Quantum ATL PowerStor L200 Series, User Manual

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Chapter 4 SCSI Interface
SCSI Message System
ATL PowerStor L200 Series Library User’s Guide 59
03h - Wide Data Transfer Request
04h-7Fh - Reserved
80-FFh - Vendor Unique
If the library receives an extended message which it does not support,
it switches to message in phase and returns
MESSAGE REJECT
after all
the bytes of the message have been transferred.
Identify (80h-FFh)
4
These messages are sent either by the initiator or by the target to
establish (or reestablish) the physical connection path between an
initiator and target for a particular logical unit. The message byte
consists of the following bits:
• Bit 7: always set to one.
•
Bit 6: set by initiator if target is allowed to disconnect/reconnect
•
Bit 5: must be set to zero ("Target Routines" not supported)
•
Bit 4: reserved, must be set to zero
• Bit 3: reserved, must be set to zero
•
Bits 2-0: logical unit number (LUN)
When the Identify message is sent from a target to an initiator during
reconnection, a
RESTORE POINTERS
message is implied.
Initiator Detected
Error (05h)
4
This message is sent from an initiator to inform a target that an error
(for example, a bus parity error) has occurred that does not prevent the
target from trying the operation again. When received, the library
attempts to retransfer the last command, data, or status bytes by using
the
RESTORE POINTERS
message mechanism.
Linked Command
Complete (0Ah)
4
This message is sent from a target to an initiator to indicate that the
execution of a linked command (with the Flag bit zero) is complete and
that status has been sent. The initiator then sets the pointers to the
initial state for the next command.
When received as a target, it is handled as an illegal message; the
library enters the
MESSAGE IN
phase and returns
MESSAGE REJECT
.
Linked Command
Complete, with flag
(0Bh)
4
This message is sent from a target to an initiator to indicate that the
execution of a linked command (with the Flag bit set to one) is
complete and that status has been sent.