Commands (See ANSI SCSI-2 7)

A command is communicated by sending a command descriptor block to the target. For several commands, the command descriptor block is accompanied by a list of parameters sent during the DATA OUT phase. The command descriptor block always has an operation code as its first byte and a control byte as its last byte.

Reserved (See ANSI SCSI-2 7.1.1)

INTERFACE

 

Reserved bits, fields, bytes, and code values are set aside for future standardization. Their use and interpretation may be specified by future extensions to ANSI SCSI standard. A reserved bit, field, or byte shall be set to zero, or in accordance with a future extension to this standard. A target that receives a reserved bit, field, or byte that is not zero or receives a reserved code value shall terminate the command with CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST.

Logical Unit Number

The logical unit number is defined in the IDENTIFY message. The target shall ignore the logical unit number specified within the command descriptor block if an IDENTIFY message was received. This scanner supports Logical Unit Number 000b only. Followings shows target’s response to selection of invalid logical unit.

In response to an INQUIRY command, the target shall return the INQUIRY data with the peripheral qualifier set to the value required.

In response to any other command except REQUEST SENSE, the target shall terminate the command with CHECK CONDITION status.

In response to an REQUEST SENSE command, the target shall return sense data. The sense key shall be set to ILLEGAL REQUEST and the additional sense code shall be set to

LOGICAL UNIT NOT SUPPORTED.

M3099GX/GH OEM Manual

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