No Operation (08H); Restore Pointers Message (03H); Save Data Pointer Message (02H) - Quantum DLT 8000 Product Manual

Messages

4.2.12 NO OPERATION (08h)

If a target requests a message, the initiator sends a NO OPERATION message if it does
not currently have any other valid message to send. The message is accepted when the
drive is acting as a target and may be sent when it is an initiator. If a NO OPERATION
message is received during a selection, the drive proceeds to the COMMAND phase
(provided ATN does not continue as asserted); the NO OPERATION message is ignored
by the tape drive.

4.2.13 RESTORE POINTERS Message (03h)

The RESTORE POINTERS message is sent from the drive to the initiator to direct the
initiator to copy the most recently saved command, data, and status pointers for the I/O
process to the corresponding current pointers. The command and status pointers are
restored to the beginning of the present command and status areas. The data pointer is
restored to the value at the beginning of the data area in the absence of a SAVE DATA
POINTER message or to the value at the point at which the last SAVE DATA
POINTER message occurred for that logical unit.
When the RESTORE POINTERS message is received as a target, the target switches to
the message in phase and returns MESSAGE REJECT.

4.2.14 SAVE DATA POINTER Message (02h)

The SAVE DATA POINTER message is sent from the drive to direct the initiator to copy
the current data pointer to the saved data pointer for the current I/O processes.
When functioning as a target, the tape drive sends this message before a disconnect
during a data transfer. It does not send a SAVE DATA POINTER message if it intends
to move directly to STATUS phase. When received as a target, it switches to message in
phase and returns MESSAGE REJECT.
Quantum DLT 8000 Tape System 4-11