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SDLT 600 SCSI Interface Guide Chapter 3: SCSI Messages

81-81200-02 REV A01 January 2005 3-5

3.2.2 TARGET RESET (0Ch)

An initiator sends the TARGET RESET message to direct the SDLT tape drive to clear all I/O

processes. This message causes the drive to:

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

2. Execute a soft reset, leaving the drive as if a Bus Reset had occurred.

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

RESET message. The additional sense code is set to TARGET RESET OCCURRED.

If a WRITE command is in progress and STATUS has not been sent to the initiator when the drive

receives this message, the drive may write some or all of the data for the WRITE command to the

medium.

3.2.3 TASK COMPLETE (00h)

The SDLT tape drive sends the TASK COMPLETE message to an initiator to indicate that an I/O

process has completed and that the drive sent VALID STATUS to the initiator. After successfully

sending this message, the drive enters 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 TASK

COMPLETE message with the ATN signal false. If the SDLT tape drive receives the TASK

COMPLETE message, the drive handles it as an illegal message, returning MESSAGE REJECT.

3.2.4 DISCONNECT (04h)

The SDLT tape drive sends the DISCONNECT message to inform the initiator that the drive is about

to break the present connection by releasing the BSY signal and that a later reconnect is required to

complete the current I/O process. The message does not cause the initiator to save the data pointer.

After sending the message, the drive enters the BUS FREE phase by releasing the BSY signal.

The initiator may also send the DISCONNECT message to tell the drive to suspend the current phase

and disconnect from the bus. The drive’s response to and its handling of a DISCONNECT message are

based on when, in the I/O process, the initiator sends the DISCONNECT message. Table 3-4

summarizes the drive’s response.

Table 3-4. Drive’s Response to DISCONNECT Message

BUS Phase Drive Response

SELECTION The drive discards the DISCONNECT message and enters the BUS FREE

phase.

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 293 294

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