Seagate Ultra 320 - Manual (Page 123)

Parallel SCSI Interface Product Manual, Rev. A 109
The effect of the hard reset on tasks that have not completed, SCSI device reservations, and SCSI device
operating modes is defined in the SCSI Architecture Model-4 standard.
Any SCSI device that detects a hard reset shall also set its transfer agreement to the default transfer agree-
ment.
5.4 Reset events
When a SCSI device detects a reset event it shall initiate hard reset.
5.4.1 Bus reset event
When a SCSI device detects a bus reset condition by detecting RST true for a reset delay, it shall cause a
reset event. In response to a bus reset event, a SCSI target port shall create a unit attention condition for all ini-
tiators. The sense key shall be set to Unit Attention with the additional sense code set to either SCSI Bus
Reset Occurred or Power On, Reset, or Bus Device Reset Occurred.
5.4.2 Power on reset event
When a SCSI device is powered on, it shall cause a reset event. In response to a power on reset event, the tar-
get shall create a unit attention condition for all initiators. The sense key shall be set to Unit Attention with the
additional sense code set to either Power On Occurred or Power On, Reset, or Bus Device Reset Occurred.
5.4.3 Target reset event
When a SCSI device successfully receives a SCSI target port Reset message, it shall cause a reset event. In
response to a SCSI target port reset event, the SCSI target shall create a unit attention condition for all SCSI
initiator ports. The sense key shall be set to Unit Attention with the additional sense code set to either Bus
Device Reset Function Occurred or Power On, Reset, or Bus Device Reset Occurred.
5.4.4 Transceiver mode change reset event
When a SCSI device that contains multimode transceivers detects a transceiver mode change from LVD mode
to MSE mode it shall cause a reset event. In response to the transceiver mode change reset event, a SCSI tar-
get port shall create a unit attention condition for all initiators. The sense key shall be set to Unit Attention, and
the additional sense code set to Transceiver Mode Changed to Single-ended.
When a SCSI device that contains multimode transceivers detects a transceiver mode change from MSE
mode to LVD mode it shall cause a reset event. In response to the transceiver mode change reset event, a
SCSI target port shall create a unit attention condition for all initiators. The sense key shall be set to Unit Atten-
tion, and the additional sense code set to Transceiver Mode Changed to LVD.
5.5 Asynchronous condition recovery
Part of the asynchronous condition recovery stem are sets of pointers to storage areas where information is
kept that, in addition to being necessary to the start of a task, allows tasks to be interrupted, restarted or
repeated. The following subsections describe these pointers.
5.5.1 SCSI pointers
The SCSI architecture provides for sets of pointers to be kept within each initiator task control area. These
pointers are in sets of three pointers per set. The pointers in each set point to three storage area sections in the
initiator. The three sections contain the following information:
a. A command from initiator to target.
b. Status (from target) associated with the command.
c. Data (to/from target) associated with the command.
Of these three-pointer sets there are two types: