Fujitsu M2488 manual Read Position command 34h, 17.1READ Position CDB Description

M2488 PRODUCT GUIDE TAPE UNIT SCSI COMMANDS

4-3.17 READ POSITION command 34h

The READ POSITION command causes 20 bytes to be sent from the target to the initiator. The 20 bytes are a report of the position of the tape unit and information about blocks stored in the buffer; the format of this data is shown in paragraph 4-3.17.2 on page 4-76.

This command can be executed when no tape cartridge is loaded or when the tape unit is not ready. No tape movement is initiated due to this command.

4-3.17.1READ POSITION CDB Description

READ POSITION is a ten-byte command. The bytes are shown below and described in Table 4-

70.Common fields are described in paragraph 4-3.1 on page 4-4.

BITS

BYTES	7	6	5		4		3		2	1		0
0	0	0	1		1		0		1	0		0
1
		LUN						Reserved					BT
2						Reserved
3						Reserved
4						Reserved
5						Reserved
6						Reserved
7						Reserved
8						Reserved
9
				Reserved							Flag		Link

Note: Changeable fields in the CDB are shaded.

Table 4-70. READ POSITION Field Description

BYTE	BIT	VALUE	DESCRIPTION
0	0-7	34h	Operation code.
1	0		The BT bit dictates the format of values reported in the First Block Loca-
			tion and Last Block Location fields of the return data.
		0	Values in First Block Location and Last Block Location are to be reported
			as Logical block addresses. The first filemark or data block on tape is
			assigned logical block address 0; logical block addresses increase by 1 for
			each data block and filemark thereafter. The maximum Logical block
			address is 3FFFEFh.
		1	Values in First Block Location and Last Block Location are to be reported
			as Device specific block addresses (also known as Block IDs). The format
			of these device specific block addresses are shown in paragraph 4-3.17.3
			on page 4-78.

April 1997 CG00000-011503 REV. A 4-75