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Messages

Quantum DLT 8000 Tape System 4-5

4.2 Supported SCSI Messages

Following are descriptions of each of the messages supported by the drive.

4.2.1 ABORT Message (06h)

This message is sent from the initiator to the target to clear the current I/O process on

the selected unit. Buffered (cached) write operations are completed if possible. The target

goes directly to the BUS FREE phase after successful receipt of this message. Current

settings of MODE SELECT parameters and reservations are not affected. Commands,

data, and status for other initiators is not affected.

This message can be sent to a logical unit that is not currently performing an operation

for the initiator. If no unit has been selected, the target goes to BUS FREE phase and no

commands, data, or status on the target are affected.

4.2.2 BUS DEVICE RESET Message (0Ch)

The BUS DEVICE RESET message is sent from an initiator to direct the drive to clear all

I/O processes on the drive. The message causes the drive to:

1. Flush the contents of cache to tape and go to the BUS FREE phase.

2. Execute a hard reset, leaving it as if a Bus Reset had occurred.

The drive creates a Unit Attention condition for all initiators after accepting and

processing a Bus Device Reset message. The additional sense code is set to POWER ON,

RESET, or BUS DEVICE RESET OCCURRED.

4.2.3 COMMAND COMPLETE Message (00h)

The COMMAND COMPLETE message is sent by the drive to an initiator to indicate

that an I/O process has completed and that valid status has been sent to the initiator.

After successfully sending this message, the drive goes to the BUS FREE phase by

releasing the BSY signal. The drive considers the message transmission successful when

it detects the negation of ACK for the COMMAND COMPLETE message with the ATN

signal false. If a COMMAND COMPLETE message is received by the tape drive, it is

handled as an illegal message: the drive returns MESSAGE REJECT and enters its

STATUS phase, reporting CHECK CONDITION with the sense key set to COMMAND

ABORTED.

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Quantum DLT 8000 Manual Pagina 135