Quantum PowerStor L200, User Manual

Page: 69 / 112

Chapter 5 SCSI Interface
General SCSI Bus Operation
Quantum|ATL PowerStor L200 Series Library User’s Guide 53
Unit Attention
Condition
5
Queued unit attentions are implemented on this device, and are
maintained separately for each Initiator. Unit attentions are created
in the following circumstances:
• Power on
• Bus reset
• Bus device reset message
• Asynchronous media change
• Another initiator changed the mode parameters
It is not unusual for a firmware (microcode) update to complete
two queued unit attentions. Due to a limited number of unit
attention buffers, if an initiator does not clear unit attentions
queued for it, at some point the library stops generating new unit
attentions for that initiator-LUN (I-L) combination. Existing ones
are left queued.
Behavior Around
Power-On and
SCSI Bus Reset
5
All device SCSI lines go to a high-impedance state when the library
is turned off.
The library does not generate any spurious signals on the SCSI bus
when it is turned on.
Within 5 seconds of being turned on, and within 250 milliseconds
(typically under 4 ms) after a bus reset, the library responds to
SCSI bus selections and returns appropriate, normal, responses.
Tape motion commands are returned with a
Check Condition
status,
Sense Key Not Ready
, until the media has been made
ready.
The hard bus reset option is implemented.
The library recognizes multiple bus resets in succession and bus
resets of arbitrarily long duration. It recovers within the time limits
specified above, following the last bus reset.