HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 34

SCSI Command Overview Library Control Commands Save Data Pointer 02H, The target sends this message to the initiator to direct it to save a copy of the present active data pointer for the currently attached logical unit. The target issues this message when it disconnects the SCSI Bus during data transfer, but not if it intends to move directly to the Status phase. When received as a target, it switches to Message In phase and returns MESSAGE REJECT. Restore Pointers 03H, The target sends this message to the initiator so that it will restore the most recently saved pointers (for the currently attached logical unit) as follows: 1. Command, data, and status pointers for the logical unit once again become active. 2. Command and Status pointers go to the beginning of the present Command and Status areas. 3. 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 last SAVE DATA POINTER message that 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. Disconnect 04H, A target sends a DISCONNECT message to tell an initiator that it wants to release control of the SCSI bus (the target intends to disconnect by releasing BSY). To later complete this operation, SCSI bus reselection is required. This message does not cause the initiator to save the data pointer. 1- 10 Chapter 1