scsi interface specification - Plasmon

GENERAL DESCRIPTIONGENERAL DESCRIPTIONThe Small Computer System Interface (SCSI) standard defines an input/output bus for interconnectingcomputers and peripheral devices. SCSI is a local I/O bus that can be operated over a wide range of datarates. The primary objective of SCSI is to provide system integrators with an easy to use, reliable, industrystandardperipheral device interface. Other objectives include provision for device independence andinteroperability and to move device-dependent intelligence out to the peripherals.NOTEThe word "LaserDrive", as used in this document, refers to theLD 6100, the LF 6600 and the LF 6602. If a feature appliesspecifically to a configuration, then the appropriate model number isused.The interface uses logical rather than physical addressing for all data blocks. The LaserDrive implementsSCSI commands that facilitate the writing of self-configuring software drivers that can "discover" allnecessary attributes without prior knowledge of specific peripheral characteristics (such as storagecapacity).The SCSI protocols include provisions for the connection of multiple initiators and multiple targets. SCSIbus arbitration is supported by the LaserDrive.SCSI defines a message protocol for control of the interface. These messages allow the peripherals andthe host adapters to manage the use of the SCSI bus. In most cases, messages are not directly apparentto the host computer software.There are two electrical interface alternatives: single ended and differential. Single-ended and differentialdevices are electrically different and cannot be mixed on the same bus. The single-ended configurationsupports cable lengths of up to 6 m (19.5 ft). The differential driver option supports cable lengths of up to25 m (82 ft).NOTEPlasmon LMS does not recommend single-ended fast synchronous.The LaserDrive implements all mandatory and extended set commands in the American NationalStandards Institute (ANSI) Small Computer Systems Interface (SCSI-2), specification X3.131-1994,defined for write once read many times (WORM) devices and many of the optional commands. TheLaserDrive supports one Logical Unit Number (LUN) - LUN 0 only - on the SCSI bus.SCSI Bus Parity generation is always performed and parity checking is selectable. This device implementsthe "hard" reset option. Reservation queuing is not supported.The LF 6600 and LF 6602 implement all of the commands implemented by the LD 6100. Additionally, theLF 6600 and LF 6602 implement commands which control and report status of the shuttle. Theseadditions are noted throughout this document.97653978 HPage 7