scope:

1 Scope This standard defines a set of SCSI command descriptor blocks that are useful in accessing and controlling devices with a peripheral device type set to 5. This command set is transport independent and may be implemented across a wide variety of environments for which a SCSI transport protocol has been defined. To date, these include Parallel SCSI, ATA/ATAPI, Serial ATA, Universal Serial Bus (USB versions 1.1 and 2.0), and High Performance Serial Bus (IEEE 1394, 1394A, and 1394B). The command set described has been selected for correct operation when the physical interface is ATA with the ATAPI command protocol. Although some commands are also described in the SPC-3, the descriptions are also in this standard for the purpose of profiling mandatory and optional command features as applied to multimedia devices. The objective of this command set is to provide for the following: 

• A definition of the command formats and functions independent of delivery, protocol/signaling or transport mechanism. Architectural constraints regarding command functions, over the various transports, are addressed in the document specific to the physical transport. 
• Standardized access to common features of devices employed in multimedia applications. 
• System software/firmware independence across device classes and physical interfaces. Provision is made for the addition of special features and functions through the use of vendorspecific options.
• Compatibility such that properly conforming devices may interoperate with subsequent devices.