M2488 PRODUCT GUIDE TAPE UNIT SCSI COMMANDS
April 1997 CG00000-011503 REV. A 4-29
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.
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.
Table 4-26. Block ID Format
BITS
BYTES 7 6 5 4 3 2 1 0
0Wrap Physical Reference
1Format Code Logical Block Position (MSB)
2Logical Block Position (middle significant bits)
3Logical Block Position (LSB)
Table 4-25. LOCATE Field Description (Continued)
BYTE BIT VALUE DESCRIPTION