Asynchronous Event NotificationAn asynchronous event occurs when the host adapter detects an unexpected condi-tion on the SCSI subsystem.Asynchronous Event Conditions• A SCSI bus reset has occurred• The host adapter was selected by another initiatorThe host adapter notifies the host of an asynchronous event via an interrupt. Whenthe host detects the interrupt, the Interrupt Status register will contain the followingvalue:7 6 5 4 3 2 1 01 1 0 1 SCSI IDThe SCSI ID specifies either the SCSI address of a particular device on the subsys-tem, or the SCSI address of the host adapter. The host adapter’s ID can be found inbits 3-0 of the SCSI Definition register.Prior to interrupting the host, the host adapter will store additionl information in theMailbox In registers.SCSI Bus ResetIf a SCSI bus reset has occurred, the SCSI ID in the Interrupt Status register will bethe host adapter’s ID. The Mailbox In registers will contain the following information:F E D C B A 9 8 7 6 5 4 3 2 1 0 F E D C B A 9 8 7 6 5 4 3 2 1 0Reset CodeThe least significant byte contains the reset error code. The three most significantbytes will be zero. Possible Reset error codes:Code Description22 SCSI Bus Reset by Host Adapter23 SCSI Bus Reset by Other DeviceFor more information on how the host adapter handles SCSI resets, refer to the sec-tion titled SCSI Bus Reset Handling.EISA-to-Fast SCSI Host Adapter Enhanced Mode Firmware Description6-41
