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Maxtor Atlas 10K V 5-1
Chapter 5
SCSI Description
This chapter contains an overview of SCSI command and status processing and a
detailed description of the commands supported by the disk drives. The SCSI
command system enables the initiator to instruct the drive to perform specific
functions.
In this manual, unless otherwise stated, numerical values are given in decimal.
Hexadecimal numbers, such as opcodes, are always given with an “h” following, as in
5Ah except when entire data tables are in hexadecimal.
5.1 Overview of the SCSI Command Descriptions
The disk drives support the SCSI-3 commands listed in Table 5-1. The command
categories are sequential, normal, and immediate.
Immediate commands are processed when received by the drive. In most cases, these
commands do not require drive resources, do not change the state of the drive, and
bypass the command queue (unless the command is tagged).
Sequential commands execute in the order that they arrive (unless accompanied by
a HEAD OF QUEUE tag) and execute to completion before a subsequent command
is activated.
Normal commands are allowed to execute concurrently (with the restriction that the
drive executes overlapping writes in the order received). Normal commands are
usually I/O commands
Table 5-1 Supported SCSI Commands
Command Operation Code Category
CHANGE DEFINITION 40h Sequential
FORMAT UNIT 04h Sequential
INQUIRY 12h Immediate
LOG SELECT 4Ch Sequential
LOG SENSE 4Dh Sequential
MODE SELECT (6) 15h Sequential
MODE SELECT (10) 55h Sequential
MODE SENSE (6) 1Ah Sequential
MODE SENSE (10) 5Ah Sequential
PERSISTENT RESERVATION IN 5Eh Sequential