HP Surestore 80fx Optical Drive and Library SCSI-2 Command Reference - Page 35

SCSI Command Overview Drive Control Commands Conditions Attention Condition The Attention Condition allows an initiator to inform the target that the initiator has a message ready. The target gets this message at its convenience by performing a Message Out Phase as follows: 1. If the ATN signal becomes true during a COMMAND phase, the drive enters the MESSAGE OUT phase after transferring part or all of the command descriptor block bytes. 2. If the ATN signal becomes true during a DATA phase, the drive enters the MESSAGE OUT phase at the drives earliest convenience. The initiator will continue REQ/ACK handshakes until it detects the phase change. 3. If the ATN signal becomes true during a STATUS phase, the drive enters the MESSAGE OUT phase after the status byte has been acknowledged by the initiator. 4. If the ATN signal becomes true during a MESSAGE IN phase, the drive enters the MESSAGE OUT phase before it sends another message. 5. If the ATN signal becomes true during a SELECTION phase and before the initiator releases the BSY signal, the drive enters the MESSAGE OUT phase immediately after that SELECTION phase. 6. If the ATN signal becomes true during a RESELECTION phase, the drive enters the MESSAGE OUT phase after sending its IDENTIFY message for that RESELECTION phase. Reset Condition The drive implements the hard reset alternative, upon detection of the RESET condition. When the drive creates the reset conditions, it clears all I/O processes including queued I/O processes, releases all reservations, returns any SCSI device operating modes (MODE SELECT, PREVENT/ALLOW MEDIUM REMOVAL commands, etc.) to their initial conditions, and generates UNIT ATTENTION condition. 1-16 Chapter 1