Tandberg Data VXA-320 (VXA-3) manual Bus Phase, Description, Transfer, Scsi Message System

	SCSI COMMUNICATION INTERFACE
Table 6-1SCSI bus phases and information transfer phases
Bus Phase	Description
Transfer:	The Message phases help manage the physical path between the initiators and targets.

ƒMessage In/ ƒ In the Message In phase, the tape drive sends a message to the initiator. In the Message

Message Out Out phase, the initiator sends a message to the tape drive.

ƒCommand ƒ In the Command Out phase, the initiator sends a command to the tape drive.

Out Commands contain information about what actions the tape drive should perform.

ƒData In/ ƒ In the Data In phase, the tape drive transfers data to the initiator. In the Data Out

Data Out phase, the initiator transfers data to the tape drive.

ƒStatus In ƒ In the Status In phase, the tape drive returns a status byte to the initiator. The status byte indicates the results of the command’s execution.

SCSI MESSAGE SYSTEM

The SCSI message system allows communication between a SCSI initiator and the VXA-320 tape drive for interface management. This message system or command set is separate from the SCSI command protocol used to control the operation of the tape drive. A message can be one byte or multiple bytes. Table 6-2describes the SCSI messages that the tape drive supports.

Table 6-2SCSI messages supported by the tape drive

Message	Hex	Description
	Code
Task	00h	The tape drive informs the initiator that the execution of the command was
Complete		completed and that it sent a valid status byte to the initiator.
Extended	01h	Synchronous Data Transfer Request (01h) The tape drive supports
Messages		synchronous data transfer.
		Wide Data Transfer Request (03h) The tape drive supports wide data transfer.
		Parallel Protocol Request (04h) The tape drive supports negotiating a
		synchronous data transfer agreement, a wide data transfer agreement, and setting
		the protocol options between two SCSI devices.
Save Data	02h	The tape drive requests that the initiator copy the current data pointer for possible
Pointer		use by the Restore Pointers message during error recovery.
Restore	03h	The tape drive informs the initiator that it did not properly receive a block of data
Pointers		or the command descriptor block (CDB) and that the data needs to be transferred
		again.
Disconnect	04h	The tape drive informs the initiator that it plans to disconnect from the SCSI bus
		and that a reconnect will be required later.
Initiator	05h	The initiator informs the tape drive that an error occurred. The tape drive can retry
Detected		the operation.
Error

OCTOBER 2006 VXA-320 TAPE DRIVE

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