Supported Options• Flag Word 1 - Scatter/Gather (bit 12) is supported. Suppress Error on Underrun(bit 10) should be used with care since the exact length of the transfer may not beknown. Disable Status Block (bit 14) should also be used with care since thestatus block will return information regarding the actual command received. TheAutomatic Request Sense flag (bit 15) is ignored - if the host adapter returns theinitiator a check condition, the sense information will automatically be stored inhost memory pointed to by the sense information pointer. If the host has no needfor the sense information, a zero should be stored in the sense length field. Allother flags should be zero.• Flag Word 2 - Logical Unit Number (bits 2-0), Data Transfer (bit 8) and Directionof Transfer (bit 9) are supported. All other flags should be zero. The following ta-ble shows the relationship between the Data Transfer and Direction flags.Direction Data Transfer DescriptionX 0 Invalid. Specification error.0 1Receive command expected. The host adapter willenter a data in phase. (Data transfer from hostmemory to initiator.)1 1Send command expected. The host adapter will entera data out phase. (Data transfer from initiator to hostmemory.)X indicates don’t careAborting Control Block CommandsThe Attention register provides a means for aborting an outstanding control block op-eration. The address of the control block to be aborted is stored into the Mailbox Outregisters, least significant byte first. The Attention register is then stored with thefollowing value:7 6 5 4 3 2 1 00 1 0 1 SCSI IDThe SCSI ID specifies the SCSI address of a particular target or initiator.When the Attention register is written to, the host adapter is interrupted. The hostadapter then scans its internal control block queue for a control block that has an ad-dress that matches the one stored in the Mailbox Out registers. If the associated con-trol block is not found, the abort is ignored and no interrupt will be posted back tothe host. If the associated control block is found, the host adapter will take the follow-ing action based on the current progress of the operation.EISA-to-Fast SCSI Host Adapter Enhanced Mode Firmware Description6-39
