ATAPI (ATA Packet Interface) is a protocol used with the
Parallel ATA
Parallel ATA (PATA), originally , also known as Integrated Drive Electronics (IDE), is a standard interface designed for IBM PC-compatible computers. It was first developed by Western Digital and Compaq in 1986 for compatible hard drives and C ...
(IDE) and
Serial ATA
SATA (Serial AT Attachment) is a computer bus interface that connects host adapter, host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PAT ...
standards so that a greater variety of devices can be connected to a computer than with the ATA command set alone. It carries
SCSI
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced ...
commands and responses through the ATA interface.
ATAPI devices include CD-ROM and
DVD-ROM 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 long archival stability.
...
s,
magneto-optical drives,
CompactFlash drives, and large-capacity
floppy drives such as the
Zip drive
The Zip drive is a removable floppy disk storage system that was announced by Iomega in 1994 and began shipping in March 1995. Considered medium-to-high-capacity at the time of its release, Zip disks were originally launched with capacities ...
and
SuperDisk drive.
History
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 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 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 that allows certain hardware subsystems to access main system computer memory, memory independently of the central processing unit (CPU).
Without DMA, when the CPU is using programmed i ...
feature for the ATA interface was introduced along with ATAPI.
Specification
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
*
References
External links
* {{ cite web , last = Necasek , first = 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