Status Bytes
MESSAGE REJECT
6.5. Abort Message Handling
If after a MESSAGE-IN phase the Iilitiatorasserts ATN and transfers an ABORT message, then the Drive will immediately go to the BUS FREE phase. No Status or ending Message will be sent. The Drive will remain in its current state (MODE settings and current tape position must be kept).
When receiving a new command, the Drive will be able to continue where that last aborted command left oft'.
See Section 4.6. (Overlapped Command Handling) for a description of ABORT in overlapped command situations.
See also the Section on LOGICAL CHARACTERISTICS for details on ATN signal handling. The following is true for all commands:
• If the ABORT message is transferred before the Drive enters the Command phase, then the Drive will just go to the BUS FREE phase, effectively ignoring the whole selection •
• If the ABORT message is transferred immediately after the Com-mand phase (ATN must be aSserted during comCom-mand transfer), then the Drive will just go to the BUS FREE phase, effectively ignoring the whole command. This is true even if the Drive detects errors in the command block aike Bus Parity Error}.
SCSl-2 Functional Specifications
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".
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The following table describes ABORT-handling in non-overlapped com-mand situations for all commands when the ABORT-message is trans-ferred at any later stage in the phase'sequencing.
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ActionThe COPY command will not be performed if the command is aborted before the Drive has disconnected from the originallnitia-tor (A TN must be asserted during the parameter data transfer, during SAVE POINTER or DISCONNECT messages). H the COPY command is aborted at any later stage, the Drive will immediately stop Issuing commands to the direct access device, effectively aborting the copy operation (there is no way for the original Initiator to get information on the data actually copied).
These commands continues to execute as if executed In Immedl-ate (or buffered) mode. They will, however, not be executed if they follow a READ or WRITE command that executed success-fully. In this case they are ignored.
The WRITE FILEMARK command will be ignored if it is aborted when it is about to disconnect. Note, however, that a Referrmcs
Tracie will be written if the WRITE FILEMARK command was Is-sued while the tape was positioned at BOT. Note also that the WRITE FILEMARK command a/ways disconnects as soon as the command descriptor block has been transferred. When the WRITE FILEMARK command is aborted during re-connecting (or later), it has already been executed.
These commands will be executed (the parameter data has al-ready been transferred, the ABORT came to late). Note that for the REQUEST SENSE command the parameter data is usually lost. The other commands may be executed again to get the parameter data once more.
REQUEST BLOCK ADDRESS REQUEST SENSE
RECEIVE DIAGNOSTIC RESULTS
MODE SELECT The actual mode selection will not be performed if the command is aborted Immediately after the parameter data transfer (A TN must be asserted during the data transfer). If the MODE SELECT command disconnects after parameter data transfer, then it will also be possible if the command is aborted in any later phase, the mode selection will, however, already have been performed.
PREVENT/ALLOW MEDIA REMOVAL These commands will be executed (the ABORT came to late).
RELEASE UNIT RESERVE UNIT TEST UNIT READY
Table: Non-overlapped ABORT Message Handling (to be continued ... )
6-9 SCS/-2 Functional Specifications
Tandberg Data Message System
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CommandI
ActionREAD If the command is aborted immediately after a data transfer (ATN must be asserted durlngthe data transfer), the next Read opera-tion will start on the following block. The Initiator may request sense information (Block Counter) to check the actual number of blocks read.
READ BUFFER This command will be aborted after the last data transfer. The command may be Issued again to retransfer the last
transferred data and also the data not transferred when the command was aborted.
RECOVER BUFFERED DATA If the command is aborted immediately after the data transfer (A TN must be asserted during the data transfer), the data trans-ferred will not be removed from the buffer. This means that in this situation It will be possible to issue the command once more to transfer the same data once more.
If the command is aborted in any later phase the data will have been taken out of the buffer (the data is lost).
SEEK BLOCK The actual seek operation will not be performed If the command is LOCATE aborted immediately after the parameter data transfer (A TN must
be. asserted during the data transfer).
If the command is aborted in any later phase, the seek operation will execute as If the command where executed in immediate mode.
SEND DIAGNOSTICS The actual diagnostic operation will not be perforrnedif the com-mand is aborted immediately after the parameter data transfer (A TN must be asserted during the data transfer). If the command is aborted later, the diagnostic operation has, however, already been performed.
SPACE The space operation will be terminated immediately. Note how-ever, that if the Drive does not disconnect and ATN Is asserted some time after the command phase, the complete space opera-tion will usually have completed before the Drive tests the ATN line (the Drive tests for ATN only when changing bus phases).
The Initiator may request sense information (Block Counter) to check the actual number of spaced blocks.
VERIFY If the command is aborted immediately after a data transfer (ATN must be asserted during the data tranSfer), the next Colll>are operation will start on the following block. The Initiator may re-quest sense information (Block Counter) to check the actual num-ber of compared blocks.
WRITE If the command is aborted immediately after a data transfer (ATN must be asserted during the data transfer), all received data will be written to the tape. The Initiator may request sense Information (Block Counter) to check the actual number of blocks written.
WRITE BUFFER This command will be aborted after the last data transfer~ The transferred data has already been written into the data buffer.
Table: Non-overlapped ABORT Message Handling
6-70 SCSl-2 Functional Specifications
(
..(.~ \
I Comm~nd
ERASE
LOADIUNLOAD
READ
READ BUFFER
The following table describes ABORT-handling in overlapped command situations.
I
ActionIn most cases the abortion will immediately bring the Drive to the BUS FREE phase. The tape movement will, however, continue until its normal completion.
In most cases the abortion will immediately bring the Drive to the BUS FREE phase. The tape movement will, however, continue until its normal completion.
In most cases this command will be aborted immediately. Note, however, that while seeking the reference burst (when starting a READ operation on a new cartridge), the command will not abort until the reference burst has been found and the tape format has been determined. The Initiator may resume the READ operation by issuing a new READ command.
This command will be aborted immediately.
RECOVER BUFFERED DATA This command will be aborted immediately.
REWIND _ In most cases the abortion will immediately bring the Drive to the BUS FREE phase. The tape movement will, however, continue until its normal completion.
VERIFY In most cases this command will be aborted immediately. Note, however, that while seeking the reference burst (when starting a READ operation on a new cartridge), the command will not abort until the reference burst has been found and the tape format has been determined. The Initiator may resume the VERIFY operation by issuing a new VERIFY command.
WRITE In most cases this command will be aborted immediately. The Initiator may resume the WRITE operation by issuing a new WRITE command.
WRITE BUFFER This command will be aborted immediately
WRITE FILEMARKS In most cases this command will be aborted immediately. The Initiator may resume the WRITE FILEMARK operation by issuing a new WRITE FILEMARKS command.
Table: Overlapped ABORT Message Handling
6-71 SCSI-2 Functional Specifications
Tandberg Data Message System
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6-72 SCSI-2 Functional Specifications
7.
How to Interpret the Error Code Table