4.1.3 Unit Attention Condition; 4.1.4 Reset Condition - Hitachi DK32EJ - Ultrastar Series 36.9 GB Hard Drive Reference Manual

(2) Tagged Queuing
The host computer can issue plural commands for a logical unit by using the
Queue Tag message. The controller contains a single queue slot which can
enqueue SCSI commands from a single or multiple hosts up to 128 commands.
The controller selects a queued command and executes it based on the command
type of the Queue Tag message specified by the host computer.
The host computer can not issue a tagged command and an untagged command
at a same time, nor issue a duplicated tagged command ( Same tag Number ) at a
same time.

4.1.3 UNIT ATTENTION CONDITION

A unit attention condition occurs whenever the Mode Select parameter or the Log
Select parameter for the logical unit is updated or when the controller is reset (by
the TARGET RESET,SELECTIVE RESET, or power-on reset).
The unit attention condition is informed for the host computers other than that
which updated the Mode Select parameter or for all the host computers when the
controller is reset.
The unit attention state is maintained for each host computer.
Once the controller is put into the unit attention condition, it reports the CHECK
CONDITION status for commands other than the Request Sense and Inquiry
commands. In this case, the controller sets the Unit Attention Sense Key as sense
data. After sending the Check Condition status, the controller enters in the usual
sense data pending state.
When the controller receives an Inquiry command from a host computer in the
unit attention state, it executes the Inquiry command and remains in the unit
attention state.
When the controller receives a Request Sense command from a host computer in
the unit attention state, it sends the pending sense data to the host computer and
remains in the unit attention state.
If there is no pending sense data for the host computer, the controller returns the
sense data containing the Unit Attention Sense Key without reporting the CHECK
CONDITION status. In this case, the unit attention state is cleared.

4.1.4 RESET CONDITION

Reset conditions are used to clear all SCSI data on the SCSI bus immediately.
The reset condition takes precedence over any other phases and conditions.
Once a reset condition occurs, the controller takes the following actions using a
hardware reset option :
· Clears all uncompleted commands.
· Releases all SCSI device reservations.
4 SCSI BUS
OEM MANUAL:K6602771
Revision: 2 / Date: 2002.12.19
Page: 89 / 313