1
Advertisement
Table of Contents
