Optical Drive and Library SCSI-2 Command Reference

SCSI-2 Drive Command Set
Pre-Fetch (34H)
Chapter 22-94
Pre-Fetch (34H)
The Pre-Fetch command is used to transfer the specified number of data
blocks starting from the specified logical block address to cache memory.
Immed An Immediate bit of 1 indicates that the drive returns a
status as soon as the command descriptor block is
validated.
An Immed bit of 0 indicates that the status is not
returned until the operation is completed.
Transfer
Length This field indicates the number of contiguous logical
blocks of data to be transferred.
Rel Adr A relative address bit of one indicates that logical block
address specified is a two’s complement offset from the
last logical block address accessed.
A value of 0 indicates that the logical block address is an
absolute address.
Table 2-81 Pre-Fetch Command
Byte 7 6 5 4 3 2 1 0
0 Operation Code (34H)
1 Reserved (0) Immed RelAdr
2 Logical Block Address (MSByte)
3 Logical Block Address
4 Logical Block Address
5 Logical Block Address (LSByte)
6 Reserved (0)
7 Transfer Length (MSByte)
8 Transfer Length (LSByte)
9 Reserved (0) Flag Link