Advanced Technology Attachment Packet Interface (ATAPI)

What is ATAPI (Advanced Technology Attachment Packet Interface)?

ATAPI, or Advanced Technology Attachment Packet Interface refers to the extension of ATA. This is actually the standard IDE/ATA hardware interface for different fixed and removable drives.

Technically, ATAPI is designed to allow SATA and IDE controllers to support optical drives. Typically, ATAPI was adopted as a constituent of the AT Attachment in INCITS 317-1998.

Understanding ATAPI (Advanced Technology Attachment Packet Interface)

What is ATAPI (Advanced Technology Attachment Packet Interface)

ATAPI is an interface standard developed by Western Digital. This interface is supported by the International Committee for Information Technology Standards or INCITS under the name of the Integrated Drive Electronics (IDE) interface.

Advanced Technology Attachment Packet Interface is the protocol that allows connecting a much wider variety of devices and peripherals to a computer than ATA, PATA, IDE and SATA would allow on their own.

To name a few, this particular interface allows connecting the following:

In addition to that, ATAPI is designed typically so that it allows the Serial Advanced Technology Attachment or SATA and IDE controllers to support different optical drives as well. These drives include the following:

Actually, AT Attachment technology does not support the particular functions necessary by the optical drives on its own.

For example, the media eject command or the way in which the controller can figure out whether or not any media is there in the optical drive, are not supported by it.

For this specific purpose, ATAPI needs to use Small Computer System Interface or SCSI commands set in the packets.

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These particular commands help it to support the functions necessary for the removable drives.

However, using ATAPI offers a few significant advantages such as:

Typically, ATAPI also refers to the devices running on command sets of Advanced Technology Attachments or ATA-6 or higher standards, by using the Packet Interface.

This basically signifies the specific way in which SCSI commands are issued to CD-ROM, DVD-ROM and other devices connected to the ATA bus.

Ideally, prior to the launch of ATA-4, ATAPI was considered as an atypical standard from ATA.

Therefore, the design was improved even further over time, and the improved version of the AT Attachment technology, the Serial ATA interface, was launched in 2003.

This was actually the result of the developments and additional progress made in the field of interface technology. The SATA interface is therefore considered as an evolved step from ATAPI.

Attributes

Here are some of the characteristics and features of the Advanced Technology Packet Interface summarized for your better understanding:

ATAPI Commands

Usually, ATAPI uses a specific type of AT Attachments commands in a very small number. Out of these commands, the most significant one is the PACKET command (0xA0).

However, it also uses other commands such as the IDENTIFY PACKET DEVICE (0xA1) and a string of SCSI commands with different command bytes or OpCodes.

PACKET command (0xA0)

In this type of ATAPI command, every packet contains a command byte as well as 11 data bytes following it.

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For example, the following byte string is sent to the ATAPI device as a command for reading the table of contents:

uint8_t atapi_readtoc[]= { 0x43 /* ATAPI_READTOC */, 0, 1, 0, 0, 0, 0, 0, 12, 0x40, 0, 0};

Typically, the ATA PACKET command functions in three separate phases particularly in the PIO mode, such as:

On the other hand, in the Direct Memory Access mode, only the first two phases take place. As for the third phase, it is handled by the device itself with the help of the PCI drive controller.

IDENTIFY PACKET DEVICE command (0xA1)

In this command, a regular ATA PIO mode command is used at the time of initialization. This particular command is exactly the same as the ATA IDENTIFY command, with the only difference being in the return information. It is only about the ATAPI devices.

SCSI commands

Here are some of the names of SCSI commands along with their respective command bytes:

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SATA vs ATAPI

What are ATAPI Devices?

The list of ATA Packet Interface devices include CD-ROMs, CD-RW, CD-Recordable, tape drives, DVD, a few specific types of super-floppy drives such as ZIP and LS-120, different changers, DVD-ROM drives, magneto-optical drives, and SuperDisk drives.

Conclusion

The Advanced Technology Attachment interface is an extension of the AT protocol, which allows connecting many more devices to the computer apart from the hard drives.

They offer support for the IDE and SATA controllers to allow linking optical drives, tape drives, and others for a better performance output.