Aborting Control Block Commands - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter
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 be
known. Disable Status Block (bit 14) should also be used with care since the
status block will return information regarding the actual command received. The
Automatic Request Sense flag (bit 15) is ignored - if the host adapter returns the
initiator a check condition, the sense information will automatically be stored in
host memory pointed to by the sense information pointer. If the host has no need
for the sense information, a zero should be stored in the sense length field. All
other flags should be zero.
Flag Word 2 - Logical Unit Number (bits 2-0), Data Transfer (bit 8) and Direction
of 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
X
0
1
X indicates don't care

Aborting Control Block Commands

The 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 Out
registers, least significant byte first. The Attention register is then stored with the
following value:
7
0
The 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 host
adapter 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 to
the 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.
Data Transfer Description
0 Invalid. Specification error.
Receive command expected. The host adapter will
1 enter a data in phase. (Data transfer from host
memory to initiator.)
Send command expected. The host adapter will enter
1 a data out phase. (Data transfer from initiator to host
memory.)
6 5 4
1 0 1
Enhanced Mode Firmware Description
3 2
SCSI ID
1 0
6-39