scsi interface specification - Plasmon

LASER-DRIVE SCSI CHARACTERISTICSMESSAGE SYSTEM SPECIFICATIONMESSAGE PROTOCOLThe LaserDrive implements the mandatory SCSI messages.The first message sent by the Initiator after the SELECTION phase shall be either the IDENTIFY, ABORTor BUS DEVICE RESET message. The IDENTIFY message establishes the physical path for a particularlogical unit specified by the Initiator. After the RESELECTION phase, the LaserDrive's first message isIDENTIFY. This allows the physical path to be re-established for the LaserDrive specified logical unitnumber. Only one logical unit number can be identified for any one selection sequence; a secondIDENTIFY message with a new logical unit number must not be issued before the SCSI bus has beenreleased (BUS FREE phase). The treatment of other logical unit addressing errors is described in theMessages section.All Initiators shall support the mandatory messages as indicated in the "Initiator Support" column of Table 1.The LaserDrive supports messages as indicated in the Sends and Accepts columns of Table 1.Whenever a physical path is established in an Initiator that is utilizing disconnection and reconnection, theInitiator shall ensure that the active pointers of the physical path are equal to the saved pointers for thatparticular logical unit number. An implied restore pointers operation occurs as a result of a reselection.The LaserDrive will respond with a message reject message to messages with a "No" in the Drive Acceptscolumn. Messages that are not applicable "N.A.", are referred to as inappropriate messages. TheLaserDrive will terminate the command and report an Inapplicable/Inappropriate Message Error, if aRequest Sense Command is the next command sense.MESSAGESThe messages supported by the LaserDrive are listed in the following paragraphs along with their codevalues and definitions.Command Complete 00HThis message is sent from the LaserDrive to an Initiator to indicate that the execution of a command hasterminated and that valid status has been sent to the Initiator. After successfully sending this message,the LaserDrive goes to the BUS FREE phase by releasing BSY. The LaserDrive considers the messagetransmission to be successful when it detects the negation of ACK for the COMMAND COMPLETEmessage with the ATTN signal false.NOTEThe command may have been executed successfully orunsuccessfully as indicated in the status.97653978 HPage 11