SCSI Protocol

SCSI Protocol

Separate protocols exist for the tape library and the tape drive.
The sections that follow describe the protocol for each.

Protocol for Tape Library

The tape library uses SCSI-2 protocol to communicate with the host computer.
It communicates as a medium changer device, and is available in both differential and single-ended versions.
The tape library is a single device target that does not support multiple logical units.
Each tape library occupies a maximum of three SCSI target IDs: two for the drives and one for the robotics.
The tape library does not support linked commands, tagged command queuing, or the flag bit.
Also, the tape library controller does not initiate negotiation of Transfer Parameters.
It does, however, participate in (or respond to) negotiations from the host.
The tape library defaults to and only supports asynchronous (slow) and narrow transfer parameters.

The software for the tape library robotics is completely self-contained and executes commands received from the host over the SCSI bus.
Error recovery is transparent to the host. To support high reliability Systems, the tape library can report its internal voltages, drive temperatures, and the controller temperature as log sense information that can be sent to the host computer.

Protocol for Tape Drive

The DLT7000 drive supports wide and narrow asynchronous and synchronous data transfers.
The product has differential and single-ended versions. Odd parity is generated during all information transfer phases where the drive writes data to the SCSI bus.
Parity is checked during all information transfer phases where data are read from the bus. Parity checking can be disabled.
For information about changing parity, contact your support personnel.

The DLT7000 drive supports a block size of from 1 byte to 16 MB (where MB equals one megabyte or 1 000 000 bytes).

Disconnections from the SCSI bus are done at regular intervals during a data transfer.
This allows other devices to access the bus.

The DLT7000 drive does not act as an initiator on the SCSI bus.

Therefore, the drive does not:

Other SCSI functions that are supported include linked commands and untagged queuing.

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