Date: 19 April 1991                   X3T9.2/91-53 Rev 0 
                 
                 
                To:   John Lohmeyer
                      Chairman, ANSI X3T9.2 (SCSI)
                 
                From: Doug Hagerman
                      Digital Equipment Corporation
                      SHR 1-3/E29
                      333 South Street
                      Shrewsbury, MA  01545
                      Phone: 508-841-2145  FAX: 508-841-2604
                 
                Subject:  Various SCSI Interpretation Questions
 
 
 
 
        1  QUESTION STATEMENT
 
        Would it be possible to obtain clarification on the following
        questions related to interpreting the ANSI SCSI Standard?
 
 
 
        2  RE.  5.6.3 BUS DEVICE RESET.
 
        In the case of an initiator acting as a target, does receipt
        of a BDR cause ALL processes to be cleared or only those
        processes being handled in the target role?
 
 
 
        3  RE.  6.7 EXTENDED CONTINGENT ALLEGIANCE CONDITION AND
           5.6.17 QUEUE TAG MESSAGES.
 
        What is the priority of command validation?  In the case of a
        pending ECA, commands from all other initiators are to be
        returned with BUSY status (6.7).  However, if another
        initiator reconnects to a tagged I/O process using an invalid
        tag, the target is to validate the queue tag and return an
        ABORT TAG message (5.6.17).  Which is it:  BUSY status or
        ABORT TAG message?
 
 
 
        4  RE.  6.7 EXTENDED CONTINGENT ALLEGIANCE CONDITION.
 
        While the ECA condition exists the target shall respond to any
        other request for access to the logical unit from another

 
 
 
 
 
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        initiator with BUSY status.  Does "access to the logical unit"
        mean data transfer requests or is it ok to respond to
        non-media requests from another initiator even though an ECA
        exists?
 
 
 
        5  8.2.8 READ DEFECT DATA COMMAND
 
        The two-byte Defect List Length field only allows for 8k
        defect descriptors, which may not be enough for future
        devices.
 
 
 
        6  8.3.3.3 FORMAT DEVICE PAGE
 
        Does Data Bytes per Physical Sector include any ECC bytes?  If
        the device has 512 data bytes per logical block and say 7 ECC
        bytes, is the Data Bytes per Physical Sector number 519?
 
 
 
        7  13.2.10 READ SUB-CHANNEL COMMAND
 
        Is it ok to optionally implement only part of an optional
        command?  For example, in the READ SUB-CHANNEL command, the
        Sub-channel Data Format field is used to specify the returned
        Sub Channel Data.  Is it valid for a device to properly return
        data when values 01h, 02h, and 03h are requested, but if 00h
        is requested to reject the command, returning a CHECK
        CONDITION status with an ILLEGAL REQUEST/INVALID FIELD IN CDB
        sense key?
 
 
 
        8  5.4 SCSI POINTERS
 
        In consideration of the ability for a single initiator to have
        multiple active I/O processes in one target, the wording of
        the last paragraph of this section appears incorrect, as it
        implies that only one process is active.