User's Manual

DLT4000 SCSI Interface
8-6 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem
These commands are as follows:
• INQUIRY
• LOAD UNLOAD
• LOG SENSE/SELECT
• MODE SELECT
• MODE SENSE
• PREVENT/ALLOW MEDIUM REMOVAL
• READ BLOCK LIMITS
• READ BUFFER
• READ ELEMENT STATUS
• RECEIVE DIAGNOSTIC RESULTS
• REQUEST SENSE
• RESERVE/RELEASE UNIT
• SEND DIAGNOSTIC (non-media access diagnostics)
• WRITE BUFFER
The TEST UNIT READY command is used to determine whether the tape drive
would accept a media access command without returning CHECK CONDITION
status.
8.2.11 BUS FREE
There are several situations when the device might or will go to BUS FREE
unexpectedly, as defined in the SCSI-2 standard (See sections 6.1.1 and 6.3):
• An internal hardware or firmware fault that makes it unsafe for the device to
continue operation without a full reset (similar to a power-up reset).
• ATN asserted or bus parity error detected during non-tape data transfers.
8.2.12 BUS PARITY ERRORS
The occurrence of bus parity errors (i.e. single bit errors) are very serious because they
imply the possibility of undetected double-bit errors on the bus, which most likely
would result in undetected data corruption. On properly configured SCSI buses, parity
errors should be extremely rare. If any are detected, they should be quickly addressed