ATA Packet Interface (ATAPI) is a protocol that has been added to
Parallel ATA and
Serial ATA so that a greater variety of devices can be connected to a computer than with the ATA command set alone. It carries
SCSI commands and responses through the ATA interface. ATAPI devices include CD-ROM and
DVD-ROM
The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
drives,
tape drive
A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and a long archival stability.
...
s,
magneto-optical drive
A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. Both 130 mm (5.25 in) and 90 mm (3.5 in) form factors exist. In 1983, just a year after the introduct ...
s, and large-capacity
floppy
A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined wi ...
drives such as the
Zip drive
The Zip drive is a removable floppy disk storage system that was introduced by Iomega in late 1994. Considered medium-to-high-capacity at the time of its release, Zip disks were originally launched with capacities of 100 MB, then 250 ...
and
SuperDisk drive
The SuperDisk LS-120 is a high-speed, high-capacity alternative to the 90 mm (3.5 in), 1.44 MB floppy disk. The SuperDisk hardware was created by 3M's storage products group Imation in 1997, with manufacturing chiefly by ...
.
Background
ATA was originally designed for, and worked only with hard disks and devices that could emulate them. A group called the
Small Form Factor committee
The Small Form Factor Committee (SFF) is an ''ad hoc'' electronics industry group formed to quickly develop interoperability specifications (as a complement to the traditional standards process).
The SFF Committee was formed in 1990 to define the ...
(SFF) introduced ATAPI (ATA Packet Interface) ATA to be used for a variety of other devices that require functions beyond those necessary for hard disks. For example, any removable media device needs a "media eject" command, and a way for the host to determine whether the media is present, and these were not provided in the ATA protocol.
The Small Form Factor committee approached this problem by defining ATAPI, the "ATA Packet Interface," as part of the fourth generation of ATA. ATAPI carries SCSI commands through ATA, so ATAPI devices are "speaking SCSI" other than at the electrical interface. In fact, some early ATAPI devices were simply SCSI devices with an ATA/ATAPI to SCSI protocol converter added on. The SCSI commands and responses are embedded in "packets" (hence "ATA Packet Interface") for transmission on the ATA cable. This interfaces ATA with any device class for which a SCSI command set has been defined. ATAPI devices are also "speaking ATA" because the ATA physical interface and protocol are still being used to send the packets.
The
Direct Memory Access
Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU).
Without DMA, when the CPU is using programmed input/output, it is ...
feature for the ATA interface was introduced along with ATAPI.
Definition
The SCSI commands and responses used by each class of ATAPI device (CD-ROM, tape, etc.) are described in other documents or specifications specific to those device classes and are not within ATA/ATAPI or the
T13 committee's purview. One commonly used set is defined in the
MMC SCSI command set.
ATAPI was adopted as part of ATA in
INCITS 317-1998, ''AT Attachment with Packet Interface Extension (ATA/ATAPI-4)''.
See also
*
SCSI / ATA Translation
SCSI / ATA Translation (SAT) is a set of standards developed by the T10 subcommittee, defining how to communicate with ATA devices through a SCSI application layer. The standard attempts to be consistent with the SCSI architectural model, the ...
(SAT)
References
External links
* {{cite web , last1=Necasek , first1=Michal , title=The Secret History of ATAPI , url=https://www.os2museum.com/wp/the-secret-history-of-atapi/ , website=OS/2 Museum , access-date=25 November 2021 , date=24 November 2021
Communications protocols
AT Attachment
SCSI