Fujitsu M2488 manual Locate Field Description, Block ID Format

M2488 PRODUCT GUIDE TAPE UNIT SCSI COMMANDS

		Table 4-25.	LOCATE Field Description (Continued)
BYTE	BIT	VALUE		DESCRIPTION
1	2		0	The Block Address Type (BT) is interpreted as a logical block address.
				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 3FFEFFh.
			1	The Block address is interpreted as a device specific block address. For
				this tape unit these addresses are also known as Block IDs. The Block ID
				consists of four fields: Wrap, Physical reference, Format code and Logical
				block position. The format of a Block ID is shown in Table 4-26.
3-6				Block Address
8				The Partition field specifies the target position.

The high speed locate is at 4 meters per second. High speed positioning will not occur if the Block Address Type (BT) bit is 0. It will also not occur if the BT bit is 1 and the Wrap and Physical ref- erence fields of the Block address are both 0.

Table 4-26. Block ID Format

						BITS
BYTES	7	6	5		4		3	2	1	0
0	Wrap					Physical Reference
1	Format Code					Logical Block Position (MSB)
2			Logical Block Position (middle significant bits)
3				Logical Block Position (LSB)

April 1997 CG00000-011503 REV. A 4-29