HP Surestore 80fx Optical Drive and Library SCSI-2 Command Reference - Page 22

SCSI Command Overview SCSI Command Overview Drive Control Commands Drive Control Commands This section describes all specifications, except command specifications of the target. The "SCSI Commands Used by the Target" are described later in this chapter. SCSI Bus Phases The target supports the following phases specified in the SCSI standard. Arbitration phase When the drive tries to reconnect to an initiator to continue command operations, it waits for the BUS FREE phase, then enters the ARBITRATION phase. Selection phase The selection phase allows an initiator to select a target for the purpose of initiating a target function such as a read or write command. During the selection phase the I/O signal is negated so that this phase can be distinguished from the reselection phase. The drive examines the DATA BUS to determine the selecting initiator SCSI ID. If it cannot detect the ID, the drive does not respond to the selection. Reselection phase The reselection phase allows the target to reconnect to an initiator to continue the command started by the initiator, but suspended by the target. Information transfer phase The command, data, status, and message phases are all grouped together as the information transfer phases because they are all used to transfer data or control information via the data bus. Chapter 1 1-3