Quantum DAT 24 Drive Betriebsanweisung PDF herunterladen (Seite 31)

SCSI Interface Description Page 19

The following table lists SCSI messages and their definitions.

Hex

Code

Message

Definition

00h

Command

Complete

This message is sent from the drive to inform an Initiator

that execution of a command terminated and that valid

status was sent to the Initiator. After successfully sending

this message, the drive goes to the Bus Free Phase by

releasing BSY.

NOTE: The command may have been executed

successfully or unsuccessfully as indicated in the status.

02h

Save Data

Pointer

This message is sent from the drive to direct the Initiator to

save a copy of the present active data pointer for the drive.

04h

Disconnect This message is sent from the drive to inform an Initiator

that the present physical path is going to be broken (DAT

drive plans to disconnect by releasing BSY) and, a later

reconnect is required to complete the current operation. If

the Initiator detects the Bus Free Phase, other than as the

result of a Reset condition, without first receiving a

Disconnect or Command Complete message, the Initiator

considers this as a catastrophic error condition. The

Disconnect message does not cause the Initiator to save

the data pointer. If Disconnect messages are used to break

a long data transfer into two or more shorter transfers, then

a Save Data Pointer message is issued by the DAT drive

before each Disconnect.

05h

Initiator

Detected

Error

This message is sent from an Initiator to inform the DAT

drive that an error, such as a parity error, occurred.

06h

Abort This message is sent from an Initiator to clear the present

drive operation. All pending data and status for the issuing

Initiator are cleared, and the drive goes back to Bus Free

Phase. No status or ending message is sent for the

operation. Any previously set modes are not changed.

07h

Message

Reject

This message is sent from the DAT drive to indicate the

last message it received was inappropriate or was not

implemented. The DAT drive sends Message Reject and

then goes to the Message-In phase prior to requesting

additional message bytes from the Initiator. This sequence

provides an interlock so the Initiator can determine which

message was rejected.

08h

Operation

This message is sent from an Initiator in response to a DAT

drive request for a message, when the Initiator does not

currently have any other valid message to send.

09h

Parity Error This message is sent from the host to indicate that

incorrect parity was detected. See the following table.

0Ah

Linked

Command

Complete

This message is sent from the DAT drive to inform an

Initiator that execution of a linked command is completed

and that status was sent. The Initiator can then set the

pointers to the initial state for the next linked command.

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