A Glossary of SCSI-Related Terms

ASPI (advanced SCSI programming interface)

A competitor for CAM, this has become the de facto standard.

ATA (AT attachment)

A 16-bit ISA specification for embedded devices. This is the most prevalent type of disk drive interface found on PCs today. It is sometimes incorrectly referred to as IDE.

CAM (common access method)

A programming standard that encapsulates the SCSI functions into a standardized calling interface.

CCS (Common Command Set)

A set of commands that were specified as part of the SCSI-1 specification and expanded in SCSI-2. CCS makes it easier to write device drivers for SCSI devices, because you can rely on there being a certain functionality in each class of device (e.g., hard drive, tape drive, and so on).

ESDI

Developed by Maxtor (San J ose, CA), this standard improved on the ST506 by providing better error checking and supporting more types of devices: hard drives, floppy drives, and tape drives. With ESDI, the interface is an integral part of the device, so the controller must be certified to work with the device. In addition, a device driver must be written for each ESDI controller/device combination.

IDE

Most of an IDE drive's intelligence is built into the drive itself. IDE refers to any drive with an integrated controller.

SASI (Shugart Associates system interface)

NCR and Shugart Associates (now Seagate Technology of Scotts Valley, CA) developed SASI in 1981. That same year, the ANSI X3T9 standards committee adopted SASI as a working document for an ANSI interface standard. The resulting ANSI standard was named SCSI. The current SCSI standard was finalized in 1986.

ST412/ST506 Interface

Shugart Associates developed this specification in 1980. In 1981, it was revised to include a feature called buffe red seek for the ST412 10-MB (formatted) hard drive. Many smaller-capacity hard drives on personal computers have used this interface. It has a limitation of 140 MB and a data transfer rate of 5 Mbps.

Terminator

A device that attaches to both ends of an electrical bus and prevents reflection or echoes of signals that reach the end of the bus. It also makes sure that the impedance is correct.