Quantum DLT 2500, Product Manual

Page: 151 / 345

DLT2000 SCSI Interface
DLT2000/DLT2700 Cartridge Tape Subsystem 8-5
8.2.9 ATTENTION Signal Response
The DLT2000 will respond to an ATN condition at least at every phase transition, as
long as the initiator sets the ATN bit before the target deasserts the REQ for the last
byte of the previous phase. Generally ATN will be recognized immediately by the
DLT2000, and it will change the bus phase to Message Out.
8.2.10 STATUS phase
The DLT2000 will enter the status phase just once per command, unless a retry is
requested by the initiator. The only exception is during error cases when the device
goes immediately to bus free, as defined in the SCSI-2 standard.
Status bytes the tape drive returns are as follows:
•
GOOD (00): This status indicates the drive successfully completed the command.
•
CHECK CONDITION (02): A contingent allegiance condition occurred. The
REQUEST SENSE command should be sent following this status to determine the
nature of the event.
•
BUSY (08): The target is busy. This status is returned whenever the device is
unable to accept a command from an otherwise acceptable initiator. The initiator
should reissue the command at a later time.
•
INTERMEDIATE GOOD (10h): This status is returned instead of GOOD status
for commands issued with the LINK bit set. Following the return of this status, the
drive will proceed to the COMMAND phase for the transfer of the next linked
command.
•
RESERVATION CONFLICT (18h): This status is returned by the drive whenever
a SCSI device attempts to access the drive when it has been reserved for another
initiator with a RESERVE UNIT command.
•
COMMAND TERMINATED (22h): This is the status returned for a command that
was terminated by a TERMINATE I/O PROCESS message. This status also
indicates that a contingent allegiance condition has occurred.