Reset Initiated By The Host Adapter; Reset Initiated By Another Scsi Device - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter

Reset Initiated by the Host Adapter

The host adapter will reset the bus if it encounters an error on a SCSI operation that
it cannot recover from. Some examples include: the target goes to an invalid bus
phase, the host adapter cannot force the target to go bus free when attempting to
abort a command, or the host adapter cannot send a bus device reset message. After
resetting the bus, the host adapter will perform the following sequence:
1. Flush Interrupt Queue. The host adapter will post back all commands that com-
pleted prior to the SCSI Bus Reset.
2. Interrupt the host With Asynchronous Event Notification. The host adapter will in-
terrupt the host with asynchronous event status. The SCSI ID in bits 3-0 of the
Interrupt Status register will contain the SCSI ID of the host adapter. The least
significant byte of the Mailbox In registers will contain a value of 22h.
3. Interrupt the host with Completion Status of the command that caused the SCSI
Bus Reset.
4. Post completion status of all outstanding commands received prior to the host ac-
knowledgment of the Asynchronous Event Notification interrupt. Any commands
that were outstanding when the SCSI Bus Reset occurred and any commands re-
ceived between the reset and the host acknowledgment of the Asynchronous
Event Notification interrupt will be returned with error status. The status re-
turned will reflect that the command was aborted by the host adapter (error code:
05). Any commands received after the acknowledgment of the Asynchronous
Event Notification interrupt will be operated on normally.
If the host adapter resets the SCSI bus when attempting a device or host adapter
reset (via an Immediate command) the action taken by the host adapter differs
from that described above. Refer to the Immediate command descriptions for more
detail.

Reset Initiated by Another SCSI Device

If the host adapter detects a SCSI Bus Reset, it will perform the following sequence:
1. Flush Interrupt Queue. The host adapter will post back all commands that com-
pleted prior to the detection of the SCSI Bus Reset.
2. Interrupt the host with Asynchronous Event Notification. The host adapter will in-
terrupt the host with asynchronous event status. The SCSI ID in bits 3-0 of the
Interrupt Status register will contain the SCSI ID of the host adapter. The least
significant byte of the Mailbox In registers will contain a value of 23h.
3. Post completion status of all outstanding commands received prior to the host ac-
knowledgment of the Asynchronous Event Notification interrupt. Any commands
that were outstanding when the SCSI Bus Reset was detected and any com-
mands received between the reset and the host acknowledgment of the
Enhanced Mode Firmware Description
Note
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