Keywords; Physical Interface Characteristics - Seagate SCSI Interface Product Manual

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unlinked command—A SCSI-3 command having the link bit set to zero in the CDB control byte.
upper level protocol—An application-specific protocol executed through services provided by a lower level
protocol.
1.2.2

Keywords

Several keywords are used to differentiate between different levels of requirements and optionality, as follows:
vendor-specific—Specification of the referenced item is determined by the device vendor.
protocol-specific—Implementation of the referenced item is defined by a SCSI-3 protocol standard (see Sec-
tion 1.1.1.)
expected—A keyword used to describe the behavior of the models specified by this standard.
mandatory—A keyword indicating items required to be implemented as defined by this standard.
may—A keyword that indicates flexibility of choice with no implied preference.
obsolete—A keyword indicating items that were defined in prior SCSI standards but have been removed from
this standard.
option, optional—Keywords that describe features which are not required to be implemented by this standard.
However, if any optional feature defined by the standard is implemented, it shall be implemented as defined by
the standard.
reserved—A key word referring to bits, bytes, words, fields, and code values that are set aside for future stan-
dardization. Their use and interpretation may be specified by the future extensions to this or other standards. A
reserved bit, byte, word, or field shall be set to zero, or in accordance with a future extension to this standard.
The recipient shall not check reserved bits, bytes, words, or fields. Receipt of reserved code values in defined
fields shall be treated as an error.
shall—A keyword indicating a mandatory requirement. Designers are required to implement all such manda-
tory requirements to ensure interoperability with other standard conformant products.
should—A keyword indicating flexibility of choice with a strongly preferred alternative. Equivalent to the phrase
"it is recommended."
1.3

Physical interface characteristics

The physical interface characteristics (cables, connectors, electrical descriptions, termination requirements,
etc.) for the drives covered by this Interface Manual are found in each individual drive's Product Manual, Vol-
ume 1, since these features are not the same for all drives.
SCSI Interface Product Manual, Rev. J