ANSI INCITS-375-2004 pdf download Information Technology – Serial Bus Protocol (SBP-3)
3 Definitions and notation
3.1 Definitions
3.1.1 Conformance
Several keywords are used to differentiate levels of requirements and optionality, as follows:
3.1.1.1 expected: A keyword used to describe the behavior of the hardware or software in the design models assumed by this standard. Other hardware and software design models may also be implemented.
3.1.1.2 ignored: A keyword that describes bits, bytes, quadlets, octlets or fields whose values are not checked by the recipient.
3.1.1.3 may: A keyword that indicates flexibility of choice with no implied preference.
3.1.1.4 reserved: A keyword used to describe objects (bits, bytes, quadlets, octlets and fields) or the code values assigned to these objects in cases where either the object or the code value is set aside for future standardization. Usage and interpretation may be specified by future extensions to this or other standards. A reserved object shall be zeroed or, upon development of a future standard, set to a value specified by such a standard. The recipient of a reserved object shall ignore its value. The recipient of an object defined by this standard as other than reserved shall inspect its value and reject reserved code values.
3.1.1.5 shall: A keyword that indicates a mandatory requirement. Designers are required to implement all such mandatory requirements to assure interoperability with other products conforming to this standard.
3.1.1.6 should: A keyword that denotes flexibility of choice with a strongly preferred alternative. Equivalent to the phrase “is recommended.”
3.1.2 Glossary The following terms are used in this standard:
3.1.2.1 byte: Eight bits of data.
3.1.2.2 command block: Space reserved within an operation request block to describe a command intended for a logical unit that controls device functions or the transfer of data to or from device medium. The format and meaning of command blocks are outside of the scope of SBP-3 and are command set- or device-dependent.
3.1.2.3 device server: A component of a logical unit responsible to execute tasks initiated by command blocks that specify data transfer or other device operations.
3.1.2.4 global node ID: A 16-bit address that may be used as the destination_ID in an asynchronous primary packet so long as the packet passes through at least one bridge portal en route to its destination. The value of the most significant 10 bits, the bus ID, ranges between zero and 3FE 16 , inclusive. Within a net, a bus ID in this range uniquely identifies a single bus. The least significant six bits of a global node ID, the virtual ID, uniquely identify a node on a particular bus.