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.
5.1Overview of the SCSI Command Descriptions
The disk drives support the
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
Command | Operation Code | Category |
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CHANGE DEFINITION | 40h | Sequential |
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FORMAT UNIT | 04h | Sequential |
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INQUIRY | 12h | Immediate |
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LOG SELECT | 4Ch | Sequential |
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LOG SENSE | 4Dh | Sequential |
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MODE SELECT (6) | 15h | Sequential |
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MODE SELECT (10) | 55h | Sequential |
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MODE SENSE (6) | 1Ah | Sequential |
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MODE SENSE (10) | 5Ah | Sequential |
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PERSISTENT RESERVATION IN | 5Eh | Sequential |
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Maxtor Atlas 10K V |