Reset Initiated by the Host AdapterThe host adapter will reset the bus if it encounters an error on a SCSI operation thatit cannot recover from. Some examples include: the target goes to an invalid busphase, the host adapter cannot force the target to go bus free when attempting toabort a command, or the host adapter cannot send a bus device reset message. Afterresetting 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 theInterrupt Status register will contain the SCSI ID of the host adapter. The leastsignificant 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 SCSIBus Reset.4. Post completion status of all outstanding commands received prior to the host ac-knowledgment of the Asynchronous Event Notification interrupt. Any commandsthat were outstanding when the SCSI Bus Reset occurred and any commands re-ceived between the reset and the host acknowledgment of the AsynchronousEvent 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 AsynchronousEvent Notification interrupt will be operated on normally.NoteIf the host adapter resets the SCSI bus when attempting a device or host adapterreset (via an Immediate command) the action taken by the host adapter differsfrom that described above. Refer to the Immediate command descriptions for moredetail.Reset Initiated by Another SCSI DeviceIf 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 theInterrupt Status register will contain the SCSI ID of the host adapter. The leastsignificant 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 commandsthat were outstanding when the SCSI Bus Reset was detected and any com-mands received between the reset and the host acknowledgment of theEISA-to-Fast SCSI Host Adapter Enhanced Mode Firmware Description6-47
