OEM MANUAL:K6602924
3 SCSI BUS
Revision: 1 / Date: 2003.03.06
Page: 33 / 273
3.1.4 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 Bus Device Reset message, hardware 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.
3.1.5 ATTENTION CONDITION
The host computer informs the controller that it is ready to send a message to the
controller by using an attention condition.
Except in the Arbitration and Bus Free phases, the host computer can generate
attention conditions asynchronously by asserting ATN signal.
3.1.6 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.
The host computer can generate reset conditions asynchronously by asserting and
holding on RST signal for the minimum reset hold period.
This SCSI controller cannot generate the RST signal.
