Fujitsu 80, Scsi Logical Interface Specifications

Page: 32 / 310

Command Processing
1-14 C141-C010
Note:
In disconnect processing in this case, transfer of all the data accompanying execution of the
command is complete and there is actually no necessity for the SAVE DATA POINTER
message.
However, by issuing the SAVE DATA POINTER message, processing time increases due to the
message transfer, but as a result of the pointer restore operation that is executed internally by the
INIT during reconnection processing for the status report, the current data pointer can reflect the
final results of the data transfer.
(5)
Disconnect processing exceptions
When the previously mentioned disconnect processing is executed, if the ATTENTION condition is generated
for the DISCONNECT message sent by the IDD and the INIT returns the MESSAGE REJECT message, the
IDD executes the command with the connections to the SCSI bus remaining as is, without executing disconnect
processing. Cases of disconnect processing in which a pointer operation is necessary and the SAVE DATA
POINTER message is rejected are the same.
(6)
Reconnection processing procedure
The reconnection processing procedure is as shown below.
1) The IDD executes the ARBITRATION phase at the point when processing on the SCSI bus is
necessary and gets the SCSI bus control right, then reconnects with the INIT in the RESELECTION
phase.
2) After that, the IDD sends the IDENTIFY message to the INIT and notifies it of the logical unit
number (LUN) necessary for reconnection processing. If a tagged queuing command is executed, the
IDD sends the SIMPLE message to inform the INIT of the tag ID. The INIT reads the Saved pointer
(command, data and status) corresponding to the LUN specified at this time and restores it to the
current pointer.
Note:
1) If there is no response from the INIT within the specified time (default: 250 ms) in the
RESELECTION phase, the IDD performs timeout processing, then enters the BUS FREE
phase. In this case, after waiting 200 ms or longer, the IDD executes the predetermined
number of retries (re-executing the RESELECTION phase). However, if it still cannot
reconnect with the INIT after that, the IDD clears the command necessary for reconnection
processing and generates sense data indicating ABORTED COMMAND[=B]/Select
/Reselect failure[=45-00].
2) If the INIT rejects the IDENTIFY message, or if it rejects the SIMPLE message when
executing a tagged queuing command, the IDD clears the command that was being
executed during reconnection processing and enters the BUS FREE phase. In this case, the
IDD generates sense data indicating ABORTED COMMAND[=B]/Message error[=43-00].