270 SCSI Guide
Target Operation
The Scalar 1000 and Scalar 10K library target respond to control information or data from the host. The
library does not:
• Generate unsolicited interrupts to the host
• Initiate its own SCSI commands
• Assert bus resets
Element Addressing
The host references source and target designations with element addresses within the library. Each
element within the library has a unique address. The element addresses are established according to the
firmware version of the library.
The Scalar 1000 has two firmware versions:
• Firmware earlier than Version 3.0
• Firmware Version 3.0
The addressing scheme of the Scalar 1000 depends on the firmware version that is used.
The Scalar 10K SCSI addressing scheme is:
• One Cartridge Accessor exists. Its assigned address is always 1h.
• The I/E station locations are addressed continuously from top to bottom, station by station.
• Tape drive locations are addressed from lower left to upper right, rack by rack.
• Storage element locations are addressed from the top left to lower right, column by column, rack by
rack.
SCSI Communications
Scalar 1000 and Scalar 10K communications are implemented across the SCSI bus. The following
paragraphs discuss the bus phases.
Bus Phases
The Scalar 1000 and Scalar 10K conforms to the bus state transition table of the SCSI-2 standard, Phase
Sequences. Bus phases determine the type of information and direction on the interface as shown in table
below.
Phase Description
Bus Free The Bus Free phase indicates that the bus is idle.
Arbitration The Arbitration phase allows devices to compete for bus access.
Selection The Selection phase allows the host initiator to select the target destination for
communication.
Reselection The Reselection phase allows the target to reconnect to the host initiator after a
disconnect has occurred.
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